Rozprawy doktorskie na temat „Water stratification”

Six years of comprehensive data sets collected over the northern continental shelf and upper slope of the Gulf of Mexico during the LATEX-A and NEGOM-COH programs showed that low-oxygen waters (<2.4 mL·L-1) are found only in spring and summer and only in water depths between 10 and 60 m. Four regions in the northern Gulf show considerable differences in the occurrence of low-oxygen waters. Lowoxygen waters are observed almost exclusively in regions subject to large riverine influences: the Louisiana and Mississippi-Alabama shelves. Hypoxic waters (oxygen concentrations <1.4 mL·L-1) are found only over the Louisiana shelf. No low-oxygen water is found over the Florida shelf which has minimum riverine influence. Lowoxygen water is found at only one station on the Texas shelf; this is during spring when the volume of low-salinity water is at maximum. The distributions of low-salinity water influenced the different distributions of low-oxygen and hypoxic waters in the four regions. Low-oxygen occurrences are clearly related to vertical stratification. Lowoxygen occurred only in stable water columns with maximum Brunt-Väisälä frequency (Nmax) greater than 40 cycles·h-1. When Nmax exceeded 100 cycles·h-1 in summer over the Louisiana shelf, oxygen concentrations dropped below 1.4 mL·L-1, and the bottom waters became hypoxic. Salinity is more important than temperature in controlling vertical stratification. Locations where temperature influence was larger were found in summer in water depth greater than 20 m over the Louisiana shelf, along the near shore areas of the Mississippi-Alabama shelf west of 87ºW, and in the inner shelf waters of the Texas shelf. The extent of oxygen removal at the bottom of these stable water columns is reflected in the amount of remineralized silicate. Silicate concentrations are highest closest to the Mississippi River Delta and decrease east and west of the Delta. EOF analyses show that more than 65% of the oxygen variance is explained by the first mode. The amplitude functions of the first EOF modes of bottom oxygen, water column Brunt- Väisälä maxima, and bottom silicate are well correlated, indicating that much of the variance in bottom oxygen is explained by water column stratification and bottom remineralization.

Thesis (M.S.)--University of New Orleans, 2003.
Title from electronic submission form. "A thesis ... in partial fulfillment of the requirements for the degree of Master of Science in Environmental Engineering"--Thesis t.p. Vita. Includes bibliographical references.

Hypolimnetic anoxia can result in higher internal phosphorus (P) loads from the sediments to the water column, thereby increasing nutrient availability, making preventing anoxia a major goal for lake managers to improve water quality. Side-stream saturation (SSS), a type of hypolimnetic oxygenation system, has been developed to maintain oxygenated conditions at the sediments by withdrawing oxygen-depleted water from the hypolimnion to an on-site facility and injecting it with oxygen under high pressure before returning it to the hypolimnion. While this technique has been studied in select water bodies, to date it has not been successfully deployed in a shallow lake. This study investigated the effects of an SSS system deployed at Falling Creek Reservoir, a shallow drinking water reservoir located in Vinton, Virginia, USA. Specifically, we examined the effects of the SSS system on several chemical, physical, and biological response variables to ascertain the short-term impacts of hypolimnetic oxygenation on reservoir water quality. We found that the SSS system was successful in increasing dissolved oxygen concentrations in the reservoir hypolimnion without weakening stratification, warming the sediments, or increasing turbidity; however, we were unable to detect any short-term effects of SSS operation on P concentrations, P loading, pH, chlorophyll a, or algal density. Interestingly, we also observed an increase in oxygen demand in response to SSS operation, which must be taken into account when deploying oxygenation systems in the future. Continued monitoring is necessary to more completely assess the long-term impacts of SSS operation on water quality at Falling Creek Reservoir.
Master of Science

Cyanobacteria are a naturally occurring component of reservoir aquatic ecosystems. Given that some species possess the ability to control their depth within the water column, they have a competitive advantage over other species of photosynthetic organisms. This leads to the potential for cyanobacteria blooms, and because of taste and odor problems, as well as possible toxin production associated with certain species of cyanobacteria, these organisms can cause major problems in drinking water production. The Western Virginia Water Authority installed a solar-powered circulator in Falling Creek Reservoir, located in Bedford County, Virginia, in an attempt to limit the growth of these organisms through limiting light exposure by circulating them deeper within the reservoir. Experiments were performed during the summer of 2008 to quantify the effect of the circulator on the reservoir. Temperature, dissolved oxygen, water velocity, and photosynthetic yield were monitored before and during operation of the unit. The overall effect of the mixer was limited to the first 10 m immediately adjacent to the unit during the afternoon. The effect was stronger during the morning when the difference in density between the intake water and the surface of the reservoir was smaller, allowing the water to travel up to 80 m away from the unit. Although the circulator was only intended to mix and possibly deepen the epilimnion, the entire reservoir became mixed about two weeks after the circulator was put into operation. The reservoir is quite shallow, leading to a weak stratification that is easily disrupted by the operation of the circulator.
Master of Science

Electric hot water tanks play a pivotal role as demand response assets within the UK's energy system by storing heat when energy is inexpensive and delivering domestic hot water when it is required. This role will become increasingly important if non-dispatchable renewable energy sources are to play a bigger part in the energy mix. Historically, the design standards relating to hot water tanks have focused primarily on minimising heat losses. However, in addition to preserving energy, a hot water tank should preserve the availability of heat above a useful temperature for as long as possible to avoid energy usage during peak times when it is costly or carbon intensive. To do this, thermal stratification within hot water tanks must be promoted. Unfortunately, thermal stratification leads to conditions that are conducive to bacterial growth due to the hospitable temperatures that arise during operation. For this reason, question marks have arisen over the extent to which more flexible control strategies, designed to allow for increasing penetrations of intermittent renewable energy sources, might lead to the growth of pathogenic bacteria within hot water tanks. The objective of the work discussed in this thesis was to understand the extent to which there is a conflict between thermal stratification and bacterial growth in practice, whether this conflict can be resolved and the potential implications for electric hot water tanks operating on a time of use tariff. A small field study demonstrated that there is prolific bacterial growth within conventional electric cylinders and that this can be attributed to thermal stratification with a confidence of (P<0.01). Fitting a de-stratification pump, to enhance sanitary performance, resulted in a 19% decrease in the recovery of useable hot water above 43°C. Given that the tanks tested during the field study were made of copper, the consequences of alternative material choices on thermal performance were explored. It was found that the rate of useable hot water loss, due to de-stratification associated with thermal diffusion across the thermocline, could be reduced by a factor of 2.7 by making the tank liner wall from stainless steel instead of copper. Further numerical work indicated that this improvement in stratifying performance was most significant for small tanks with high aspect ratios. In addition to de-stratification that arises due to vertical conduction, de-stratification due to inlet mixing was reduced by up to 30% by installing a spiral diffuser into the base of a test cylinder. In addition, by lowering the immersion heating element to ensure there is sufficient heat transfer to the base of the cylinder, sterilising temperatures could be attained throughout the stored volume of water in the tank during heating. This showed that the conflict between thermal and sanitary performance within electric tanks could potentially be resolved. A bespoke tank, made from stainless steel and fitted with a diffuser, was built and subjected to typical draw cycles that reflect real world operation. These tests showed that more useable hot water could be delivered in comparison to a commercial off the shelf copper tank and consequently the utilisation of the Economy 7 time of use tariff would be enhanced.

This study investigates the behaviour of a vertically distributed source of buoyancy on the vertical stratification in a ventilated space, an important factor for determining indoor comfort when using displacement ventilation. A new theory describing the behaviour of this buoyancy source in a ventilated space was presented previous to this work, but experimental results were required in order to validate the theoretical and numerical modelling. The behaviour of this source of buoyancy on the stratification in a ventilated space is studied for a mechanically ventilated at steady-state and for a linearly stratified environment using salt water in a water scale model. The stratifications were measured using a traversing conductivity probe and then compared to theoretical predictions by numerically solving the plume equations for the new theory in Fortran. High quality measurements were produced, showing excellent repeatability for stratification measurements at steady-state with deviations of less than 1 %. Moreover, the linear stratifications had linear best fits up to R2 = 0.999 by using the double-bucket method. The theoretical predictions of the influence of the vertically distributed source correlate quantitatively with the mechanically ventilated experiments, showing good agreement to the strength of the ambient stratification, the position of the first front and the ventilation flow rate. The experimental results for the determination of the height of a horizontal intrusion of fluid into the linearly stratified environment were severely affected by the occurrence of gravity current at the ceiling of the ventilated space and comparisons to the new theory was not successful because of this. A two-layer stratification is observed where the upper layer had a weakly stratified density profile, instead of the multi-layer stratification predicted by previous researchers in their theoretical model. This discrepancy is due to smoothing and vertical turbulent mixing in the water scale model. It is recommended that the characteristic of the membrane that is used in the water scale model is investigated in relation to the gravity currents for future research.

ABSTRACT HEAT REMOVAL FROM A LARGE SCALE WARM WATER STORAGE Kayserilioglu, Yavuz Selim M.S., Department of Mechanical Engineering Supervisor: Prof. Dr. Rü
knettin Oskay August 2004, 88 Pages A preliminary experimental study was performed in order to investigate the charging and heat removal characteristics of a sensible heat storage. Two sets of experiments were performed at two aspect ratios. Heat removal processes of these two sets were different while the charging processes were similar. In the first set of experiments, after the charging of the storage unit with relatively warm water was complete, heat removal process was started with simple heat exchangers from different elevations within the storage while the charging of the storage unit was continued. In the second set of experiments, after the charging of the storage unit was complete, heat removal from the storage unit was started without further charging of the storage unit. Charging water was fed into the storage from the top of one side and relatively colder water was drained from the bottom of the opposite side. Internal heat exchangers were used for the heat removal. Vertical temperature profile developments during the charging and heat removal periods were investigated. Thermal stratification was observed in all experiments. Heat exchangers extracted heat from different elevations in different experiments and the trend was that more heat can be extracted in upper elevations. Comparable heat can be extracted from the same elevation of lower and higher aspect ratio. Keywords: Sensible Heat Storage, Heat Removal, Thermal Stratification, Warm Water Storage

Geophysical research has long been interdisciplinary, with many phenomena on the Earth's surface involving multiple, linked processes that are best understood using a combination of techniques. This is particularly true in the case of grain flows on sand dunes, in which the sedimentary stratification with which geologists are concerned arises from the granular processes investigated by physicists and engineers, and the water permeation that interests hydrologists and soil scientists determines the seismic velocities of concern to exploration geophysicists. In this dissertation, I describe four projects conducted for the degree of Doctor of Philosophy, using a combination of laboratory experimentation, fieldwork, numerical simulation, and mathematical modelling to link avalanching on dunes to its effects on stratification, on the permeation of water, and on seismic surveys. Firstly, I describe experiments on erodible, unbounded, grain piles in a channel, slowly supplied with additional grains, and I demonstrate that the behaviour of the consequent, discrete avalanches alternates between two regimes, typified by their size statistics. Reconciling the `self-organised criticality' that several authors have predicted for such a system with the hysteretic behaviour that others have observed, the system exhibits quasi-periodic, system-spanning avalanches in one regime, while in the other avalanches pass at irregular intervals and have a power-law size distribution. Secondly, I link this power-law size distribution to the strata emplaced by avalanches on bounded grain piles. A low inflow rate of grains into an experimental channel develops a pile, composed of strata in which blue-dyed, coarser grains overlie finer grains. Associating stopped avalanche fronts with the `trapped kinks' described by previous authors, I show that, in sufficiently large grain piles, mean stratum width increases linearly with distance downslope. This implies the possibility of interpreting paleodune height from the strata of aeolian sandstones, and makes predictions for the structure of avalanche-associated strata within active dunes. Thirdly, I discuss investigations of these strata within active, Qatari barchan dunes, using dye-infiltration to image strata in the field and extracting samples across individual strata with sub-centimetre resolution. Downslope increases in mean stratum width are evident, while measurements of particle size distributions demonstrate preferential permeation of water along substrata composed of finer particles, explaining the strata-associated, localised regions of high water content discovered by other work on the same dunes. Finally, I consider the effect of these within-dune variations in water content on seismic surveys for oil and gas. Having used high performance computing to simulate elastic wave propagation in the vicinity of an isolated, barchan sand dune, I demonstrate that such a dune acts as a resonator, absorbing energy from Rayleigh waves and reemitting it over an extensive period of time. I derive and validate a mathematical framework that uses bulk properties of the dune to predict quantitative properties of the emitted waves, and I demonstrate the importance of internal variations in seismic velocity, resulting from variations in water content.

Stratification of water in large reservoirs occurs in summer, or at anytime in hot climates where the water surface is exposed long-term to sunlight and the water surface is heated. Natural mixing will not occur due to the cooler and denser water always staying at the lower levels. Therefore, mechanical circulators are designed to prevent water quality problems related to stratification and depletion of dissolved oxygen. Impellers that produce the flow in mechanical circulators are available in different sizes and these impellers are designed to produce different flow rates. Due to hydraulic loadings, impellers have to be strong and durable. Loadings on impellers depend on their geometries and therefore, a durable impeller is a good combination of the use of correct materials and good geometry. Long and slender impellers are prone to failure when subjected to high hydrodynamic loadings. Nowadays, designers have very limited information on predicting the stresses on impellers and the deflection patterns of impellers because there are no design rules in designing these impeller blades and there is no such thing as "best geometry". A good impeller blade design is by guesswork and experience. In order to design the geometry that suits this application, trial-and-error finite element analyses have been conducted in this project to minimize stress levels on the blades. This research involves the use of finite element analysis (FEA) to predict stress and deflection of impeller blades used on large (5m diameter) ducted axial flow impellers as the first step in the design process. Then, based on the results, improvements have been done to the models until the final design was made. As far as the author has been able to determine, this has not been researched before. Finite Element Analysis has been used on wind turbine blades, rudders and hulls of boats but not on axial flow impeller blades of the type used in this project. For the purpose of this project, commercial finite element computer program packages STRAND6 and STRAND7 were used as the main analysis tools. A static line load increasing linearly with radius along the blade has been used to simulate the assumed hydrodynamic loading, and applied to all FEA blade models. The analysis results proved the stresses on blades are largely dependant on the blade geometry. From the analysis results, the author modified the stacking arrangement of the FEA elements in order to minimize both the tensile stresses and the displacements of the blades at the tip. Parametric studies have been done in order to obtain the best FEA impeller blade model.

Stratification of water in large reservoirs occurs in summer, or at anytime in hot climates where the water surface is exposed long-term to sunlight and the water surface is heated. Natural mixing will not occur due to the cooler and denser water always staying at the lower levels. Therefore, mechanical circulators are designed to prevent water quality problems related to stratification and depletion of dissolved oxygen. Impellers that produce the flow in mechanical circulators are available in different sizes and these impellers are designed to produce different flow rates. Due to hydraulic loadings, impellers have to be strong and durable. Loadings on impellers depend on their geometries and therefore, a durable impeller is a good combination of the use of correct materials and good geometry. Long and slender impellers are prone to failure when subjected to high hydrodynamic loadings. Nowadays, designers have very limited information on predicting the stresses on impellers and the deflection patterns of impellers because there are no design rules in designing these impeller blades and there is no such thing as "best geometry". A good impeller blade design is by guesswork and experience. In order to design the geometry that suits this application, trial-and-error finite element analyses have been conducted in this project to minimize stress levels on the blades. This research involves the use of finite element analysis (FEA) to predict stress and deflection of impeller blades used on large (5m diameter) ducted axial flow impellers as the first step in the design process. Then, based on the results, improvements have been done to the models until the final design was made. As far as the author has been able to determine, this has not been researched before. Finite Element Analysis has been used on wind turbine blades, rudders and hulls of boats but not on axial flow impeller blades of the type used in this project. For the purpose of this project, commercial finite element computer program packages STRAND6 and STRAND7 were used as the main analysis tools. A static line load increasing linearly with radius along the blade has been used to simulate the assumed hydrodynamic loading, and applied to all FEA blade models. The analysis results proved the stresses on blades are largely dependant on the blade geometry. From the analysis results, the author modified the stacking arrangement of the FEA elements in order to minimize both the tensile stresses and the displacements of the blades at the tip. Parametric studies have been done in order to obtain the best FEA impeller blade model.
Thesis (Masters)
Master of Philosophy (MPhil)
School of Engineering
Full Text

Diel vertical migration (DVM) can offer motile phytoplankton a competitive advantage over other phytoplankton species. DVM has been well documented in the harmful dinoflagellate, Karenia brevis; however, the extent to which changes in nutrient regimes and density stratification modify migration patterns has not been thoroughly investigated. A 2 m experimental column was constructed with sensors and sampling ports at four depths to obtain fluorescence and temperature measurements and discrete water samples. The environmental parameters of the experimental column represented temperature and nutrient conditions found on the West Florida Shelf (WFS), where Karenia blooms frequently occur. Results demonstrated a clear DVM pattern for K. brevis where surface aggregations occurred during light periods, and bottom aggregations occurred in dark periods. However, the rate and intensity of migration varied between experimental conditions. Injections of nutrient replete water at the surface and bottom did not appear to modify migratory behavior, in that a portion of the population resided at depth regardless of light or dark periods. Weak density stratification caused a delay in downward migration in dark periods, whereas strong density stratification caused a complete cessation of downward migration. In a weakly stratified environment with a bottom injected replete water mass, DVM patterns most closely replicate the pattern under weakly stratified conditions alone. Modifications in the natural DVM pattern of K. brevis with respect to varying environmental and nutrient conditions that occur on the WFS can have major implications current forecast model predictions, and for monitoring and mitigation strategies.

Phytoplankton mirrors changes in the environment and plays an important role in biogeochemical processes. Phytoplankton dynamics is the outcome of both autogenic succession and external disturbances. This thesis focused on the seasonal variation of water column stability and its effects on phytoplankton, particularly considering the influence of mixing events on phytoplankton development. Lake Erken is a dimictic lake with weak and often interrupted summer stratification, which represents an intermediate case between a polymictic lake and a lake with strong summer stratification. There are two diatom phases annually. The spring bloom is caused by pioneer centric diatoms, and the autumn diatom phase is dominated by meroplanktonic diatoms induced by turnover. A summer Cyanobacteria bloom – mainly Gloeotrichia echinulata, depended on the length and stability of stratification. Winter and spring air temperature is found to play an important role in the annual succession of phytoplankton by initiating changes in ice/snow-cover and lake thermal stability and setting the basic status. Instead of starting from zero, the vernal phytoplankton piles up on the overwintering community, this trans-annual ecological memory influences both the composition and diversity and taxonomic distinctness of spring phytoplankton. Water column stability during summer in Lake Erken is mainly influenced by wind-induced turbulence and internal seiches. As thermal stratification develops from early until late summer, variations in stability and gradual deepening of the thermocline depth influence phytoplankton dynamics directly by changing its distribution, and also indirectly by altering the nutrient and light availability. A new disturbance index (DI) was defined to quantify environmental stability/disturbance and tested well to indicate phytoplankton equilibrium status in two summer stratification periods. The concept of species and functional groups was generally used in this study. However, a next generation sequencing based approach was also tested and proved to provide an excellent candidate for revealing distribution patterns of phytoplankton in inland waters.

Les étangs sont des milieux aquatiques au coeur de problématiques environnementales dans les questions qualitatives et quantitatives de la ressource en eau. La température est un indicateur efficace dans ces mesures par sa réactivité et la capacité à se diffuser le plus en aval. L’étang est souvent considéré comme une boîte noire dans les études d’impact et la connaissance de son fonctionnement thermique devrait être le premier élément dans sa quantification. Dans cette étude, la prise en compte des volumes dans l’analyse thermique des 1 137 181 données thermiques horaires inédites, par le biais du bilan thermique, permet de mesurer et quantifier le fonctionnement global des étangs, distinct de celui des lacs. Le bilan thermique est un indicateur synthétique de l’ensemble des facteurs amenant et prélevant des calories au milieu et peut être utilisé dans son objectif premier de mesurer les échanges calorifiques au sein du plan d’eau et entre celui-ci et le milieu fluvial. L’hétérogénéité spatiale en étang dans l’aspect zonal, est influencée par l’effet de la force motrice du vent ou de l’environnement immédiat, la présence d’ombrage ou d’apports hydrologiques localisés. Un nouvel indicateur, le centre thermique, a été créé, prenant en compte les variations en trois dimensions du bilan thermique, de la stratification et la stabilité de plusieurs secteurs de l’étang afin de quantifier la dissociation des masses d’eau au sein du plan d’eau. L’intégration de la zonation thermique permet d’ouvrir de nouvelles perspectives de gestion afin de limiter l’impact thermique de l’étang à l’aval ou favoriser le développement de certaines espèces piscicoles thermosensibles. A partir de données météorologiques il est possible d’anticiper les zones d’expansion de chaleur dont les écarts peuvent être conséquents, mesurés à plus de 3°C sur un très petit étang lié à l’effet d’ombrage, ou encore à plus de 10 °C entre deux secteurs d’un grand étang multilobé sous l’influence des vents
Ponds are at the heart of environmental issues in terms of quality and quantity of water resources. Temperature is an effective indicator in these measurements because of its reactivity and the ability to diffuse the most downstream. The pond is often considered as a black box in studies and the knowledge of its thermal functioning should be the first element in its quantification. In this study, the inclusion of volumes in the thermal analysis of the 1,137,181 original hourly thermal data, through the heat budget, allows to measure and quantify the whole behavior of the ponds, distinct from that of the lakes. The heat budget is a synthetic indicator of all the factors that bring and extract calories from the environment and can be used in its primary objective to measure calorific exchanges within the water body and between the water body and the river environment. The spatial heterogeneity in the zonal aspect of the pond is influenced by the effect of the driving force of the wind or the surrounding environment, the presence of shade or hydrological inputs. A new indicator, the heat center, has been created, taking into account three-dimensional variations in the heat balance, stratification and stability of several areas of the pond in order to quantify the dissociation of water masses within the water body. The integration of thermal zoning opens up new management opportunities to reduce the thermal impact of the pond downstream or to promote the development of certain heat-sensitive fish species. From meteorological data it is possible to anticipate areas of heat expansion whose differences can be significant, measured at more than 3°C on a very small pond related to the shading effect, or at more than 10°C between two sectors of a large multi-block pond under the influence of winds

Los dispositivos de almacenamiento de energía térmica son ampliamente usados en diversos sistemas térmicos caracterizados por un desfase temporal entre la producción de energia y su consumo, como es el caso de los sistemas de energía solar térmica. El diseño optimizado de estos equipos puede representar un considerable aumento en el rendimiento térmico de la instalación de la cual forman parte. En la línea de optimización de sistemas y equipos térmicos, en los últimos años la Mecánica de Fluidos Computacional (CFD) se ha consolidado como una herramienta básica, proporcionando a investigadores e ingenieros un método para ensayar virtualmente sus diseños, disminuyendo los costes en términos de tiempo, recursos y personal. Es en esta línea se encuentran las principales aportaciones de esta tesis, la cual tiene como principal objetivo la simulación numérica de procesos de convección laminar en régimen transitorio y dominios cilíndricos para su aplicación al estudio de los fenómenos de transferencia de calor y dinámica de fluidos que tienen lugar en los tanques de almacenamiento de energía.

Se presenta la metodología seguida para la resolución de las ecuaciones gobernantes de la transferencia de calor y dinámica de fluidos en coordenadas cilíndricas, mostrando las principales particularidades de su discretización para este tipo de geometrías y se detalla el tratamiento realizado para resolver estas singularidades dentro del código numérico. Posteriormente, se expone la metodología para la solución de flujos transitorios e incompresibles y se realiza un riguroso proceso de verificación del código y las soluciones numéricas obtenidas.

Esta metodología se aplica al estudio del comportamiento de los tanques de almacenamiento de energía estratificados. Un aspecto básico del funcionamiento de estos equipos es la calidad de la energía almacenada. Esta calidad viene determinada por el grado de estratificación térmica, en la cual influyen diferentes factores como la mezcla que ocurre debido a las corrientes de fluido que entran durante los procesos de carga y descarga térmica y también debido al intercambio de calor con el ambiente. En este sentido, en este trabajo se analiza la estratificación térmica para diferentes condiciones de trabajo y configuraciones por medio de las simulaciones numéricas multidimensionales. Para medir el grado de estratificación se han tenido en cuenta diferentes parámetros y como resultado del estudio, se propone un parámetro adimensional basado en un análisis exergético. Esta exergía adimensional ha permitido comparar el funcionamiento de los tanques en las diferentes situaciones analizadas y se ha mostrado útil para cuantificar la calidad de la energía almacenada.

Por otra parte, se estudia el comportamiento térmico de los tanques de almacenamiento durante su modo de operación estático y considerando las pérdidas de energía al ambiente. Este estudio tiene como objetivo fundamental caracterizar el proceso de enfriamiento del fluido en tanques que forman parte de sistemas solares térmicos para el rango de bajas y medianas temperaturas. Se presenta la metodología seguida para el análisis, desde la identificación de los números adimensionales que definen el problema, la formulación de un modelo zonal para la predicción del comportamiento térmico, el estudio paramétrico llevado a cabo y el posterior post-proceso de los resultados con el objetivo de proporcionar los parámetros necesarios para alimentar el modelo zonal. El modelo propuesto, junto con las correlaciones obtenidas, predicen correctamente el comportamiento del fluido, constituyendo una alternativa interesante para reproducir el proceso de enfriamiento del fluido en los tanques durante largos periodos de tiempo.
Thermal storage devices are widely used in many thermal systems and applications that are characterised by the delay between energy production and consumption, such as thermal solar systems. The improvement in their design and optimisation is a key aspect in the thermal optimisation of the system, where a good preformance of the storage tank can represent a considerable increase in the overall efficiency of the installation. In the subject of optimisation of thermal equipment, Computational Fluid Dynamics have been consolidated as an indispensable tool providing researchers and engineers with a method to test virtually their prototypes with low effort in time, personnel and resources. This thesis is focused in the numerical simulation of unsteady laminar convection in cylindrical domains and its application to the study of the heat transfer and fluid flow that take place in stratified storage tanks.

The first part of this document is devoted to present the methodology followed for the numerical resolution of the governing equation of heat and fluid flow in cylindrical coordinates. The main particularities of the discretisation of the equations in these geometries, as well as the solution procedure for incompressible and transient flow problems are also presented. Special emphasis is given to the verification of the code, the appropriateness of the discretisation adopted and the verification of the numerical solution obtained.

The second part of this thesis is focused on the study of the heat transfer and fluid flow phenomena that take place in stratified storage tanks, including the performance measures and modeling efforts of these devices. The quality of the energy stored is determined by the degree of the thermal stratification of the storage tank, which is affected by several factors such as the mixing due to the inlet streams during load and unload, the heat losses to the environment, among others. In this sense, thermal stratification analysis is carried out by means of the virtual prototyping of the tanks for different working conditions and configurations. In order to measure the performance of the tanks, different parameters are considered. The analysis led to the proposition of a new exergy-based parameter as a tool for assessing and comparing storage tanks. The usefulness of this parameter for quantifying the quality of the energy stored is also shown.

Furthermore, the thermal behaviour of storage tanks during the static mode of operation considering the heat losses to the environment is also analysed. The study is addressed to characterise the cool down of the fluid inside storage tanks for solar thermal systems in the low-to-medium temperature range. The methodology followed, from the identification of the significant non-dimensional parameters that define the problem, the formulation of a zonal prediction model, a parametric numerical study by means of detailed multidimensional CFD computations and the post-processing of the results in order to feed the global model are exposed in detail. Zonal model presented, together with the correlations given are in good agreement with the numerical results and constitute an alternative for the prediction of the long-term performance of the storage tanks during the cooling process.

Water from Mantua reservoir has, during some years, exhibited reddish-brown staining when used by Brigham City for irrigation. I propose that seasonal fluctuations in the reservoir chemistry create an environment conducive to dissolving iron from the iron-rich sediments, which subsequently precipitate during irrigation, resulting in a staining event. These conditions are produced by chemical and biological decomposition of organic matter, coupled with isolation of the hypolimnetic waters, which results in seasonal low concentrations of dissolved oxygen in these waters. Under these specific circumstances, anaerobic conditions develop creating a geochemical environment that causes iron and manganese reduction from Fe(III) to Fe(II) and Mn(IV) to Mn(II), respectively. These reducing conditions facilitate reduction-oxidation (redox) chemical reactions that convert insoluble forms of iron and manganese found in the reservoir sediments into more soluble forms. Consequently, relatively high amounts of dissolved iron and manganese are generated in the bottom waters immediately adjacent to the benthic sediments of the reservoir. Water withdrawn from a bottom intake pipe during these periods introduces iron-rich water into the distribution system. When this water is exposed to oxygen, reoxidation shifts redox equilibrium causing precipitation of soluble Fe(II) and Mn(III) back to highly insoluble Fe(III) and Mn(IV). The precipitant appears on contact surfaces as the aforementioned ferric stain. This research focuses specifically on the iron chemistry involved and evaluates this hypothesis using various measurements and models including field data collection, computer simulations, and bench-scale testing to validate the processes proposed.

Resumo: Considerando a grande importância da bacia do Alto do Rio Sorocaba para a região de Sorocaba, seja para o abastecimento da população, geração de energia elétrica, irrigação e usos industriais, este trabalho teve como objetivo principal avaliar a qualidade da água do reservatório de Itupararanga. O estudo foi desenvolvido pela da geração de um banco de dados georreferenciado, avaliação da qualidade de água no seu gradiente espacial (horizontal e vertical) e temporal (épocas de seca e chuvosa), visando conhecer o comportamento de alguns elementos e compostos na coluna d'água e sua distribuição neste reservatório, correlacionando-os ao uso e ocupação do solo adjacente. Assim, de acordo com os resultados obtidos no gradiente horizontal (montante-jusante) na época de seca 90% dos pontos estavam eutrofizados (IET > 54) e na época de chuva 60%. No gradiente vertical (lâmina d'águafundo) observou-se que a distribuição de elementos metálicos e nutrientes variaram de acordo com o pH e presença de clorofila-a, indicando que a eutrofização do reservatório altera as condições de crescimento de algas que por sua vez afeta a estratificação de elementos na coluna d'agua. Portanto, entende-se que são necessárias ações voltadas ao planejamento do uso e ocupação do solo e gerenciamento integrado desta importante bacia hidrográfica localizada no interior paulista.
Abstract: Considering the great importance of upper Sorocaba basin to the Sorocaba region to water supply, electric generation, irrigation and industrial uses, this work has the main objective to evaluate the water quality of Itupararanga reservoir. The study was conducted with the generation of a georreferenced data base, the water quality evaluation in the spacial gradient (horizontal and vertical distribuition) and temporal (dry and wet climate), trying to know the comportament of some elements and solutions in water column in the reservoir, trying to make the correlation between the data and land use. The results show that in horizontal gradient (upstream - downstream) in the dry period, 90% of collecting points are eutrophic (IET > 54), in the wet period, 60%. In vertical gradient (up - bottom) was observed that the distribuition of some metallic elements and some compounds varied in accordance with pH and chlorophyll-a, indicating that the reservoir eutrophization shifts the algal growing, that causes, with the temperature, stratifies elements in water column. Actions to plan the land use in this watershed are needed to reduce the environment and water quality degradation, making a integrated managing of this important watershed in countryside of São Paulo State.
Orientador: Fabiano Tomazini da Conceição
Coorientador: Washington Barbosa Leite Júnior
Banca: Rodrigo Braga Moruzzi
Banca: Alexandre Marco da Silva
Mestre

Made available in DSpace on 2014-06-11T19:26:14Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-06-22Bitstream added on 2014-06-13T18:54:23Z : No. of bitstreams: 1 pedrazzi_fjm_me_rcla.pdf: 6663596 bytes, checksum: 0e9d03b7b531f91d8f6add54957a1a89 (MD5)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Considerando a grande importância da bacia do Alto do Rio Sorocaba para a região de Sorocaba, seja para o abastecimento da população, geração de energia elétrica, irrigação e usos industriais, este trabalho teve como objetivo principal avaliar a qualidade da água do reservatório de Itupararanga. O estudo foi desenvolvido pela da geração de um banco de dados georreferenciado, avaliação da qualidade de água no seu gradiente espacial (horizontal e vertical) e temporal (épocas de seca e chuvosa), visando conhecer o comportamento de alguns elementos e compostos na coluna d´água e sua distribuição neste reservatório, correlacionando-os ao uso e ocupação do solo adjacente. Assim, de acordo com os resultados obtidos no gradiente horizontal (montante-jusante) na época de seca 90% dos pontos estavam eutrofizados (IET > 54) e na época de chuva 60%. No gradiente vertical (lâmina d’águafundo) observou-se que a distribuição de elementos metálicos e nutrientes variaram de acordo com o pH e presença de clorofila-a, indicando que a eutrofização do reservatório altera as condições de crescimento de algas que por sua vez afeta a estratificação de elementos na coluna d’agua. Portanto, entende-se que são necessárias ações voltadas ao planejamento do uso e ocupação do solo e gerenciamento integrado desta importante bacia hidrográfica localizada no interior paulista.
Considering the great importance of upper Sorocaba basin to the Sorocaba region to water supply, electric generation, irrigation and industrial uses, this work has the main objective to evaluate the water quality of Itupararanga reservoir. The study was conducted with the generation of a georreferenced data base, the water quality evaluation in the spacial gradient (horizontal and vertical distribuition) and temporal (dry and wet climate), trying to know the comportament of some elements and solutions in water column in the reservoir, trying to make the correlation between the data and land use. The results show that in horizontal gradient (upstream – downstream) in the dry period, 90% of collecting points are eutrophic (IET > 54), in the wet period, 60%. In vertical gradient (up – bottom) was observed that the distribuition of some metallic elements and some compounds varied in accordance with pH and chlorophyll-a, indicating that the reservoir eutrophization shifts the algal growing, that causes, with the temperature, stratifies elements in water column. Actions to plan the land use in this watershed are needed to reduce the environment and water quality degradation, making a integrated managing of this important watershed in countryside of São Paulo State.

Rural communities have, for much of history, been left with inadequate or no water service. This is because the traditional state/private dichotomy of water provision is inadequate for addressing the unique needs of small, isolated communities. Drawing from the Common-Pool Resource literature, co-management arose in recent decades as a solution to address this pandemic of rural water exclusion. In Costa Rica, co-management takes the form of community water associations known as ASADAS. This thesis explores the successes and challenges of ASADAS through the use of three case study communities. Using interviews, surveys, water sampling and national legislation in addition to secondary sources, this thesis seeks to understand the possibilities and limits of employing co-management as a tool for achieving the human right to water in Costa Rica and around the globe.

As the case with most countries across Latin America, unprecedented migration to urban areas has strained city infrastructure systems. More particularly, the region faces a pressing crisis of water security, where rapid urbanization has outpaced water sector development. This thesis addresses the water infrastructure reform in El Alto and La Paz, Bolivia, focusing on strategies to better promote water access for the peri-urban poor. The research investigates the level of progressivity of water service expansion and pricing regimes: in other words, does the present model of water distribution positively improve the lives of the poorest groups? By investigating these social dimensions of water management, this study brings perspectives on the broader dialogue on Bolivia’s economic development, along with issues of participatory governance. Resumen: Como es el caso en muchos países latinoamericanos, la migración a áreas urbanas a niveles sin precedentes ha superado la capacidad de infraestructura. Concretamente, la región se enfrenta a una urgente crisis en la seguridad de agua potable dado que la rápida urbanización ha sobrepasado el desarrollo de este sector. Esta tesis aborda la reforma de la infraestructura de agua potable en El Alto y La Paz, Bolivia, enfocando en las estrategias para mejorar el acceso a agua por parte de los residentes periurbanos pobres. La investigación averigua el nivel de progresividad de los regímenes de precios y expansión de servicios de agua potable. En otras palabras, ¿contribuye el actual modelo de distribución de agua al mejoramiento de la vida de los grupos más desfavorecidos? Al investigar estas dimensiones sociales en el manejo de agua potable, este estudio ofrece perspectivas en cuanto al diálogo amplio del desarrollo económico de Bolivia, así como asuntos de gobernanza participativa.

Wärmespeicher tragen bei optimierter Integration in Wärme- und Kälteversorgungsanlagen zur Einsparung von installierter Erzeugerleistung, Brennstoffeinsatz und Betriebskosten bei. Leider treten in Wärmespeichern oft noch beachtliche Verluste auf und das Potenzial zur Kosten- und Energieeinsparung wird nicht vollständig ausgeschöpft. Dabei spielen nicht nur Wärmeverluste an die Umgebung, sondern vor allem auch innere Verluste im Speicher eine Rolle. Schwerpunkte der vorliegenden Arbeit sind die Beschreibung der einzelnen Verluste an Wasserwärmespeichern, die Ermittlung ihrer Ausmaße abhängig von der konstruktiven Gestaltung und der Betriebsweise des Speichers sowie die Auswirkungen der Verluste auf einen vorgelagerten Wärmeerzeuger und den Einsatz von Primärenergie. Die Ergebnisse basieren auf umfangreichen Speichermodellierungen mit dem CFD-Code Fluent sowie experimentellen Untersuchungen an drei Testspeichern. Der quantitative Vergleich der Verluste für ausgewählte Beispiele zeigt bestehende Defizite sowie die Potenziale für die Verbesserung der Konstruktion neuer Wasserwärmespeicher auf
If hot water storage tanks are optimally integrated in heat or cold supply systems, they contribute to a reduction of required capacity, fuel and operation costs. Unfortunately, even today remarkable heat losses and internal losses occur in hot water storage tanks. The potential for cost and energy reductions is not completely utilized yet. Here, not only heat losses to the ambience, but also internal losses play a decisive role. Main focus of the presented work is the description of the single losses at hot water storage tanks and the determination of the correlation between the losses, the tank design and the mode of operation. Furthermore the effects of the losses in the tank on the efficiency of different types of heat generators and the input of primary energy into the system have been examined. The results are based on extended numerical modeling with the CFD-code Fluent as well as experimental test with three storage tanks. The quantitative comparison of the losses for selected examples shows the current shortcomings but even the potential for an optimized hot water storage tank design

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
The construction of several reservoirs to meet multiple uses has become essential to human societies. The Vacacaí Mirim s reservoir is used primarily for human supply, accounting for 40% of the Santa Maria water supply. The exam of this reservoir provides a fundamental basis for managing its water quality and its watershed. The objective of this research is to evaluate the variability of the water quality and the trophic status of the Vacacaí Mirim s reservoir. Eight field campaigns were performed between 2010 and 2011, and the water samples were taken at four distributed points along the reservoir and one point located upstream the main tributary river. On the reservoir s sampling points were collected samples from surface (S) and depth (P). The main water quality parameters evaluated were: Water Temperature, pH, Electrical Conductivity, Turbidity, DO, BOD5, COD, TSS, TDS, E. coli, Chlorophyll-a, Ammonium, Nitrite, Nitrate, Total Phosphorus. The trophic status was monitored considering the levels of phosphorus, chlorophyll-a and some biological indicators. The Vacacaí Mirim s reservoir presented a long period of thermal stability, being more or less consistent to the seasonal period, with full circulation only in winter, conferring its classification as warm monomictic. The concentration of most parameters analyzed varied more on a time level than a space level. The parameter that inspires greater concern is the number of E. coli, which in 16% of the time exceeds the limits for class 3 of CONAMA Resolution No. 357/05 making the water unsuitable for this purpose. The correlation analysis also showed strong relationship between some environmental hydrological variables with some parameters of quality. The seasonal variation of the values of the TSI and biological indicators, suggest the Vacacaí Mirim s reservoir as a mesotrophic ecosystem, sometimes tending to eutrophic, so showing an anthropogenic influence. It is suggested to the government, organizations and population, the proper attention to the degradation processes, being necessary the watershed land use control and ordination, the riparian vegetation reestablishment, as well as an adjustment on the effluents emission through appropriate treatment.
A construção de reservatórios visando atender usos múltiplos tornou-se essencial para as sociedades humanas. O reservatório do Vacacaí Mirim é utilizado primordialmente para abastecimento humano, sendo responsável por 40% do fornecimento de água para Santa Maria. O seu estudo proporciona uma base fundamental para o gerenciamento da qualidade de suas águas e de sua bacia hidrográfica. Assim, o objetivo desta pesquisa é avaliar a variabilidade da qualidade da água e do estado trófico do reservatório do Vacacaí Mirim. Foram realizadas oito campanhas de campo entre 2010 e 2011, sendo as coletas de água amostradas em quatro pontos distribuídos ao longo do reservatório e um ponto localizado à montante, no principal rio afluente. Nos pontos do reservatório foram coletadas amostras de superfície (S) e profundidade (P). Em laboratório, as características de qualidade da água foram avaliadas periodicamente, através dos parâmetros: temperatura da água, pH, condutividade elétrica, turbidez, OD, DBO5, DQO, SST, SDT, E. coli, Clorofila-a, Amônia, Nitrito, Nitrato, Fósforo Total e outros Íons. O estado trófico foi avaliado levando em consideração os teores de Fósforo, Clorofila-a e alguns indicadores biológicos. O reservatório do Vacacaí Mirim apresentou um longo período de estabilidade térmica, em maior ou menor grau coerentemente com o período sazonal, apresentando circulação completa somente no inverno, conferindo sua classificação como monomítico quente. As concentrações da maioria dos parâmetros analisados apresentaram maior variação a nível temporal que espacial. O parâmetro que inspira maior preocupação é o número de E. coli, que em 16% do tempo ultrapassa os limites estabelecidos para a classe 3 da Res. CONAMA N°357/05 tornando a água imprópria para este fim. As análises de correlação também mostraram forte relação entre algumas variáveis hidrológicas ambientais com alguns parâmetros de qualidade. A variação sazonal dos valores do IET e indicadores biológicos, sugerem o reservatório do Vacacaí Mirim como um ecossistema mesotrófico, tendendo algumas vezes à eutrofia, já evidenciando influência antropogênica. Sugere-se ao poder público, às organizações e à população, a devida atenção aos processos de degradação, sendo necessário o controle e a ordenação do uso do solo na bacia, o reestabelecimento da vegetação ripariana, bem como uma adequação nos lançamentos de efluentes através de um tratamento adequado.

Orientadores: Elizabete Jordão, Moysés Alberto Navarro
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
Made available in DSpace on 2018-08-20T11:58:32Z (GMT). No. of bitstreams: 1 Rezende_HugoCesar_D.pdf: 10614958 bytes, checksum: aa2b2ce9d9ec481bd44e74cc217832a2 (MD5) Previous issue date: 2012
Resumo: O escoamento monofásico termicamente estratificado ocorre em tubulações horizontais onde duas camadas diferentes de um mesmo líquido escoam separadamente, sem que ocorra mistura significativa entre as camadas, devido às baixas velocidades e à diferença de densidade (e temperatura). As consequências desse fenômeno não foram consideradas no projeto da maioria das centrais nucleares atualmente em operação. Entretanto, em alguns componentes de centrais nucleares, as diferenças de temperatura podem atingir cerca de 200 °C em uma região bastante estreita nas proximidades da interface entre as camadas de água fria e quente. Nesta condição, as fortes tensões geradas pelas diferenças de dilatação podem comprometer a integridade estrutural e a vida útil de tubulações relacionadas aos sistemas de segurança dessas centrais nucleares. Com o objetivo de estudar o fenômeno da estratificação foi projetada e construída a Instalação de Testes de Estratificação Térmica (ITET), tendo sido realizada uma série de experimentos simulando o bocal de injeção do gerador de vapor de uma central nuclear tipo PWR. Foram estudadas a evolução e as configurações de escoamento em regime de estratificação térmica, assim como a influência do número de Froude nos gradientes de temperatura, na posição da interface entre as camadas de água fria e de água quente e no aparecimento de oscilações desta interface. Os experimentos foram realizados com número de Froude variando de 0,02 a 0,4...Observação: O resumo, na íntegra, poderá ser visualizado no texto completo da tese digital
Abstract: One phase thermally stratified flows occur when two different layers of the same liquid at different temperatures flow separately in horizontal pipes without appreciable mixing due to the low velocities and difference in density (and temperature). The phenomenon was not considered in the design stage of most of the operating nuclear power plants. However, temperature differences of about 200 °C have been found in a narrow band around the hot and cold water interface in components under stratified flows. Loadings due to this phenomenon affected the integrity of safety related piping systems. The Thermal Stratification Test Facility (ITET), built to allow the experimental simulation of the thermal stratification, is presented so as the results of some experiments simulating one phase thermally stratified flows in geometry and flow condition similar to a nuclear reactor steam generator nozzle. They have the objective of studying the flow configurations and understanding the evolution of the of thermal stratification process. The driving parameter considered to characterize flow under stratified regime due to difference in specific masses is the Froude number. Different Froude numbers, from 0.02 to 0.4, were obtained in different testes by setting injection cold water flow rates and hot water initial temperatures as planned in the test matrix. Results are presented showing the influence of Froude number on the hot and cold water interface position, temperature gradients and striping phenomenon...Note: The complete abstract is available with the full electronic document
Doutorado
Sistemas de Processos Quimicos e Informatica
Doutor em Engenharia Química

A humanidade tem uma importante ligaÃÃo histÃrica com a Ãgua em especial com os Ecossistemas AquÃticos Continentais (EACs) No mundo existem cerca de 1 386 milhÃes de km3 de Ãgua sendo apenas 2 5% Ãgua doce à de extrema importÃncia o conhecimento das variÃveis fÃsico-quÃmicas da Ãgua para prever de forma antecipada os fenÃmenos de estratificaÃÃo e desestratificaÃÃo tÃrmica Assim podendo evita perdas financeiras em empreendimentos aquÃcolas O presente trabalho teve como objetivos determinar quais efeitos a tilapicultura em tanques redes realizada na Fazenda Capo Grande (Pentecoste CearÃ) exerce sobre os parÃmetros da Ãgua subsuperficial e de fundo no cultivo e monitorar sistematicamente as alteraÃÃes fÃsico-quÃmicas nictimerais causadas pelas alteraÃÃes meteorolÃgicas locais O trabalho foi realizado na Piscicultura Campo Grande localizada no AÃude Publico Pereira de Miranda localizado em Pentecoste (Cearà â Brasil) Foram escolhidos dois pontos de coletas com a mesma profundidade e caracterÃsticas semelhantes (PC â Ponto controle localizado a 50 m dos tanques-rede; PTR â Ponto nos Tanques-Rede localizado entre os tanques-rede) Os dados meteorolÃgicos foram obtidos atravÃs da FUNCEME e da EstaÃÃo MeteorolÃgica da UFC As campanhas ocorriam a cada 21 dias se iniciaram no dia 24/03/2012 e foram finalizadas no dia 07/07/2012 Coletava-se Ãguas de sub-superfÃcie (0 30 m) e de fundo (3 90 m) nos dois pontos e em horÃrios diferentes (6 12 18 e 24h00min) Ainda no local foram medidos a temperatura da Ãgua pH e ocorria a fixaÃÃo do oxigÃnio pelo mÃtodo de Winckler Em laboratÃrio foram medidos a condutividade elÃtrica oxigÃnio dissolvido alcalinidade total dureza total salinidade nitrogÃnio amoniacal total nitrito ferro II e fÃsforo dissolvido A transparÃncia da Ãgua foi medida com um disco de secchi Cada campanha gerou 324 resultados de qualidade de Ãgua totalizando 1944 resultados no fim do trabalho Concluiu-se que a Piscicultura Campo Grande eutrofizou o meio de forma insignificante que a alteraÃÃo da qualidade de Ãgua se deu principalmente na Ãgua de fundo ocorreram estratificaÃÃes tÃrmicas na Ãrea da piscicultura mas nem sempre ocorreu à mistura total da massa de Ãgua a dispersÃo de resÃduos foi muito baixa mantendo-se no perÃmetro dos tanques-rede e a qualidade da Ãgua pode ser organizada da seguinte forma em ordem crescente de qualidade de Ãgua (da pior para a melhor Ãgua): 1 â Ãgua de fundo dos tanques-rede; 2 â Ãgua de fundo do ponto-controle; 3 â Ãgua subsuperficial dos pontos controle e tanques-rede
Mankind has an important historical connection with the water especially with Continental Aquatic Ecosystems (CAEs) Worldwide there are about 1386 million km3 of water This value may seem absurdly large almost unimaginable but only a small portion of this amount is freshwater and a smaller portion is still available for consumption by humans This study aimed to determine the effects of tilapia culture in cages held at Fazenda Campo Grande (Weir Pereira de Miranda Pentecost CearÃ) the quality of surface and bottom of the cultivation area and systematically monitor the physical-chemical changes nictimerais changes caused by local weather The study was conducted at Aquaculture Campo Grande located in Weir Public Pereira de Miranda located in Petecoste (Cearà - Brazil) Have chosen two stations (PC - Control Point; PTR - Point in Tanks-Net) Were chosen due to location (50 m away) and divide the similar physical characteristics (depth distance from shore etc ) Meteorological data were obtained from FUNCEME and the the Meteorological Station of Universidade Federal do Cearà The campaigns took place every three weeks and began on 24/03/2012 and were finalized on 07/07/2012 Them were collected waters of sub-surface and bottom in two points and at different times (6 12 18 and 24h00min) Even at the site were measured water temperature pH and oxygen fixation occurred by Winckler method In the laboratory were measured electrical conductivity dissolved oxygen total alkalinity total hardness salinity total ammonia nitrogen nitrite iron II and dissolved phosphorus The water clarity was measured with a Secchi disk Each campaign has generated 324 results in water quality total 1944 results at the end of the work In the end it was concluded that the fish farming Campo Grande eutrophication medium so insignificant that the change in water quality is mainly in the bottom water thermal stratification occurred in fish but there was not always a total mixture of the water body waste dispersion was very low keeping the perimeter of the cages and water quality can be organized as follows in order of increasing water quality (from worse to best water): 1 - bottom water of net cages; 2 - bottom water-point control; 3 - sub-surface water of the control points and net cages

Orientador: Alcides Padilha
Banca: Vicente Luiz Scalon
Banca: Ricardo Fortes de Miranda
Resumo: Este estudo apresenta uma análise numérica dos campos de temperaturas e velocidades d'água durante seu processo de aquecimento via calor sensível no interior de um armazenador térmico cilíndrico, aquecido lateralmente e adiabático em seu topo e base, visando o estudo da condição de operação de um aquecedor de água coletor solar-armazenador integrados (ICSSWH - Integrated Collector-Storage Water Heater). Em uma segunda análise a influência de um defletor interno é estudada pela definição dos campos de velocidades e temperaturas da água. A abordagem numérica é realizada a partir de um modelo bidimensional, transiente, não linear e em coordenadas cilíndricas, discretizada pela técnica de elementos finitos. A construção do modelo é obtida numericamente através de um código computacional desenvolvido em linguagem de programação C. Os resultados numéricos são validados. Análises transientes dos campos de velocidades e temperaturas bem como das temperaturas de mistura e velocidade de carregamento, com e sem parede interna direcionada (defletor interno) são realizadas com a finalidade de estudar a inlfuência da referida parede na convecção livre nessas condições.
Abstract: This study shows a numerical analysis of the temperature and speed fields of water during the process of heating through sensible heat in the interior of a cylindric thermal storage, heated laterally and with adiabatics top and base, in order to study the operational conditions of an integrated collector-storage solar water heater (ICSSWH). In a second analysis a model with an internal baffle is created and temperature and velocity fields are analysed. The numerical study is done taking into consideration a bidimensional, transient non linear research in cylindric coordenates, discretized by the technique of finite elements. Its solution is obtained numerically through a computational code developed in a C programming language. The numerical results are validated. A transient analysis of the spped and temperature fields so as of the mixing temperatures and the charging speed, with or without the infernal baffle are carried out taking into account the aim of studying the influence of the so called wall in the free convection of those conditions.
Mestre

Wärmespeicher tragen bei optimierter Integration in Wärme- und Kälteversorgungsanlagen zur Einsparung von installierter Erzeugerleistung, Brennstoffeinsatz und Betriebskosten bei. Leider treten in Wärmespeichern oft noch beachtliche Verluste auf und das Potenzial zur Kosten- und Energieeinsparung wird nicht vollständig ausgeschöpft. Dabei spielen nicht nur Wärmeverluste an die Umgebung, sondern vor allem auch innere Verluste im Speicher eine Rolle. Schwerpunkte der vorliegenden Arbeit sind die Beschreibung der einzelnen Verluste an Wasserwärmespeichern, die Ermittlung ihrer Ausmaße abhängig von der konstruktiven Gestaltung und der Betriebsweise des Speichers sowie die Auswirkungen der Verluste auf einen vorgelagerten Wärmeerzeuger und den Einsatz von Primärenergie. Die Ergebnisse basieren auf umfangreichen Speichermodellierungen mit dem CFD-Code Fluent sowie experimentellen Untersuchungen an drei Testspeichern. Der quantitative Vergleich der Verluste für ausgewählte Beispiele zeigt bestehende Defizite sowie die Potenziale für die Verbesserung der Konstruktion neuer Wasserwärmespeicher auf.
If hot water storage tanks are optimally integrated in heat or cold supply systems, they contribute to a reduction of required capacity, fuel and operation costs. Unfortunately, even today remarkable heat losses and internal losses occur in hot water storage tanks. The potential for cost and energy reductions is not completely utilized yet. Here, not only heat losses to the ambience, but also internal losses play a decisive role. Main focus of the presented work is the description of the single losses at hot water storage tanks and the determination of the correlation between the losses, the tank design and the mode of operation. Furthermore the effects of the losses in the tank on the efficiency of different types of heat generators and the input of primary energy into the system have been examined. The results are based on extended numerical modeling with the CFD-code Fluent as well as experimental test with three storage tanks. The quantitative comparison of the losses for selected examples shows the current shortcomings but even the potential for an optimized hot water storage tank design.

Made available in DSpace on 2016-04-01T17:54:39Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-08-10. Added 1 bitstream(s) on 2016-04-01T18:00:20Z : No. of bitstreams: 1 000505772.pdf: 2673100 bytes, checksum: 0b1ec10e248621594ebb61317344d2af (MD5)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Este estudo apresenta uma análise numérica dos campos de temperaturas e velocidades d'água durante seu processo de aquecimento via calor sensível no interior de um armazenador térmico cilíndrico, aquecido lateralmente e adiabático em seu topo e base, visando o estudo da condição de operação de um aquecedor de água coletor solar-armazenador integrados (ICSSWH - Integrated Collector-Storage Water Heater). Em uma segunda análise a influência de um defletor interno é estudada pela definição dos campos de velocidades e temperaturas da água. A abordagem numérica é realizada a partir de um modelo bidimensional, transiente, não linear e em coordenadas cilíndricas, discretizada pela técnica de elementos finitos. A construção do modelo é obtida numericamente através de um código computacional desenvolvido em linguagem de programação C. Os resultados numéricos são validados. Análises transientes dos campos de velocidades e temperaturas bem como das temperaturas de mistura e velocidade de carregamento, com e sem parede interna direcionada (defletor interno) são realizadas com a finalidade de estudar a inlfuência da referida parede na convecção livre nessas condições.
This study shows a numerical analysis of the temperature and speed fields of water during the process of heating through sensible heat in the interior of a cylindric thermal storage, heated laterally and with adiabatics top and base, in order to study the operational conditions of an integrated collector-storage solar water heater (ICSSWH). In a second analysis a model with an internal baffle is created and temperature and velocity fields are analysed. The numerical study is done taking into consideration a bidimensional, transient non linear research in cylindric coordenates, discretized by the technique of finite elements. Its solution is obtained numerically through a computational code developed in a C programming language. The numerical results are validated. A transient analysis of the spped and temperature fields so as of the mixing temperatures and the charging speed, with or without the infernal baffle are carried out taking into account the aim of studying the influence of the so called wall in the free convection of those conditions.

The shallow water configuration of the gulf of Trieste allows the propagation of the stress due to wind and waves along the whole water column down to the bottom. When the stress overcomes a particular threshold it produces resuspension processes of the benthic detritus. The benthic sediments in the North Adriatic are rich of organic matter, transported here by many rivers. This biological active particulate, when remaining in the water, can be transported in all the Adriatic basin by the basin-wide circulation. In this work is presented a first implementation of a resuspension/deposition submodel in the oceanographic coupled physical-biogeochemical 1-dimensional numerical model POM-BFM. At first has been considered the only climatological wind stress forcing, next has been introduced, on the surface, an annual cycle of wave motion and finally have been imposed some exceptional wave event in different periods of the year. The results show a strong relationship between the efficiency of the resuspension process and the stratification of the water column. During summer the strong stratification can contained a great quantity of suspended matter near to the bottom, while during winter even a low concentration of particulate can reach the surface and remains into the water for several months without settling and influencing the biogeochemical system. Looking at the biologic effects, the organic particulate, injected in the water column, allow a sudden growth of the pelagic bacteria which competes with the phytoplankton for nutrients strongly inhibiting its growth. This happen especially during summer when the suspended benthic detritus concentration is greater.

Internal gravity waves play a fundamental role in the dynamics of stably stratified regions of the atmosphere and ocean. In addition to the radiation of momentum and energy remote from generation sites, internal waves drive vertical transport of heat and mass through the ocean by wave breaking and the mixing subsequently produced. Identifying regions where internal gravity waves contribute to ocean mixing and quantifying this mixing are therefore important for accurate climate and weather predictions. Field studies report significantly enhanced measurements of turbulence near 'rough' ocean topography compared with those recorded in the ocean interior or near more gradually varying topography (e.g. Toole et al. 1997, J. Geophys. Res. 102). Such observations suggest that interaction of waves with rough topography may act to skew wave energy spectra to high wavenumbers and hence promote wave breaking and fluid mixing. This thesis examines the high wavenumber scatter and spatial partitioning of wave energy at 'rough' topography containing features that are of similar scales to those characterising incident waves. The research presented here includes laboratory experiments using synthetic schlieren and PIV to visualise two-dimensional wavefields produced by small amplitude oscillations of cylinders within linear salt-water stratifications. Interactions of wavefields with planar slopes and smoothly varying sinusoidal topography are compared with those with square-wave, sawtooth and pseudo knife-edge profiles, which have discontinuous slopes. Far-field structures of scattered wavefields are compared with linear analytical models. Scatter to high wavenumbers is found to be controlled predominantly by the relative slopes and characterising length scales of the incident wavefield and topography, as well as the shape and aspect ratio of the topographic profile. Wave energy becomes highly focused and the spectra skewed to higher wavenumbers by 'critical' regions, where the topographic slope is comparable with the slope of the incident wave energy vector, and at sharp corners, where topographic slope is not defined. Contrary to linear geometric ray tracing predictions (Longuet-Higgins 1969, J. Fluid Mech. 37), a significant back-scattered field can be achieved in near-critical conditions as well as a forward scattered wavefield in supercritical conditions, where the slope of the boundary is steeper than that of the incident wave. Results suggest that interaction with rough benthic topography could efficiently convert wave energy to higher wavenumbers and promote fluid mixing in such ocean regions.

MAGALHÃES, Frederico Batista. Qualidade da água subsuperficial e de fundo no cultivo de tilápia em tanques-rede na fazenda campo grande (açude Pereira de Miranda, Pentecoste, Ceará). 2013. 69 f. : Dissertação (mestrado) - Universidade Federal do Ceará, Centro de Ciências Agrárias, departamento de Engenharia de Pesca, Fortaleza-CE, 2013
Submitted by Nádja Goes (nmoraissoares@gmail.com) on 2016-07-15T12:09:42Z No. of bitstreams: 1 2013_dis_fbmagalhães.pdf: 1507818 bytes, checksum: 9692206a8b30849b20decf9e956f08ca (MD5)
Approved for entry into archive by Nádja Goes (nmoraissoares@gmail.com) on 2016-07-15T12:10:05Z (GMT) No. of bitstreams: 1 2013_dis_fbmagalhães.pdf: 1507818 bytes, checksum: 9692206a8b30849b20decf9e956f08ca (MD5)
Made available in DSpace on 2016-07-15T12:10:05Z (GMT). No. of bitstreams: 1 2013_dis_fbmagalhães.pdf: 1507818 bytes, checksum: 9692206a8b30849b20decf9e956f08ca (MD5) Previous issue date: 2013
Mankind has an important historical connection with the water especially with Continental Aquatic Ecosystems (CAEs) Worldwide there are about 1386 million km3 of water This value may seem absurdly large almost unimaginable but only a small portion of this amount is freshwater and a smaller portion is still available for consumption by humans This study aimed to determine the effects of tilapia culture in cages held at Fazenda Campo Grande (Weir Pereira de Miranda Pentecost Ceará) the quality of surface and bottom of the cultivation area and systematically monitor the physical-chemical changes nictimerais changes caused by local weather The study was conducted at Aquaculture Campo Grande located in Weir Public Pereira de Miranda located in Petecoste (Ceará - Brazil) Have chosen two stations (PC - Control Point; PTR - Point in Tanks-Net) Were chosen due to location (50 m away) and divide the similar physical characteristics (depth distance from shore etc ) Meteorological data were obtained from FUNCEME and the the Meteorological Station of Universidade Federal do Ceará The campaigns took place every three weeks and began on 24/03/2012 and were finalized on 07/07/2012 Them were collected waters of sub-surface and bottom in two points and at different times (6 12 18 and 24h00min) Even at the site were measured water temperature pH and oxygen fixation occurred by Winckler method In the laboratory were measured electrical conductivity dissolved oxygen total alkalinity total hardness salinity total ammonia nitrogen nitrite iron II and dissolved phosphorus The water clarity was measured with a Secchi disk Each campaign has generated 324 results in water quality total 1944 results at the end of the work In the end it was concluded that the fish farming Campo Grande eutrophication medium so insignificant that the change in water quality is mainly in the bottom water thermal stratification occurred in fish but there was not always a total mixture of the water body waste dispersion was very low keeping the perimeter of the cages and water quality can be organized as follows in order of increasing water quality (from worse to best water): 1 - bottom water of net cages; 2 - bottom water-point control; 3 - sub-surface water of the control points and net cages
A humanidade tem uma importante ligação histórica com a água em especial com os Ecossistemas Aquáticos Continentais (EACs) No mundo existem cerca de 1 386 milhões de km3 de água sendo apenas 2 5% água doce É de extrema importância o conhecimento das variáveis físico-químicas da água para prever de forma antecipada os fenômenos de estratificação e desestratificação térmica Assim podendo evita perdas financeiras em empreendimentos aquícolas O presente trabalho teve como objetivos determinar quais efeitos a tilapicultura em tanques redes realizada na Fazenda Capo Grande (Pentecoste Ceará) exerce sobre os parâmetros da água subsuperficial e de fundo no cultivo e monitorar sistematicamente as alterações físico-químicas nictimerais causadas pelas alterações meteorológicas locais O trabalho foi realizado na Piscicultura Campo Grande localizada no Açude Publico Pereira de Miranda localizado em Pentecoste (Ceará – Brasil) Foram escolhidos dois pontos de coletas com a mesma profundidade e características semelhantes (PC – Ponto controle localizado a 50 m dos tanques-rede; PTR – Ponto nos Tanques-Rede localizado entre os tanques-rede) Os dados meteorológicos foram obtidos através da FUNCEME e da Estação Meteorológica da UFC As campanhas ocorriam a cada 21 dias se iniciaram no dia 24/03/2012 e foram finalizadas no dia 07/07/2012 Coletava-se águas de sub-superfície (0 30 m) e de fundo (3 90 m) nos dois pontos e em horários diferentes (6 12 18 e 24h00min) Ainda no local foram medidos a temperatura da água pH e ocorria a fixação do oxigênio pelo método de Winckler Em laboratório foram medidos a condutividade elétrica oxigênio dissolvido alcalinidade total dureza total salinidade nitrogênio amoniacal total nitrito ferro II e fósforo dissolvido A transparência da água foi medida com um disco de secchi Cada campanha gerou 324 resultados de qualidade de água totalizando 1944 resultados no fim do trabalho Concluiu-se que a Piscicultura Campo Grande eutrofizou o meio de forma insignificante que a alteração da qualidade de água se deu principalmente na água de fundo ocorreram estratificações térmicas na área da piscicultura mas nem sempre ocorreu à mistura total da massa de água a dispersão de resíduos foi muito baixa mantendo-se no perímetro dos tanques-rede e a qualidade da água pode ser organizada da seguinte forma em ordem crescente de qualidade de água (da pior para a melhor água): 1 – água de fundo dos tanques-rede; 2 – água de fundo do ponto-controle; 3 – água subsuperficial dos pontos controle e tanques-rede

La dilution d'un rejet flottant a la surface de la mer est due aux phenomenes de melange et d'etalement gravitaire. A partir de la litterature, on presente des jets de surface gaussien (chu, et lirka 1986), les phenomenes gravitaires (britter et simpson, 1978), et les modelisations locales. Des modeles numeriques permettent de simuler: le comportement global du jet, les effets gravitaires essentiellement sous forme d'un bicouche, ou l'ensemble des phenomenes traites localement. Ces modeles sont analyses. D'importantes campagnes d'investigation sur sites ont ete menees dans le panache de la centrale de gravelines (thermographies aeriennes infrarouge, et de capteurs fixes). Ces campagnes sont analysees. En jusant le jet s'etale librement, en flot il est ecrase contre la digue du port. Aux renverses un melange rapide s'effectue. Le jet presente les caracteristiques gravitaires attendues. Pour le melange: les lois traditionnelles liees a la turbulence de cisaillement sont insuffisantes a la renverse et dans les fronts. Pour la baie de daya, sur la base d'investigations sur site une climatologie generale est proposee qui met en evidence l'influence de la mousson et l'apparition de stratification thermique et saline. L'etude de la dilution d'un rejet est menee en combinant ces elements et les caracteristiques des modeles disponibles. En conclusion, on souligne l'importance d'une approche pragmatique de la modelisation et de la connaissance des conditions de site. De plus, on propose des domaines de recherche, en particulier sur les lois de melange et de turbulence

Orientador: Roberto Fioravanti Carelli Fontes
Resumo: Estuários são ambientes aquáticos de transição entre o continente e o oceano com características únicas, ecológica e economicamente importantes. São condicionados por diversas forçantes naturais e compartilham contribuições terrestres e marinhas. Os principais métodos para estudo hidrodinâmico desses ambientes baseiam-se na análise dos processos de advecção e de mistura das massas de água, gerados pela dinâmica das marés e das descargas dos rios. O presente estudo visa a caracterização hidrodinâmica do estuário do rio Guaratuba (Bertioga, SP) durante as marés de sizígia e de quadratura, a partir de levantamentos hidrográficos realizados com ADCP e CTD e o desenvolvimento de um modelo hidrodinâmico computacional capaz de explicar e simular os processos oceanográficos deste estuário. Os resultados apontaram que, tanto a maré quanto a descarga fluvial têm a capacidade de alterar as vazões e os padrões de salinidade e temperatura no estuário. Em condições de precipitação médias ou na ausência de precipitações, a maré é a forçante dominante do sistema. Durante os períodos de sizígia ocorrem o aumento da turbulência e da mistura vertical. Nas quadraturas, quando as velocidades de corrente são menores, a estratificação vertical é mais estável, e a água salina incursiona até pontos mais internos do estuário. Precipitações na sub-bacia tem relação direta e imediata com o aumento da vazão, afetando a dinâmica e intensificando a estratificação vertical do estuário. O estuário do rio Gua... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Estuaries are transitional aquatic environments, with unique characteristics, ecologically and economically important. They are conditioned by several natural forcings and share land and marine contributions. The main methods to study these environments are based on the analysis of the water masses advection and mixing processes, that are generated by tides and river discharges. The purposes of this study are the hydrodynamic characterization of the Guaratuba’s estuary (Bertioga, SP) during spring and neap tides, based on ADCP and CTD hydrographic surveys, and the development of a computational hydrodynamic model using Delft-3D software, that helps to explain and simulate the main estuarine oceanographic processes. We observed that both, tide and river discharges, have the capacity to alter water flow, as well as salinity and temperature patterns in the estuary. Under mean precipitation conditions or in its absence, tide forces dominate the system. During the spring tide floods, turbulence and vertical mixing increase. During the neap tide floods, when current speed decreases, vertical stratification remains more stable, and saline water penetrates more along the upper estuary. Precipitation episodes in the sub-basin are direct and immediate related to water flow increase, and affect currents dynamics intensifying vertical stratification in the estuary. The Guaratuba estuary is classified as type A, B or D; depending on tidal and river flow conditions. The models we generated... (Complete abstract click electronic access below)
Mestre

The goal is to design a storage tank to the heat pumps air to water. The first part describes how a heat pump works and why it is advantageous to use the tank. Another section focuses on ways to accumulation of heat. Established a program that simulates the behavior of the heat pump system with storage tank, described how this program works and is designed tank size for a given heat pump. The last chapters deal with the calculation of minimum area of heat flow exchanger and the proposal inlet valve for improving the thermal stratification of the tank.

Radiale Diffusoren beeinflussen signifikant die Qualität der thermischen Schichtung in Warmwasserspeichern. Um die Effizienz der Energiespeicherung zu verbessern, ist das Verständnis des komplexen Strömungsverhaltens notwendig. Diese Arbeit liefert Grundlagen zur Beschreibung der auftretenden Effekte und stellt ein geeignetes CFD-Simulationsmodell vor. Als Untersuchungsobjekt dient eine neuartige Speicherkonstruktion, wobei der Radialdiffusor direkt an einer schwimmenden Decke montiert ist. Vorteile dieser Anordnung werden aufgezeigt, die auftretenden Strömungseffekte beschrieben sowie der Einfluss verschiedener Beladergeometrien auf die thermische Schichtung untersucht. Für das Entladen bis 98 °C bei Atmosphärendruck wurde ein strömungsoptimierter Freiformdiffusor entwickelt, um Kavitation beim Ansaugen zu vermeiden. Die Untersuchungen zeigen außerdem, dass bei der Beladung über dem Umfang des Radialdiffusors ein stark asymmetrisches und einseitig gerichtetes Ausströmen auftreten kann. Gegenmaßnahmen in Form von Leit- und Lochblechen stellen ein nahezu symmetrisches Ausströmen wieder her und verbessern damit die Schichtungsqualität. Neben umfangreichen numerischen Studien mit RANS und LES fanden zahlreiche Experimente im Labor und an einem 100 m³-Speicher statt.
Radial diffusers have a significant influence on the quality of thermal stratification in hot water storage tanks. In order to improve the efficiency of energy storage, it is necessary to understand the complex flow behaviour. This thesis provides a basis for describing the effects and introduces a CFD simulation model. An innovative storage tank construction is used as the object of investigation, whereby the radial diffuser is mounted directly to a floating ceiling. Advantages of this arrangement are shown, flow effects are described and the influence of different loader geometries on the thermal stratification is investigated. For discharging up to 98 °C at atmospheric pressure, a flow-optimized free-form diffuser was developed to avoid cavitation inside the loading device. The tests also show that a highly asymmetrical and unidirectional flow over the circumference of the radial diffuser can occur during loading. Thanks to countermeasures like baffles and perforated plates, an almost symmetrical outflow can be restored and the stratification quality improved. In addition to numerical studies with RANS and LES, numerous experiments in the laboratory and at a 100m3 store were performed.

This research presents an analysis of thermal stratification in the reactor cold leg of the Advanced Plant Experiment-Combustion Engineering (APEX-CE). This phenomenon may be a precursor leading to a Pressurized Thermal Shock (PTS) event in a nuclear power plant. This work was performed in support of the U.S. Nuclear Regulatory Commission's (USNRC) re-evaluation of its PTS regulations. Using the APEX-CE test facility, thermal stratification was observed for injection flow rates ranging from 30% to 100% and natural circulation flow rates that were generated by core decay powers ranging from 1.5% to 4%, both relative to the scaled Palisades values. A theoretical model was derived to estimate the hot stream entrainment that occurs during cold leg thermal stratification. This model was applied to the Separate Effects Transparent Loop (SETL) facility, a scaled cold leg/downcomer configuration of the APEX-CE plant. The model predictions were in reasonable agreement with the High Pressure Injection (HPI) fluid entrainment data from the Purdue ½ scale facility. The same model was then used to estimate HPI entrainment in SETL. The results proved to be very consistent. Finally, data for the onset of loop seal spillover was obtained using SETL and APEX-CE. A useful flow map, characterizing the onset condition, was generated.
Graduation date: 2002

Research Doctorate - Doctor of Philosophy (PhD)
Phytoplankton are a natural component of aquatic ecosystems; however, when present in high cell densities as “blooms”, they can pose a significant potential threat to human and ecological health. These phytoplankton blooms are often composed of microorganisms with the potential to produce toxins (cyanobacteria) that can cause adverse health effects in humans and animals through the contamination of waterways used for recreational purposes and as drinking water supplies. There is general agreement that nutrient enrichment of water bodies with nitrogen (N) and phosphorus (P) is the main reason for bloom formation, and that nutrients are typically introduced by inflows to a waterbody. However, sediments can also play an important role in releasing nutrients to water bodies. This can occur by reactivation of sediments under depleted dissolved oxygen levels during thermal stratification. Thus, in order to reduce the nutrient enrichment of aquatic systems, it is important to target both the external and internal nutrient loadings in managing a water reservoir. However, it is also essential to investigate the environmental factors other than nutrients, such as water clarity, water temperature and dissolved oxygen concentration that may influence the formation of algal blooms. This holistic approach has been applied in this study to investigate variations in water quality and the abundance of cyanobacteria in Grahamstown Reservoir, the principal drinking water reservoir of Newcastle and the lower Hunter Region in New South Wales, Australia. Multivariate data analysis methods based on Principal Component Analysis (PCA) and Multivariate Curve Resolution Alternating Least Squares (MCR-ALS) were used in the identification of important water quality variables, as well as the main sources or factors which can influence water quality within Grahamstown Reservoir. PCA and MCR-ALS further were applied to investigate seasonal changes in the abundance and species composition of cyanobacteria in the reservoir in response to changes in environmental factors. Moreover, the seasonal thermal stratification pattern and its role in the formation of algal blooms was also investigated in Grahamstown Reservoir. A part of this study was also focused on an overview of the issues relating to taste and odour problems in Grahamstown Reservoir. This part of the project was aimed at assessing the occurrence of cyanobacteria abundance to better understand their relative potential to produce significant tastes and odours which affect water quality. The water quality data examined in this study has been collected from different sites within Grahamstown Reservoir by routine sampling by Hunter Water Corporation (HWC) who manage the drinking water storage. The expected outcome of this study is the identification of the factors and sources of contaminants which could influence the water quality of Grahamstown Reservoir and thereby further inform the management strategies needed to prevent and minimise the risk of algal blooms in the future. Also, determination of the environmental factors other than nutrients that may influence the formation of algal blooms.

Research Doctorate - Doctor of Philosophy (PhD)
Phytoplankton are a natural component of aquatic ecosystems; however, when present in high cell densities as “blooms”, they can pose a significant potential threat to human and ecological health. These phytoplankton blooms are often composed of microorganisms with the potential to produce toxins (cyanobacteria) that can cause adverse health effects in humans and animals through the contamination of waterways used for recreational purposes and as drinking water supplies. There is general agreement that nutrient enrichment of water bodies with nitrogen (N) and phosphorus (P) is the main reason for bloom formation, and that nutrients are typically introduced by inflows to a waterbody. However, sediments can also play an important role in releasing nutrients to water bodies. This can occur by reactivation of sediments under depleted dissolved oxygen levels during thermal stratification. Thus, in order to reduce the nutrient enrichment of aquatic systems, it is important to target both the external and internal nutrient loadings in managing a water reservoir. However, it is also essential to investigate the environmental factors other than nutrients, such as water clarity, water temperature and dissolved oxygen concentration that may influence the formation of algal blooms. This holistic approach has been applied in this study to investigate variations in water quality and the abundance of cyanobacteria in Grahamstown Reservoir, the principal drinking water reservoir of Newcastle and the lower Hunter Region in New South Wales, Australia. Multivariate data analysis methods based on Principal Component Analysis (PCA) and Multivariate Curve Resolution Alternating Least Squares (MCR-ALS) were used in the identification of important water quality variables, as well as the main sources or factors which can influence water quality within Grahamstown Reservoir. PCA and MCR-ALS further were applied to investigate seasonal changes in the abundance and species composition of cyanobacteria in the reservoir in response to changes in environmental factors. Moreover, the seasonal thermal stratification pattern and its role in the formation of algal blooms was also investigated in Grahamstown Reservoir. A part of this study was also focused on an overview of the issues relating to taste and odour problems in Grahamstown Reservoir. This part of the project was aimed at assessing the occurrence of cyanobacteria abundance to better understand their relative potential to produce significant tastes and odours which affect water quality. The water quality data examined in this study has been collected from different sites within Grahamstown Reservoir by routine sampling by Hunter Water Corporation (HWC) who manage the drinking water storage. The expected outcome of this study is the identification of the factors and sources of contaminants which could influence the water quality of Grahamstown Reservoir and thereby further inform the management strategies needed to prevent and minimise the risk of algal blooms in the future. Also, determination of the environmental factors other than nutrients that may influence the formation of algal blooms.

Solar domestic hot water (SDHW) systems collect energy with a solar collector, transfer the energy to the water through a heat exchanger, and store it in a storage tank. The water in the tank should be thermally stratified to the highest possible degree to maximize system efficiency because a stratified tank has higher availability than a mixed tank temperature. The objective of this research is to develop a manifold that will enhance thermal stratification in the SDHW tank. In this work a new immersion shell-and-coil heat exchanger with a perforated manifold that extends from the heat exchanger to the top of the tank was used to enhance the thermal stratification. The purpose of the perforated manifold is to deliver the water heated by the heat exchanger to the tank at the level where the temperature of the water in the tank matches the temperature of the heated water, thereby enhancing stratification. The effectiveness of the perforated manifold was determined experimentally. An experimental set-up was designed and constructed. The experimental results were analyzed for each manifold design then compared to determine the most effective manifold. The experimental work included testing and comparing different manifold designs. To simulate an actual system, experiments were conducted on three initial tank conditions, namely cold, hot, and mixed tank conditions. The thermal performance of the system in terms of tank availability and entropy, maximum tank temperature, and thermal stratification were studied. A method to determine and design a perforated manifold that works with the standard Canadian SDHW system was established and evaluated experimentally. An availability analysis approach was developed to evaluate the thermal performance of manifolds, which have been operated at different times of the year. Theoretically, gradually increasing the diameter of the holes in the manifold from the bottom into the top should reduce the unwanted flow of cold water from the bottom of the tank to the manifold and enhance the thermal performance of the manifold. However, the experimental did not confirm this.

Tese de doutoramento em Engenharia Civil
Eutrophication is a serious environmental problem in lakes and reservoirs worldwide. The eutrophic Alqueva reservoir (Portugal) is the largest western European reservoir and constitutes a vital regional water resource. The river Guadiana, which is the main tributary to the Alqueva reservoir, imports large nutrient loads leading to eutrophication being an issue in this waterbody. But despite its importance and problems, few scientific studies concerning the Alqueva exist. This work aims at contributing to foster the understanding of water ecology in the Alqueva reservoir through the use of data analysis techniques and numerical modelling. The results contained herein can be used to assist management decisions in this waterbody and the modelling effort can be used to obtain forecasts in this and other reservoirs and improve understanding of ecological behavior there. Data analysis methods, namely time series analysis, were applied to monitoring data collected between 2003-2009 at several locations and depths in the Alqueva reservoir in order to infer possible spatial and temporal patterns. The monitoring data comprised climatology, hydrology and water quality data from different sources. Data analysis showed that the Alqueva behavior presents high interannual variability. This is mainly a consequence of the high variability of precipitation, nutrient loads and Guadiana hydrological regimen. It was found that the system is P-limited and that nutrients input is mostly dependent on the main tributary input loads. Therefore management schemes aimed at improving the trophic level in the Alqueva should focus on reducing phosphorus in the Guadiana inflow. Numerical modelling main goals were to develop and apply tools to simulate the main ecological traits in the Alqueva reservoir. A new numerical model to simulate eutrophication processes in lakes and reservoirs based on a hybrid deterministic-stochastic approach was developed. A plain methodology to estimate nutrient loads in a basin was also developed. These tools were used together with the finite element based hydrodynamic model RMA-10 to perform simulations of currents, thermal structure and eutrophication in the Alqueva reservoir. The models were successfully calibrated and validated in both two-dimensional and three-dimensional versions. Model performance was assessed by comparing simulation results with in situ measured data. It was found that the models reproduced Alqueva thermal structure quite accurately and eutrophication related trends reasonably well. The performance of the eutrophication tool was constrained by the availability and quality of input and forcing data. It was shown that the particular geomorphological and hydrological characteristics of the reservoir together with local climate features are responsible for the existence of two distinct ecological regions within the reservoir whose boundary can be placed at a transect south of monitoring station 3: - The upper part of the reservoir is a shallow channel like region with riverine characteristics that is interrupted by a few scattered deeper pools. This area receives the major nutrients input and is eutrophic. Hydrodynamic in this area is governed by hydraulically induced currents from the Guadiana. - The lower part of the reservoir is a deep lacustrine area that presents stable thermal and oxygen stratification in summer (April – October). In this region, wind induced currents and thermal stratification are the dominant hydrodynamic traits. Wind is dominant over hydraulic flow during all year and affects mostly the surface circulation. Model results indicate that the velocities in the reservoir are always smaller than 0.25 m/s, with the higher values occurring in the upper reservoir area. The Alqueva was found to present a monomictic behavior with a seasonal summer stratification that is responsible for generating anoxic bottom waters during dry season. An autumnal overturn leads to a fully mixed water column in winter season. Model findings, corroborated by data, indicate that phytoplankton in the Alqueva peaks in spring and in autumn with productivity in the upper reservoir area presenting values much higher than in the lower part. Dry season ecology seems to be ruled by stratification while wet season ecology main driving force appears to be the nutrients load through the main tributary. The Alqueva was build to boost economic development in the region and provide irrigation water for agriculture activities. It can be inferred from the results of the present work that the major problem it may face is the impacts of the poor water quality coming from the Guadiana. The Guadiana river carries wastewater with a high level of nutrients from a large Spanish population, from industries and from agriculture activities. The development of effective water quality management in this reservoir should therefore focus on nutrient containment strategies for the Guadiana river inflow.
A eutrofização constitui um sério problema ambiental em lagos e albufeiras. A albufeira de Alqueva (Portugal) é a maior albufeira da Europa ocidental e constitui um importante recurso aquático regional. O principal afluente de Alqueva, o rio Guadiana, introduz elevadas cargas de nutrientes na albufeira fazendo com que a eutrofização seja motivo de preocupação nesta albufeira. Apesar da sua importância e problemas, existem poucos estudos científicos sobre a albufeira de Alqueva. Este trabalho tem como objectivo contribuir para o conhecimento e compreensão da ecologia aquática na albufeira de Alqueva através do uso de análise de dados e modelação matemática. Os resultados obtidos podem ser utilizados na tomada de decisões de gestão nesta albufeira e o trabalho de modelação pode ser utilizado para efectuar previsões nesta ou noutras albufeiras ou lagos. Foram aplicados métodos de análise de dados, nomeadamente métodos de análise de séries temporais, a dados de campanhas de monitorização recolhidos no período 2003-2009 em diferentes pontos da albufeira de Alqueva para inferir da existência de padrões espaciais e temporais. Os dados de monitorização são oriundos de diferentes fontes e abrangem climatologia, hidrologia e qualidade da água A análise de dados permitiu concluir que a ecologia do Alqueva tem uma elevada variabilidade interanual que é consequência da elevada variabilidade da precipitação, cargas de nutrientes e regime hidrológico. Concluiu-se que o nutriente limitante é o fósforo e que a entrada de nutrientes no sistema depende sobretudo das cargas que entram pelo afluente principal. Donde resulta que uma gestão eficiente da melhoria do estado trófico da albufeira deve centrar-se na redução do fósforo nas afluências do Guadiana. Os principais objectivos da modelação foram desenvolver e aplicar ferramentas para simular as principais características ecológicas da albufeira de Alqueva. Desenvolveu-se um novo modelo matemático para simular a eutrofização em lagos e albufeiras baseado numa abordagem híbrida determinística-estocástica. Desenvolveu-se também uma metodologia simples para estimar cargas de nutrientes em bacias hidrográficas. Estes instrumentos foram utilizados em conjunto com o modelo hidrodinâmico RMA10, baseado no método dos elementos finitos, para simular correntes, estrutura térmica e eutrofização na albufeira de Alqueva. Os modelos foram calibrados e validados com sucesso nas versões tridimensional e bidimensional integrada lateralmente. O desempenho dos modelos foi avaliado por comparação entre os resultados de simulações e medidas experimentais realizadas in situ. Verificou-se que os modelos reproduzem com grande exactidão a estrutura térmica da albugeira de Alqueva e razoavelmente bem as variações relacionadas com a eutrofização. O desempenho do modelo de eutrofização foi condicionado pela disponibilidade e qualidade dos dados de entrada e de forçamento. Mostrou-se que as características geomorfológicas e hidrológicas particulares da albufeira, em conjunto com características climáticas locais, são responsáveis pela existência de duas zonas ecológicas distintas na albufeira, cuja fronteira se localiza a sul da estação de amostragem 3: - A parte superior da albufeira é uma região de leito linear com águas pouco profundas, interrompida a espaços por lagoas mais profundas, que tem características fluviais. Esta zona é muito eutrófica e por ela entram a maior parte dos nutrientes do sistema. A hidrodinâmica nesta área é governada por correntes induzidas pelo fluxo do Guadiana. - A parte inferior da albufeira é uma região lacustre profunda que apresenta estratificações térmica e de oxigénio estáveis durante o verão (Abril - Outubro). Nesta zona as características hidrodinâmicas dominantes são as correntes induzidas pelo vento e a estratificação térmica. O vento é dominante sobre o fluxo hidráulico durante todo o ano e afecta sobretudo a circulação à superfície. Os resultados da modelação indicam que as velocidades na albufeira são sempre inferiores a 0.25 m/s, com os maiores valores a ocorrer na parte superior da albufeira. Concluiu-se que a albufeira de Alqueva apresenta um comportamento monomíctico com uma estratificação sazonal de verão que é responsável pela geração de camadas de água anóxica no fundo da albufeira durante a estação seca. A circulação convectiva outonal dá origem a uma coluna de água completamente misturada na estação do inverno. Os resultados de modelação, corroborados por dados de campo, indicam que o fitoplâncton no Alqueva apresenta picos primaveris e outonais, com a produtividade na parte superior da albufeira a apresentar sempre valores muito superiores à da parte inferior. A ecologia da estação seca parece ser governada pela estratificação ao passo que a força motriz da ecologia da estação húmida aparenta ser a carga de nutrientes que entra através do afluente principal. A barragem de Alqueva foi construída para fomentar o desenvolvimento económico regional e fornecer água de irrigação para actividades agrícolas. Dos resultados obtidos neste trabalho pode-se concluir que o maior problema com que a albufeira se depara é os impactos da água de baixa qualidade que é trazida pelo rio Guadiana. O Guadiana transporta efluentes com um elevado nível de nutrientes provenientes de uma vasta população espanhola, de indústrias e de actividades agrícolas. Consequentemente, o desenvolvimento de uma gestão de qualidade da água eficaz nesta albufeira deve centrar-se em estratégias de remediação/contenção do fósforo trazido pelo Guadiana.

abstract: C.C. Cragin Reservoir’s location in the Coconino National Forest, Arizona makes it prone to wild fire. This study focused on the potential impacts of such a wild fire on the reservoir’s annual thermal stratification cycle impacts and water quality. The annual thermal stratification cycle impacted the reservoir’s water quality by increasing hypolimnion concentrations of magnesium, iron, turbidity, and specific ultraviolet absorbance (SUVA) values, as well as resulting in the hypolimnion having decreased dissolved oxygen concentrations during stratified months. The scarification process did not affect the dissolved organic carbon (DOC) concentrations in the reservoir or the total/dissolved nitrogen and phosphorous concentrations. Some general water quality trends that emerged were that phosphorous was the limiting nutrient, secchi disk depth and chlorophyll a concentration are inversely related, and no metals were found to be in concentrations that would violate an EPA drinking water maximum contaminant level (MCL). A carbon mass model was developed and parameterized using DOC measurements, and then using historic reservoir storage and weather data, the model simulated DOC concentrations in the reservoir following four hypothetical wild fire events. The model simulated varying initial reservoir storage volumes, initial flush volumes, and flush DOC concentrations, resulting in reservoir DOC concentrations varying from 17.41 mg/L to 8.82 mg/L.
Dissertation/Thesis
Masters Thesis Civil, Environmental and Sustainable Engineering 2018

碩士
國立中山大學
海洋科學系研究所
104
The North Pacific Intermediate Water (NPIW) plays an important role on driving the global climate change, which can control the heat transportation from low to high latitude. However, the long-term changes of NPIW are still rare understood. In this study, by using Unsaturated Alkenone Index (U_37^(k^'' )) and foraminiferal Mg/Ca to represent the different temperature of water depths, the historical hydrography evolution of water profile can be reconstructed. Therefore, we can investigate the relationship between climate events and the circulation changes in northwestern Pacific.As the result, using ΔT to reconstruct the mixed layer change is applicable in Shatsky Rise, and we suggest to use other species which have small estimating errors, in order to get more reliability results on western Pacific paleoceanographic studies. The U_37^(k^'' ) temperatures reveal a regional cold period during MIS 5e in Shatsky Rise, which is probably not caused by the movement of Subarctic Front, but the violently fluctuation of the Kuroshio Extension. The result ofΔTU-N and ΔTU-G show thatΔTU-G are more sensitive than ΔTU-N, in which that ΔTU-N is more truly represent the change of NPIW. Reconstructed ΔTU-N and ΔTU-G curves indicate that MIS 2 is warmer than MIS6. Otherwise, ventilation age data confirmed that the mixed layer is deeper during the late MIS 3. In MIS 5, both ΔTU-N and ΔTU-G records illustrate the increased mixed layer depth during warm periods, but decreased in cold periods. Therefore, the stratification is weakened which the circulation of NPIW can be strengthen during the cold periods.

This thesis examines geomorphic processes that impact thermal stratification within floodplain lakes. Previously, thermal stratification was not thought prevalent in these numerous small water bodies, despite being found in small reservoirs. Thermal stratification leads to long term anoxia in the bottom waters and the release of metals and nutrients from the sediments. This can result in water quality problems such as algal blooms (including potentially toxic cyanobacteria), loss of fish habitat and deterioration of wetland habitat. Four floodplain lakes of the Macdonald River Valley NSW were profiled and tested over 3?? years to assess to what extent, under what conditions, and with what chemical and physical effects, they thermally stratified and destratified. The morphometry, bed facies, vegetation, hydrology and local weather patterns for each lake were also investigated. Physical and chemical analyses found elevated nutrients in all four lakes and higher concentrations of total phosphorous and total nitrogen in the bottom waters. These results were not dependant on stable thermal stratification and long-term anoxia in the bottom waters. Inflow samples had much higher concentrations of nutrients than the lake samples, so the catchment is the likely source. Samples were analysed for phytoplankton and significant populations of potentially toxic cyanobacteria were present. Stratification depended upon whether the lake was "sheltered" from wind stirring or from incident radiation, either topographically by steep slopes surrounding the lakes, or by submerged and emergent vegetation. Aquatic vegetation limits the amount of transfer of turbulent kinetic energy from wind shear and the amount of incident radiation received. At one lake, sheltered areas reached temperatures much higher than less sheltered areas. Topographic sheltering can make a difference of up to three degrees Celsius across the lake surface. Destratification depended on wind speed, wind direction and orientation of the lake to the dominant wind direction. An extension to the classification of fluvial lakes (from Timms 1992) is presented, with further subdivisions to describe the lakes as "sheltered" or "open" and the type of sheltering (vegetation or topography) present.