Dissertations / Theses on the topic 'Boundary heat flux'

The thermal boundary condition to a fire exposed surface was quantified with a hybrid heat flux gage. Methods were developed to determine the net heat flux through the gage, incident heat flux, cold surface heat flux, convective heat transfer coefficient, adiabatic surface temperature, and the separated components of radiative and convective heat flux. Experiments were performed in a cone calorimeter with the hybrid gage flush mounted into UNIFRAX Duraboard LD ceramic board. The results were then compared to results obtained with a Schmidt-Boelter gage and a plate thermometer. The hybrid heat flux gage predicted a cold surface heat flux within 5% of cold surface heat fluxes measured with a Schmidt-Boelter gage. Adiabatic surface temperature measurements compared well with the plate thermometer measurements at steady state. Hybrid gage measurements were performed on flat plate samples of Aluminum 5083, Marinite P, and UNIFRAX Duraboard LD ceramic board. The gage and sample assemblies were exposed to mixed-mode heat transfer conditions in a cone calorimeter. Temperature measurements were performed at the top, center, bottom surfaces of the marinite and ceramic board samples. A single midpoint temperature was performed on the aluminum. Boundary condition details obtained with the hybrid gage were then input to the commercial finite element analysis package Abaqus. Abaqus was used to create the flat plate geometries of the sample and variable temperature dependent material properties were used for each material. Measured temperatures were then compared to the model predicted temperatures with good results. Hybrid gage measurements were verified using a new experimental apparatus. The apparatus consisted of an impinging jet assembly, a tungsten lamp, and a gage holster assembly. The impinging jet was used to expose the gage to isolated convection and the lamp was used to expose the gage to isolated radiation. The gage holster assembly was used to water cool the gage when desired. Measurements performed with the gage water cooled in isolated convection allowed for the convective heat transfer coefficient to be determined. Two methods were developed to determine the convective heat transfer coefficient in mixed-mode heat transfer conditions. These methods were then verified by comparison to the isolated heat transfer coefficient. Similarly, the incident radiation was isolated by water cooling the gage while only the lamp was on. The components of heat flux were then separated for mixed-mode comparisons and were verified against this isolated radiation. The hybrid gage predicted convective heat transfer coefficients within 10% of the isolated heat transfer coefficient and incident heat fluxes within 11% of the isolated radiation.
Master of Science

The surface character of a suburban area is far from the uniform, smooth and flat planes over which current surface-layer theory is valid and where vertical eddy-fluxes can be assumed to be almost constant horizontally and vertically. The complexity of the surface introduces considerable variability into the atmosphere at small spatial scales. This variability is partly reduced and spatially-averaged by turbulent mixing but still leaves the concerns about the spatial representativeness of sensible heat flux measurements over a suburban area. The spatial scales of sensible heat flux variability are discussed in terms of the distribution of surface temperature and roughness elements. It is shown that : (1) an eddy-correlation measurement can be considered spatially representative, if its surface zone of influence (source area) is large enough to include a spatially representative sample of surface temperature and roughness elements. (2) a quantitative measure of spatial representativeness can be estimated by use of the two-dimensional Fourier transform of the surface temperature and roughness element distributions (i.e. by the normalized integrated variance spectrum). (3) the source area of an eddy correlation measurement may be evaluated by a numerical model based on a probability density function plume diffusion model. The source area model developed herein can also be used to estimate the relative influence of specific surface sources or sinks upon an eddy-flux measurement in the surface layer. These concepts are tested in a suburban residential area in Vancouver, B.C., Canada. Remotely sensed surface temperatures and a digitized roughness element inventory are used as data-bases for the Fourier transforms to develop representativeness criteria for eddy-flux measurements. A set of sensible heat flux measurements at six sites and the corresponding source area calculations are used to formulate recommendations for the objective evaluation of the spatial representativeness of sensible heat flux measurements over a suburban area. The validity of the suggested evaluation methods is confirmed by the observations. Internal boundary layer growth, estimated by the source area model, compares well with existing work. Some consequences of complex surfaces on the surface layer structure are briefly discussed.
Arts, Faculty of
Geography, Department of
Graduate

Thesis (M.S. in Mechanical Engineering) Naval Postgraduate School, December 1996.
"December 1996." Thesis advisor(s): Matthew Kelleher, Pat E. Phelan. Includes bibliographical references (p. 73-75). Also available online.

Oceans cover about 70% of the earth’s surface. They are the largest source of the atmospheric water vapour and act as enormous heat reservoirs. Thus in order to predict the future weather and climate it is of great importance to understand the processes governing the exchange of water vapour and heat between the ocean and atmosphere. This exchange is to a large extent mediated by turbulent eddies. Current numerical climate and weather forecast models are unable to resolve the turbulence, which means that the turbulent exchange needs to be simplified by using parameterizations.

Tower based measurements at the Östergarnsholm Island in the Baltic Sea have been used to study the air-sea turbulent exchange of latent and sensible heat and the heat flux parameterizations. Although the measurements are made at an island, data obtained at this site is shown to represent open ocean conditions during most situations for winds coming from the east-south sector. It is found that during conditions with small air-sea temperature differences and wind speeds above 10 m s^-1, the structure of the turbulence is re-organized. Drier and colder air from aloft is transported to the surface by detached eddies, which considerably enhance the turbulent heat fluxes. The fluxes where observed to be much larger than predicted by current state-of-the-art parameterizations. The turbulence regime during these conditions is termed the Unstable Very Close to Neutral Regime, the UVCN-regime.

The global increase of the latent and sensible heat fluxes due to the UVCN-regime is calculated to 2.4 W m^-2 and 0.8 W m^-2 respectively. This is comparable to the current increase of the radiative forcing due to anthropogenic emissions of greenhouse gases, reported in Intergovernmental Panel on Climate Change fourth assessment report (IPCC AR4). Thus the UVCN-effect could have a significant influence when predicting the future weather and climate.

Knowledge of the turbulent fluxes at the sea surface is important for understanding the interaction between atmosphere and ocean. With better knowledge, improvements in the estimation of the heat exchange coefficients can be made and hence models are able to predict the weather and future climate with higher accuracy.

The exchange coefficients of latent and sensible heat during stable stratification vary in the literature. Therefore it is necessary to investigate the processes influencing the air-sea exchange of water vapour and heat in order to estimate these values. With measurements from a tower and a directional waverider buoy at the site Östergarnsholm in the Baltic Sea, data used in this study have been sampled from the years 2005-2007. This site represents open-ocean conditions during most situations when the wind comes from the south-east sector. The neutral exchange coefficients, CEN and CHN, have been calculated along with the non-dimensional profile functions for temperature and wind to study the dependence of stability and other parameters of relevance.

It was found that CEN increased slightly with wind speed and reached a mean value of approximately 1.45×10-3. The highest values of CEN were observed during near neutral conditions and low wave ages. CHN attained a mean value of approximately 0.77×10-3 and did not show any relation to wind speed or to wave age. No significant dependence with wind or wave direction could be shown for either CEN or CHN in the sector 80-220°. The stability correction, performed to reduce the dependence on stratification for CEN and CHN, was well performed for stabilities higher than 0.15. The stability is represented by a relationship between the height and the Obukhov-length (z/L).

Validity of the non-dimensional profile functions for temperature and wind showed that, for smaller stabilities, these functions gave higher values than the corresponding functions recommended by Högström (1996). The profile funtions for temperature was shown to have a larger scatter while the profile functions for wind was less scattered and deviated more from the functions given by Högström

Kunskap om turbulenta flöden i det marina gränsskiktet är viktigt för att förstå växelverkan mellan atmosfär och hav. Med bättre kunskap kan förbättringar i bestämningen av utbyteskoefficienterna för latent och sensibelt värme erhållas. Det medför att modeller kan prognostisera väder och framtida klimat med högre noggrannhet.

Utbyteskoefficienterna för latent och sensibelt värme har för stabil skiktning olika värden i litteraturen. Detta gör det nödvändigt att undersöka de processer som påverkar utbytet av vattenånga och värme mellan luft och hav för att kunna bestämma dessa värden. Data som har använts i den här studien insamlades mellan år 2005 och 2007 från en boj och ett torn vid mätplatsen Östergarnsholm i Baltiska havet. För det flesta situationer, när vinden blåser från syd-ost, representerar mätplatsen ett förhållande likvärdigt det över öppet hav. De neutrala utbyteskoefficienterna, CEN och CHN, och de dimensionslösa profilfunktionera för temperatur och vind, och , har beräknats för att studera beroendet av stabilitet samt andra relevanta parametrar.

Beräkningarna visade att CEN ökade något med vindhastighet och hamnade på ett medelvärde av ungefär 1.45×10-3. De högsta värdena på CEN observerades vid nära neutrala förhållanden och låga vågåldrar. CHN uppmättes till att ha ett medelvärde på ungefär 0.77×10-3 och uppvisade inget beroende med vindhastighet eller vågålder. Inget märkbart beroende med vind- eller vågriktning kunde visas för CEN eller CHN i sektorn 80-220°. Stabilitetskorrektionen, utförd för att reducera beroendet av atmosfärens skiktning för CEN och CHN, var bra för stabiliteter högre än 0.15. Stabiliteten representeras av förhållandet mellan höjden och Obukhov-längden (z/L).

Utvärdering av de dimensionslösa funktionerna för temperatur och vind visade att dessa funktioner, för små stabiliteter, gav högre värden än motsvarande funktioner som rekommenderas av Högström (1996). Värdena på profilfunktionerna för temperatur hade större spridning än värdena på profilfunktionerna för vind och avvek mer från funktionerna givna av Högström.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2013.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis. Pages [228-229] blank.
Includes bibliographical references.
Progress towards a viable fusion reactor will require comprehensive understanding of boundary plasma physics. Knowledge in this area has been growing, yet there are critical gaps. Measurements of the sheath heat flux transmission coefficient-a fundamental physical quantity whose theoretical value is ~ 7-have varied from 2 to 20. Values below 5 are physically impossible and have challenged the understanding of this very basic theory. In addition, measurements of ion temperature are sparse and ion energy transport is poorly understood. To this end a set of new diagnostics, including a surface thermocouple, ion sensitive probe, and retarding field analyzer, have been developed that can tolerate the extreme heat fluxes in the Alcator C-Mod boundary plasma. These probes are used to asses issues of heat flux and ion energy transport. Systematic studies with these new tools reveal the following: A comparison of surface thermocouples and Langmuir probes confirms standard sheath heat flux theory in a tokamak for the first time. The measurement of unphysically low sheath heat flux transmission coefficients and an anomalous increase in measured divertor pressure by Langmuir probes, which is also unphysical, are found the be linked. Plasma-neutral simulations indicate that these artifacts are due to the Langmuir probe bias modifying the local plasma. Important space charge limits to measurements with ion sensitive probes are found experimentally and explored in depth with a 1D kinetic simulation. These results clarify the plasma conditions under which an ion sensitive probe may be used to measure ion temperature and/or plasma potential. The retarding field analyzer is demonstrated to be a viable ion temperature diagnostic up to the last closed flux surface in C-Mod. A ₁D fluid simulations is built to interpret edge ion heat transport. At high collisionality-where the fluid approximations are valid: the simulation reproduces the measured edge ion-to-electron temperature ratio (~ 2). However, at low collisionality-where fluid approximation is not valid-the simulation is not able to reproduce the experimental temperature ratio (~ 4). The addition of kinetic heat flux limiters can bring the simulated ratio into agreement with measurements. The value of heat flux limiter is found to be consistent with that expected from kinetic theory.
by Daniel Frederic Brunner.
Ph. D.

In this study the flux attenuation due to sensor displacement has been investigated over sea using an extensive set of data from the "Ocean Horizontal Array Turbulence Study". All previous investigations of the flux attenuation have been performed over land.

A function developed for correcting fluxes in the homogenous surface layer was compared to measured flux attenuation. This investigation revealed the possibility to find new functions describing the flux attenuation when measurements are carried out over sea. From the measured flux attenuation studied here a change in the form of correction functions was required to improve the estimated flux loss. The most significant difference found in this report compared to the previous landbased study Horst (2006) is for stable conditions, where significantly less flux loss is found over sea. Two new functions describing the attenuation due to sensor displacement over sea have been constructed.

One of these expressions has a discontinuity at z/L = 0. This is supported by measured flux attenuation. A reasonable interpretation is; however, that this discontinuity is caused by two separate turbulence regimes near neutrality on the stable and unstable side respectively. The discontinuity is thus not believed to be an effect merely of stability. A second correction function which is continuous over all stabilities has therefore also been constructed. These two functions and the correction function from Horst (2006) have been compared to measured flux loss. Based on this comparison the continuous correction function is recommended for correcting scalar fluxes measured over sea. It should be noted, however, that this expression only describes the mean attenuation and has been constructed from measurements at 5 and 5.5 m above mean sea level.

The theoretical basis used in the development of the function for flux attenuation over land allows for a direct link between a spectral shape and the attenuation expression. This link has been preserved for the new expressions presented in this report. The spectral shape corresponding to the continuous correction function has been compared to measured mean cospectra and also to the cospectra from Horst (2006) corresponding to crosswind displacements.

At a height of 10 m and a sensor displacement of 0.2 m the mean flux attenuation is about 1.3-4% in the stability interval −1 < z/L < 1.5 when using the new correction functions presented in this report.

Die Surface Renewal Analysis wurde zur Bestimmung sensibler Wärmeflußdichten im bodennahen Bereich der atmosphärischen Grenzschicht genutzt und mit der Eddy - Korrelations - Methode verglichen. Dazu wurden beide Berechnungsmethoden auf Temperatur - und Vertikalwinddaten angewandt, die unter Verwendung von Strukturfunktionen simuliert wurden. Zur Überprüfung der Resultate wurden über zwei verschiedenen Unterlagen (Wiese und Düne) hochfrequente Zeitreihen von Temperatur und Vertikalwind gemessen und mit der Surface Renewal Analysis und der Eddy - Korrelations - Methode analysiert
The Surface Renewal Analysis was used to estimate the sensible heat flux density in the ground near area of the boundary layer. The results were compared with eddy correlation method. For it both methods were used to analyse temperature- and vertical velocity-data, which were simulated by the application of structure functions. Time series of high frequency temperature- and vertical velocity-data over two different canopies (meadow and dune) were measured to examine the results. The data were analysed with surface renewal analysis and eddy correlation

To understand and to predict the weather and climate, numerical models are important tools and it is crucial that the controlling processes are described correctly. Since 70% of the global surface is covered with water the description how the ocean and atmosphere communicates has a considerable impact. The ocean–atmosphere exchange occurs through transport of momentum (friction) and heat, governed by turbulent eddies. The sea surface is also an important source of turbulence in both directions. The scales of the turbulent eddies cannot be resolved in ocean and climate models. Therefore, the turbulent exchanges have to be related to mean variables, such as wind speed and temperature differences. By using measurements, new methods to describe the air–sea exchange during two specific processes were developed. These processes are the so-called UVCN-regime (Unstable Very Close to Neutral stratification) and swell, i.e. waves which are not produced by the local wind. These processes were included in an ocean model and in a regional atmospheric climate model and the impact was investigated. The UVCN-regime enhances the heat transport significantly during the autumn and winter months in the ocean model. This results in a shallower well-mixed surface layer in the ocean. Wind-following swell reduces the surface friction, which is very important for the atmosphere. Some secondary effects in the climate model are reduced low-level cloud cover and reduced precipitation by more than 10% over sea areas. Locally and for short periods the impact is large. It is important to include the UVCN-regime and the swell impact in models, to make simulations more reliable.

Die Surface Renewal Analysis wurde zur Bestimmung sensibler Wärmeflußdichten im bodennahen Bereich der atmosphärischen Grenzschicht genutzt und mit der Eddy - Korrelations - Methode verglichen. Dazu wurden beide Berechnungsmethoden auf Temperatur - und Vertikalwinddaten angewandt, die unter Verwendung von Strukturfunktionen simuliert wurden. Zur Überprüfung der Resultate wurden über zwei verschiedenen Unterlagen (Wiese und Düne) hochfrequente Zeitreihen von Temperatur und Vertikalwind gemessen und mit der Surface Renewal Analysis und der Eddy - Korrelations - Methode analysiert.
The Surface Renewal Analysis was used to estimate the sensible heat flux density in the ground near area of the boundary layer. The results were compared with eddy correlation method. For it both methods were used to analyse temperature- and vertical velocity-data, which were simulated by the application of structure functions. Time series of high frequency temperature- and vertical velocity-data over two different canopies (meadow and dune) were measured to examine the results. The data were analysed with surface renewal analysis and eddy correlation.

Approved for public release; distribution is unlimited
Variability of the MABL and its effect on the electromagnetic (EM) refractive structure around the Greenland Sea marginal ice zone were examined. Rawinsonde profiles and surface observations collected from 3 ships during MIZEX-87(20 March-11 April) served as the data set. A program, developed to calculate the refractivity at each vertical level of the rawinsonde profiles, also identified the levels at which trapping, superrefraction and subrefraction occurred. Temporal studies showed that a higher incidence of anomalous refractive layers occurred during periods when the region was under the influence of high pressure. More than 50% of the time, trapping and super-refractive layers were attributed to development of a capping inversion just above the MABL during these periods. Spatial studies showed that the refractive structure varied relative to distance from the ice edge as did the depth of the MABL. An upward slope in refractive layer heights was observed from the ice toward the open water. Significant spatial inhomogeneity was observed over horizontal ranges of less than 100 km. This was attributed to both the large-scale synoptic forcing affecting the region and to variations in the surface fluxes of heat and moisture over the ice and over the water. A range-dependent ray trace model developed at the Naval Ocean Systems Center was used to show how the ray paths of EM waves vary with a changing refractive structures. Keywords: Air water interactions, Greenland Sea, Atmospheric refraction, Electromagnetic wave propagation, Heat flux, Sea ice. Theses. (EDC)
http://archive.org/details/temporalspatialv00grot
Lieutenant, United States Navy

This study investigates the upper ocean circulation along the west Australian coast, based on recent observations (WOCE ICM6, 1994/96) and numerical output from the 1/6 degree Parallel Ocean Program model (POP11B 1993/97). Particularly, we identify the source regions of the Leeuwin Current, quantify its mean and seasonal variability in terms of volume, heat and salt transports, and examine its heat balance (cooling mechanism). This also leads to further understanding of the regional circulation associated with the Leeuwin Undercurrent, the Eastern Gyral Current and the southeast Indian Subtropical Gyre. The tropical and subtropical sources of the Leeuwin Current are understood from an online numerical particle tracking. Some of the new findings are the Tropical Indian Ocean source of the Leeuwin Current (in addition to the Indonesian Throughflow/Pacific); the Eastern Gyral Current as a recirculation of the South Equatorial Current; the subtropical source of the Leeuwin Current fed by relatively narrow subsurface-intensified eastward jets in the Subtropical Gyre, which are also a major source for the Subtropical Water (salinity maximum) as observed in the Leeuwin Undercurrent along the ICM6 section at 22 degrees S. The ICM6 current meter array reveals a rich vertical current structure near North West Cape (22 degrees S). The coastal part of the Leeuwin Current has dominant synoptic variability and occasionally contains large spikes in its transport time series arising from the passage of tropical cyclones. On the mean, it is weaker and shallower compared to further downstream, and it only transports Tropical Water, of a variable content. The Leeuwin Undercurrent carries Subtropical Water, South Indian Central Water and Antarctic Intermediate Water equatorward between 150/250 to 500/750 m. There is a poleward flow just below the undercurrent which advects a mixed Intermediate Water, partially associated with outflows from the Red Sea and Persian Gulf. Narrow bottom-intensified currents are also observed. The 5-year mean model Leeuwin Current is a year-round poleward flow between 22 degrees S and 34 degrees S. It progressively deepens, from 150 to 300 m depth. Latitudinal variations in its volume transport are a response to lateral inflows/outflows. It has double the transport at 34 degrees S (-2.2 Sv) compared to at 22 degrees S (-1.2 Sv). These model estimates, however, may underestimate the transport of the Leeuwin Current by 50%. Along its path, the current becomes cooler (6 degrees C), saltier (0.6 psu) and denser (2 kg m -3). At seasonal scales, a stronger poleward flow in May-June advects the warmest and freshest waters along the west Australian coast. This advection is apparently spun up by the arrival of a poleward Kelvin wave in April, and reinforced by a minimum in the equatorward wind stress during July. In the model heat balance, the Leeuwin Current is significantly cooled by the eddy heat flux divergence (4 degrees C out of 6 degrees C), associated with mechanisms operating at submonthly time scales. However, exactly which mechanisms it is not yet clear. Air-sea fluxes only account for ~30% of the cooling and seasonal rectification is negligible. The eddy heat divergence, originating over a narrow region along the outer edge of the Leeuwin Current, is responsible for a considerable warming of a vast area of the adjacent ocean interior, which is then associated with strong heat losses to the atmosphere. The model westward eddy heat flux estimates are considerably larger than those associated with long lived warm core eddies detaching from the Leeuwin Current and moving offshore. This suggests that these mesoscale features are not the main mechanism responsible for the cooling of the Leeuwin Current. We suspect instead that short lived warm core eddies might play an important role.

A novel type of precast, prestressed concrete structural element is being implemented in load-bearing systems in buildings. These structural elements combine the use of high-performance, self-consolidating concrete (HPSCC) and non-corroding carbon fibre reinforced polymer (CFRP) prestressing tendons; this produces highly optimized, slender structural elements with excellent serviceability and (presumed) extended service lives. More widely, the use of new construction techniques, innovative materials, and ground-breaking designs is increasingly commonplace in today's rapidly evolving building construction industry. However, the performance of these and other structural elements in fire is in general not well known and must be understood before these can be used with confidence in load-bearing applications where structural fire resistance is a concern. Structural fire testing has traditionally relied on the use of the standard fire resistance test (i.e. furnace test) for assuring regulatory compliance of structural elements and assemblies, and in many cases also for developing the scientific understanding of structural response to fire. Conceived in the early 1900s and fundamentally unchanged since then, the standard testing procedure is characterized by its high cost and low repeatability. A novel test method, the Heat-Transfer Rate Inducing System (H-TRIS), resulting from a mental shift associated with controlling the thermal exposure not by temperature (e.g. temperature measured by thermocouples) but rather by the time-history of incident heat flux, was conceived, developed, and validated within the scope of the work presented in this thesis. H-TRIS allows for experimental studies to be carried out with high repeatability, imposing rationally quantifiable thermal exposure, all at low economic and temporal cost. The research presented in this thesis fundamentally seeks to examine and understand the behaviour of CFRP prestressed HPSCC structural elements in fire, with emphasis placed on undesired 'premature' failure mechanisms linked to the occurrence of heat-induced concrete spalling and/or loss of bond between the pretensioned CFRP tendons and the concrete. Results from fire resistance tests presented herein show that, although compliant with testing standards, temperature distributions inside furnaces (5 to 10% deviation) appear to influence the occurrence of heat-induced concrete spalling for specimens tested simultaneously during a single test; fair comparison of test results is therefore questionable if thermal exposure variability is not explicitly considered. In line with the aims of the research presented in this thesis, H-TRIS is used to carry out multiple comprehensive studies on the occurrence of concrete spalling and bond behaviour of CFRP tendons; imposing a quantified, reproducible and rational thermal exposure. Test results led to the conclusion that a "one size fits all" approach for mitigating the risk of heat-induced concrete spalling (e.g. prescribed dose of polypropylene (PP) fibres included in fresh concrete), appears to be ineffective and inappropriate in some of the conditions examined. This work demonstrates that PP fibre cross section and individual fibre length can have an influence on the risk of spalling for the HPSCC mixes tested herein. The testing presented herein has convincingly shown, for the first time using multiple repeated tests under tightly controlled thermal and mechanical conditions, that spalling depends not only on the thermal gradients in concrete during heating but also on the size and restraint conditions of the tested specimen. Furthermore, observations from large scale standard fire resistance tests showed that loss of bond strength of pretensioned CFRP tendons occurred at a 'critical' temperature of the tendons in the heated region, irrespective of the temperature of the tendons at the prestress transfer length, in unheated overhangs. This contradicts conventional wisdom for the structural fire safety design of concrete elements pretensioned with CFRP, in which a minimum unheated overhang is generally prescribed. Overall, the research studies presented in this thesis showed that a rational and practical understanding of the behaviour of CFRP prestressed HPSCC structural elements during real fires is unlikely to be achieved only by performing additional standard fire resistance tests. Hence, H-TRIS presents an opportunity to help promote an industry-wide move away from the contemporary pass/fail and costly furnace testing environment. Recommendations for further research to achieve the above goal are provided.

Le travail presente est une etude experimentale des transferts turbulents de chaleur, humidite et quantite de mouvement dans la couche limite marine. La phase experimentale (experience toscane-t) s'est deroulee en mars 1985, au large de la baie d'audierne (finistere). Le principal vecteur utilise pour le travail presente est un avion instrumente pour la physique de l'atmosphere. Ce moyen a permis de determiner une topographie des caracteristiques turbulentes, sur une echelle horizontale de l'ordre de 50km sur 50km, et de calculer les flux par la methode des correlations. Les conditions experimentales rencontrees correspondent a des vents compris enre 3 et 12 metres par seconde et a des conditions d'instabilite caracterisees par des longueurs de monin obukhov negatives comprises entre 50 et 300 metres. La structure turbulente de la couche limite marine est presentee dans le cadre de la theorie de similitude. Les resultats obtenus sont en accord avec les donnees acquises en couche limite dynamique, marine ou continentale. Ils sont egalement compares aux caracteristiques turbulentes des couches limites convectives. La finalisation de cette etude est resumee au moyen d'une parametrisation des flux de surface. Celle-ci est utilisable dans les modeles de grande echelle et consiste a calculer les coefficients aerodynamiques. Dans les conditions experimentales de l'etude les valeurs obtenues sont les suivantes: 1. 8 10**(-3) pour la quantite de mouvement (cd::(10)); 1. 5 10**(-3) pour la chaleur sensible (ct::(10)); et 1. 5 10**(-3) pour la chaleur latente (cq::(10)); ces coefficients sont independants de l'echelle d'integration spatiale a laquelle ils ont ete determines (de 5 km sur 5 km a 50 km sur 50 km).

The Southwest Atlantic Ocean is characterized, in winter, by the presence of an oceanographic front between the Brazil Current (BC) and the Brazilian Coastal Current (BCC). The BC/BCC oceanographic front generates intense thermal horizontal gradients between cold waters of the southern Brazilian continental shelf, dominated by the BCC, and the offshore warm waters, dominated by the BC. This study analyses, for the first time in the known literature, the coupling mechanisms between the ocean and the atmosphere from observational data taken simultaneously during an oceanographic research cruise in the southern Brazilian coast during 11-21 June 2014. In this field experiment, atmospheric radiosondes were launched and hydrographic stations were taken to measure the ocean s temperature and salinity. The study area was chosen based on the local thermal gradients presented by the BC/BCC front. Five oceanographic transects were performed perpendicular to the coast starting at the locality of Paranaguá (Paraná State) and ending in Chuí (Rio Grande do Sul State).The winter meteorological and oceanographic features were considered in the determination of ship s route. The installation of a micrometeorological tower at the bow of the ship allowed the realization of direct measurements of heat, momentum and CO2 fluxes. This study analyses the large scale meteorological conditions and explores the behavior of the marine atmospheric boundary layer using radiosondes data taken in situ. In the period when the data were collect, typical winter conditions were observed in the study area, like the cold front passage associated to an incursion of a post-frontal cold air mass and an extratropical cyclone formation. Meteorological and oceanographic measurements performed by the instruments installed on the ship were utilized to estimate the heat fluxes through bulk formulas method. This estimates were lately compared to the heat fluxes measured directly by the sensors installed in the of the ship s bow. Measurements were obtained using the Eddy Covariance method, broadly used in micrometeorological research. To obtain the turbulent fluxes at the ocean-atmosphere interface adjustments in the observational data are necessary due to the ship s motion. During most of the study period, the sea surface temperature was higher than the air temperature, thus generating a heat transfer from the ocean to the atmosphere. The heat fluxes were commonly positive on both sides of the BC (warm)/BCC (cold) oceanographic front. However, there was some difference on the heat fluxes magnitude between the two sides of the front with more intense heat exchange on the BC side. The present results show that the intense thermal horizontal gradients between the BC and the BCC waters that occur during winter in the southern coast of Brazil, the transient atmospheric systems and the air thermal advection have an important role on the marine atmospheric boundary layer modulation and on the heat and CO2 fluxes between the ocean and the atmosphere. Meteorological and oceanographic observations are fundamental to widen our understanding of the processes occurring at the ocean-atmosphere interface which are known to have primary importance on weather and climate forecast.
O Oceano Atlântico Sudoeste é caracterizado, no inverno, pela presença de uma frente oceanográfica entre a Corrente do Brasil (CB) e a Corrente Costeira do Brasil (CCB). A frente oceanográfica CB/CCB gera intensos gradientes horizontais termais entre as águas frias da plataforma continental do Sul do Brasil, dominadas pela CCB, e águas quentes do oceano profundo, dominadas pela CB. Esse trabalho analisa, pela primeira vez na literatura conhecida, os mecanismos de acoplamento entre o oceano e a atmosfera a partir de dados observacionais da atmosfera e do oceano que foram tomados simultaneamente durante um cruzeiro de pesquisa oceanográfica na costa sul do Brasil entre 11 a 21 de junho de 2012. Nesse experimento, foram lançadas radiossondas atmosféricas e realizadas estações hidrográficas para medidas de temperatura e salinidade do oceano. A área de estudo foi escolhida com base no gradiente termal local apresentado pela frente CB/CCB. Foram realizados cinco transectos perperndiculares à costa sul do Brasil, iniciando-se na localidade de Paranaguá (PR) até o Chuí (Rio Grande do Sul). As características oceanográficas e meteorológicas de inverno foram consideradas na determinação da derrota do navio. A instalação de uma torre micrometeorológica na proa do navio permitiu a realização de medições diretas dos fluxos de calor, momentum e CO2. Este estudo analisa as condições meteorológicas de grande escala e investiga o comportamento da camada limite atmosférica marinha a partir dos dados in situ das radiossondagens. No período em que os dados foram coletados foram observadas condições atmosféricas típicas de inverno, como a passagem de frente fria associada à incursão de uma massa de ar frio pós-frontal e a formação de ciclone extratropical. Observações meteorológicas e oceanográficas realizadas pelos instrumentos instalados no navio foram utilizadas para estimar os fluxos de calor pelo método bulk formulas. Essas estimativas foram comparadas aos fluxos medidos diretamente pelos sensores instalados na proa do navio. As medidas são obtidas utilizando o método de Covariância de Vórtices, usado amplamente em pesquisas micrometeorológicas. Para obter os fluxos turbulentos na interação oceano-atmosfera são necessárias correções nos dados observados devido ao movimento do navio. Durante a maior parte do período estudo, a temperatura da superfície do mar esteve maior do que a temperatura do ar, gerando uma transferência de calor do oceano para atmosfera. Os fluxos de calor foram, geralmente, positivos em ambos os lados da frente oceanográfica CB (quente)/CCB (frio). Contudo, há diferença na magnitude dos fluxos de calor entre os dois lados da frente com a troca foi mais intensa no lado da CB. Os resultados apresentados mostram que os intensos gradientes horizontais termais entre as águas da CB e da CCB que ocorrem durante o inverno ao largo da costa do RS, os sistemas transientes e as advecções térmicas têm um papel importante na modulação da camada limite atmosférica marinha e nos fluxos de calor e CO2. Observações meteorológicas e oceanográficas são fundamentais para ampliar o entendimento dos processos que ocorrem na interface oceano-atmosfera e tem importância primária para a previsão do tempo e clima.

碩士
國立成功大學
造船工程學系
86
In the present study a three-dimensional transient inverse heat conductionproblem in solved using the Conjugate Gradient Method( CGM) and the generalpurpose commerical code CFX-4.2-baseed inverse algorithm to estimate the unknown boundary heat flux in any three-dimension irregular domain.The advantage of calling as a subroutine in the present inverse calculationlies in that many difficult but practial 3-D inverse problem can be solved under this construction.Results obtained by using the conjugate gradient method to solve this 3-Dinverse problems are justified based on the numerical experiments. It is cocluded the accurate boundary fluxes can be estimated by the conjugategradient methos except for the final time. The reason and improvement of this singularity are addressed. Finally, the effects of the measurementerrors on the inverse solution are discussed.

碩士
國立成功大學
機械工程學系
89
An integral analytical solution for non-Fourier heat conduction in a one-dimensional slab is found by Laplace transform. Comparisons of the results and those obtained by a finite-difference method show the validity of the present method. Next, using the analytical solution, a non-iteration scheme is developed to estimate the boundary heat flux from the temporal temperature distribution at the other boundary. Finally, the effects of the temperature error and the thickness of the slab are examined.

Thesis (M.S.)--University of Wisconsin--Madison, 1997.
Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 88-91).

Exchange of mass (water vapor), momentum, and energy between atmosphere andocean has profound influence on weather and climate. This exchange takes place at the air-sea interface, which is part of the marine atmospheric boundary layer. Various empirical relations are being used for estimating these fluxes in numericalweather and climate models but their accuracies are not sufficiently verified or tested over the Indian Ocean. The main difficulty is that vast areas of open oceans are not easily accessible. The marine environment is very corrosive and unattended long term and accurate measurements are extremely expensive. India has research ships that spend most of their time over the seas around India but that opportunity is yet to be exploited. To address this, an air-sea flux measurement system for operation on board research ships was planned. The system was tested on board Indian Research Vessels ORV SagarKanya during its cruise SK-296 in the Bay of Bengal (BoB) in July-August 2012, and NIO ship Sindhu Sadhana in June-July 2016. The complete set included instruments for measuring wind velocity, windspeed and direction, air and water temperature, humidity, pressure, all components of radiation and rainfall. In addition, ship motion was recorded at required sampling rate to correct for wind velocity. The set up facilitates the direct computation of sensible and latent heat fluxes using the eddy covariance method. In this thesis, design and installation of meteorological and ship motion sensors onboard research ships, data collection and quality control, computation of fluxes of heat, moisture and momentum using eddy covariance method and their comparison with those derived from bulk method are described. A set of sensors (hereafter, flux measuring system) were mounted on a retractable boom, ~7 m long forward of the bow to minimize the flow disturbance caused by the ship superstructures. The wind observed in the ship frame was corrected for ship motion contaminations. During the CTCZ cruise period true mean wind speed was over 10 m/s and true wind direction was South/South-Westerly. True windspeedis computed combiningdata from the anemometer a compass connected to AWS and a GPS. Turbulent fluxes were computed from motion-corrected time-series of high frequency velocity, water vapor, and air temperature data. Covariance latent heat flux, sensible heat flux, and wind stress were obtained by cross-correlating the motion-corrected vertical velocity with fast humidity fluctuations measured with anIR hygrometer, temperate fluctuation from sonic anemometer and motion-corrected horizontal windfluctuations from sonic anemometer, respectively. During the first attempt made in July-August 2012 as part of a cruise of CTCZ monsoonresearch program, observations were mainly taken in the North Bay of Bengal. The mean air-temperature and surface pressure were ~28 Deg C and ~998 hPa, respectively. Relative humidity was ~80%. Average wind speed varied in the range 4-12 m/s. The mean latent heat flux was 145 W/m2 , sensible heat flux was ~3 W/m2 and average sea-air temperature difference was ~ 0.7°C. The Bay of Bengal boundary layer experiment (BoBBLE) was conducted during June-July 2016 and the NIO research ship Sindhu Sadhana was deployed. The same suite of sensors installed during CTCZ were used during BoBBLE. During daytime, peaks of hourly net heat fluxes (Qnet ) were around 600 Wm-2(positive if into the sea), whereas, night time values were around -250 W m-2. Sea surface temperature was always >28°C and maximum air temperature exceeded 29°C. During the experimental period the mean Qnet was around -24 Wm-2 from both eddy covariance and conventional bulk methods, but there are significant differences on individual days.The new flux system gives fluxes which are superior to what was available before.