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1
Wiyo, Kenneth Alfred Wiskot. "Measurements and modelling of fertilizer concentrations in subsurface drain flow from a potato field". Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60542.
Testo completoAbstract (sommario):
A 4.87 hectare potato field at St. Leonard d'Aston, Quebec was instrumented to measure surface runoff and tile drain flow over the 2 year growing season period, 1989-1990. The soil type was a Ste. Jude sandy loam. Several soil and water parameters and NPK concentrations in runoff were measured. The CREAMS (Chemicals, Runoff and Erosion from Agricultural Management Systems) computer simulation model was validated for the study site.Observed N concentrations in tile drain flow exceeded the Canadian water quality guideline of 10 mg/L. Observed P concentrations were less than 0.01 mg/L; and K concentrations, for the most part, exceeded 10 mg/L.
CREAMS overpredicted event surface runoff depths, and underpredicted event percolation depths. However, total monthly surface runoff and percolation depths closely matched observed values.
CREAMS overpredicted event nitrate concentrations in tile drain flow. There was a poor match between predicted and observed event nitrate concentrations in tile drain flow (coefficient of predictability, CP$ sb{ rm A}$ = 104.95). However, predicted total monthly nitrate load closely matched observed values (CP$ sb{ rm A}$ = 0.84). Total monthly and seasonal nitrate loads in tile drain flow were underpredicted.
2
Woods, Juliette Aimi. "Numerical accuracy of variable-density groundwater flow and solute transport simulations". Title page, contents and abstract only, 2004. http://web4.library.adelaide.edu.au/theses/09PH/09phw8941.pdf.
Testo completo
3
Colautti, Dennis. "Modelling meteorological and substrate influences on peatland hydraulic gradient reversals". Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33734.
Testo completoAbstract (sommario):
A hydrological modelling effort using MODFLOW was undertaken in order to determine the relative importance of some of the factors influencing hydraulic gradient reversals in peatlands. Model domains were of two types, large raised bog type (LRBT) and kettle bog type (KBT), and were made to undergo various levels of meteorological forcing (water deficit). Substrate, too, was varied in order to determine its importance on reversals. Domain-wide reversals were successfully simulated in LRBT systems, but not in KBT systems. Although simulated flow patterns matched field-observed patterns, both pre- and post-drought, simulated reversals occurred more quickly than in the field. This may be due to insufficiently distributed parameters, such as hydraulic conductivity. Reversals were easily terminated by simulating non-drought conditions. In the LRBT system, reversal duration decreased, and time-to-reversal increased, with a decrease in drought severity. Increasing drought severity in KBT systems had the opposite effect on the duration of semi-reversed flow patterns, suggesting a possibly different/additional mechanism for flow reversals in KBT systems. Hydraulic conductivity had an appreciable effect on flow reversal evolution, though neither changing porosity, nor differences in catotelm layering had a great effect.
4
Singhal, Alka. "Spatial variability in ground-water movement in Delaware County, Indiana : a GIS based model". Virtual Press, 2004. http://liblink.bsu.edu/uhtbin/catkey/1306859.
Testo completoAbstract (sommario):
A study was undertaken to better understand the hydrogeologic framework of the Delaware County, Indiana. Arc View GIS 3-D and Spatial Analysts along with VISUAL MODFLOW are used to study the flow patterns by developing a 3-D model of major aquifers in the county, both glacial and bedrock. The GIS platform facilitates the time consuming task of preparing data input and output. In addition, major recharge zones are also identified in GIS using soil and slope data.The bedrock of Delaware County is composed of Silurian bedrock, which is overlain by glacial drift. The drift is mostly till that is interbedded with eight sand and gravel layers which are horizontal and discontinuous. Both, bedrock and sand & gravel glacial aquifers are good sources of groundwater in the county. More than 3000 water wells are located in the area. It is very interesting to note that 50% of the water-wells in the area are in confined sand and gravel and the remaining wells are in carbonaceous bedrock. The bedrock contains numerous preglacial karsts valley systems which are areas of high transmissivity solution features, also adding further interest to modeling this region.The hydraulic conductivity of sand and gravel is assumed to be 0.0015 m/s whereas for bedrock 0.00025 m/s is used. The streambeds in the area are also the source of groundwater discharge. The hydraulic conductivity of streambed is equal to 0.00028 m/s. Recharge to the area occurs as net recharge, which varies spatially depending on the nature of soil.Several simplifying assumptions were made for the conceptualization and simulation of flow in the basins. The main assumptions are as follows: 1) groundwater is in steady-state, 2) pumping does not significantly affect the level of hydraulic heads; therefore only high capacity pumping wells are simulated, 3) Net recharge from precipitation varies spatially, 4) flow in the bedrock aquifer occurs in the uppermost 40 m and is horizontal 5) vertical flow is assumed to be controlled by intervening sand and gravel units. Ground-water flow in the basins was conceptualized as a three-dimensional flow system. The model boundaries selected to represent natural hydrologic boundaries include (1) river leakage boundaries along major rivers; (2) a constant head boundary around the aquifer boundaries; (3) a general head boundary along the major streams; (4) drain boundaries along major drains; and 5) Evapotranspiration losses.The simulated region is an area of 398 square miles. The model consists of over 3600 cells and employed a regular grid spacing of 6o x 60. A variable grid was designed to provide additional detail in areas of special interest and thus allowed these areas to be simulated more accurately in the model.The model was calibrated using a manual trial-and-error adjustment of parameters. Hydraulic conductivity values, and streambed conductance were adjusted during successive simulations until the flow pattern matches the regional flow direction as computed from the water-well derived (static water level) potentiometric surface. The computed potentiometric surface is an adequate or reasonable match on a regional scale, with the general trend of SE-NW. It is observed that the model is extremely sensitive to changes in horizontal hydraulic conductivity and recharge in the form of precipitation. The model is least sensitive to streambed vertical hydraulic conductivity.The water budget for the calibrated model represents the distribution of groundwater inflow and outflow during calibration. The data indicate that 16.5% of the inflow to the modeled groundwater system is flow across model boundaries and 83% from effective recharge from precipitation, and the rest from streams and rivers. Outflow consists of 2% pumpage, 5% seepage to streams and drains, and 93% is flow across boundaries.It is expected that this study will be beneficial to improve the understanding of groundwater in Delaware County, including both vertical and horizontal flow and interaction of flow between surface and groundwater. Also, the results of the modeling study can be used as a predictive tool for long-term management and monitoring of water resources in the region.Department of Geology
5
Lee, Chun-kwong, e 李振光. "Computer modelling and simulation of geothermal heat pump and ground-coupled liquid desiccant air conditioning systems in sub-tropicalregions". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B41290768.
Testo completo
6
Lee, Chun-kwong. "Computer modelling and simulation of geothermal heat pump and ground-coupled liquid desiccant air conditioning systems in sub-tropical regions". Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/B41290768.
Testo completo
7
Wang, Li. "Simulation of soil water movement model (SWaMM) using the Spider Distributed System". CSUSB ScholarWorks, 2003. https://scholarworks.lib.csusb.edu/etd-project/2419.
Testo completoAbstract (sommario):
This project implements a real application on the Spider II, which is a simulation of Soil Water Movement Model. The main objectives of this project were to develop a parallel and distributed algorithm for the Soil Water Model; implement the Soil Water Movement Simulation model on the Spider II distributed system and to evaluate the performance of simulating the Soil Water Movement Model on Spider II.
8
Silliman, Stephen Edward Joseph 1957. "Stochastic analysis of high-permeability paths in the subsurface". Diss., The University of Arizona, 1986. http://hdl.handle.net/10150/191120.
Testo completoAbstract (sommario):
Subsurface fluids may travel along paths having a minimum permeabilility greater than the effective permeability of the rock. This may have an important impact on contaminant migration. A stochastic approach related to percolation theory is advanced to address the question of what is the probability that a high permeability path extends across a given volume of the subsurface. The answer is sought numerically through subdividing the volume of interest into a three-dimensional grid of elements and assigning a random permeability to each element. Four permeability processes are considered: 1) Stationary with independence between grid elements; 2) Stationary and autocorrelated; 3) Nonstationary due to conditioning on measured values; and 4) Random rock volume included in grid. The results utilizing data from fractured granites suggest that in large grids, at least one path having a minimum permeability in excess of the "effective" rock permeability will cross the grid. Inclusion of autocorrelation causes an increase in the expected value of the minimum permeability of such a path. It also results in a significantly increased variance of this permeability. Conditioning on field permeabilities reduces the variance of this value over that obtained by unconditional, correlated simulation, but still produces a variance greater than that obtained when independence was assumed. When conditioning is performed, the mean of the minimum permeabilities along these paths is dependent on the principal axis of the path. Finally, including a random rock volume by allowing the length of the grid to be random increases the variance of the minimum permeability.
9
Baron, Dirk. "Analysis and Numerical Simulation of the Ground Water System at the Bonneville Navigation Lock Site, Oregon". PDXScholar, 1990. https://pdxscholar.library.pdx.edu/open_access_etds/4027.
Testo completoAbstract (sommario):
As part of the new navigation lock for Bonneville Dam a new water source for the Bonneville Fish Hatchery must be supplied. The hatchery is located on the Oregon side of the Columbia River downstream of the dam. It requires large quantities of water free from chemical and biological contamination. In addition, the water has to be in a narrow temperature range. Currently the fish hatchery receives its water from a well field that is located on the alluvial terrace downstream of Bonneville Dam. The well field lies in the proposed approach channel for the new lock and has to be abandoned during construction of the lock. For the continued water supply of the hatchery, a new well field will be developed north of the approach channel. Early in the planning phase for the new lock, concerns were raised about the potential impact of the relocation of the well field and the excavation of the new approach channel on the hatchery. To assess these concerns and to assure a continuous water supply during and after construction, a hydrogeologic investigation was initiated. Within the framework of the investigation this study focuses on the analysis of pumping test data and the development of a three-dimensional ground water flow model for the site.
In the first phase of the study, data from eight pumping tests were analyzed. Hydrogeologic properties of the sedimentary units that make up the downstream terrace were determined. The focus was the pre-slide alluvium (PSA) aquifer, the water source for the existing and the future well field. In addition, the nature and location of hydrogeologic boundaries for the ground water system were determined. The results, in conjunction with information from subsurface exploration and laboratory tests, were used to develop a conceptual understanding of the ground water system at the site. The PSA aquifer receives its recharge primarily from leakage through the overlying confining layers over a large area. A direct connection between the Columbia River and the PSA aquifer could not be detected. They appear to be separated by a continuous aquitard layer or by a layer of fine-grained sediments on the river bottom.
Based on these findings, in the second phase of the study, the ground water modeling program HST3D (Kipp, 1987) was used to develop a three-dimensional ground water model for the site. The model was calibrated with data from one of the pumping tests. The calibration was then verified with a second set of conditions including pumping from shallow and deep wells. Water levels in the deep PSA aquifer and the shallow unconfined aquifer were successfully matched. A satisfactory match of observed conditions was possible with only slight modifications of the hydrogeologic parameters determined by pumping test analysis and based on the conceptual model developed in the first phase of the study. It appears that a continuous aquitard layer separating the Columbia River and the PSA aquifer, with the aquifer receiving recharge through vertical leakage over a large area, is a valid representation of the aquifer system.
10
Pischel, Esther Maria. "Investigating the Link Between Surface Water and Groundwater in the Tule Lake Subbasin, Oregon and California". PDXScholar, 2014. https://pdxscholar.library.pdx.edu/open_access_etds/1941.
Testo completoAbstract (sommario):
Water allocation in the upper Klamath Basin of Oregon and California has been challenging. Irrigators have increasingly turned to groundwater to make up for surface water shortages because of shifts in allocation toward in-stream flows for Endangered Species Act listed fishes. The largest increase in groundwater pumping has been in and around the Bureau of Reclamation's Klamath Irrigation Project, which includes the Tule Lake subbasin in the southern part of the upper Klamath Basin. Previous groundwater flow model simulations indicate that water level declines from pumping may result in decreased flow to agricultural drains in the Tule Lake subbasin. Agricultural drains on the Klamath Project are an important source of water for downstream irrigators and for the Tule Lake and Lower Klamath Lake National Wildlife Refuges. To better assess the impact of increased pumping on drain flow and on the water balance of the groundwater system, flow data from agricultural drains were evaluated to investigate the changes that have taken place in groundwater discharge to drains since pumping volumes increased. Additionally, a fine-grid groundwater model of the Tule Lake subbasin was developed based on the existing regional flow model. The fine-grid model has sufficient vertical and horizontal resolution to simulate vertical head gradients, takes advantage of time-series data from 38 observation wells for model calibration, and allows agricultural drains to be more explicitly represented. Results of the drain flow analysis show that the groundwater discharge to agricultural drains has decreased by approximately 4000 hectare-meters from the 1997-2000 average discharge. Most of this decrease takes place in the northern and southeastern portions of the subbasin. Results of the groundwater model show that the initial source of water to wells is groundwater storage. By 2006, approximately 56% of the water from wells is sourced from agricultural drains.
11
Griffin, D. J. K. "Upscaling techniques for groundwater flow and transport simulation". Thesis, University of Newcastle Upon Tyne, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360322.
Testo completo
12
Hussain, Sardar Muhammad. "Simulation of groundwater flow by the analytic element method". Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/55/55134/tde-07122017-084556/.
Testo completoAbstract (sommario):
Groundwater studies face computational limitations when providing local detail within regional models. The researchers are concentrated on applying the numerical models to minimize the difference between the physical reality and the implemented numerical model by considering the minimum computational cost. This work consists of the study of line-elements (such as line-doublets, circles, polygons, fractures) using the Analytic Element Method (AEM) for groundwater flow. In this work, we consider the study of two-dimensional groundwater flow in fractured porous media by the Analytic Element Method. We develop a numerical solution based on a series expansion for a problem with more than one fracture. Each fracture has an influence that can be expanded in a series that satisfies Laplaces equation exactly. In the series expansion, the unknown coefficients are obtained from the discharge potentials of all other elements that are related to the expansion coefficients. Sizes, locations and conductivities for all inhomogeneities are selected arbitrarily. This work also discusses a matrix method obtained by imposing the intern boundary conditions for the Analytic Element Method. The convergence analysis of a Gauss-Seidel type iterative method is also discussed.Estudos de águas subterrâneas enfrentam limitações computacionais ao fornecer detalhes locais em modelos regionais. Os pesquisadores estão concentrados na aplicação dos modelos numéricos para minimizar a diferença entre a realidade física e o modelo numérico implementado considerando o custo computacional mínimo. Este trabalho consiste no estudo de elementos de linha (como line-doublets, círculos, polígonos, fraturas) usando o Método de Elemento Analítico (AEM) para o fluxo de águas subterrâneas. Neste trabalho, consideramos o estudo do fluxo bidimensional de águas subterrâneas em meios porosos fraturados pelo Método dos Elementos Analíticos. Desenvolvemos uma solução numérica baseada em uma expansão em série para um problema com mais de uma fratura. Cada fratura tem uma influência que pode ser expandida em uma série que satisfaça exatamente a equação de Laplace. Na expansão da série, os coeficientes desconhecidos são obtidos a partir dos potenciais de descarga de todos os outros elementos que estão relacionados aos coeficientes de expansão. Tamanhos, locais e condutividades para todas as não-homogeneidades são arbitrariamente selecionados. Este trabalho também discute o método da matriz obtido impondo as condições de contorno do interno para o Método do Elemento Analítico. A análise de convergência de um método iterativo tipo Gauss-Seidel também é discutida.
13
Kuhlman, Kristopher Lee. "Laplace Transform Analytic Element Method for Transient Groundwater Flow Simulation". Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/193735.
Testo completoAbstract (sommario):
The Laplace transform analytic element method (LT-AEM), applies the traditionally steady-state analytic element method (AEM) to the Laplace-transformed diffusion equation (Furman and Neuman, 2003). This strategy preserves the accuracy and elegance of the AEM while extending the method to transient phenomena. The approach taken here utilizes eigenfunction expansion to derive analytic solutions to the modified Helmholtz equation, then back-transforms the LT-AEM results with a numerical inverse Laplace transform algorithm. The two-dimensional elements derived here include the point, circle, line segment, ellipse, and infinite line, corresponding to polar, elliptical and Cartesian coordinates. Each element is derived for the simplest useful case, an impulse response due to a confined, transient, single-aquifer source. The extension of these elements to include effects due to leaky, unconfined, multi-aquifer, wellbore storage, and inertia is shown for a few simple elements (point and line), with ready extension to other elements. General temporal behavior is achieved using convolution between these impulse and general time functions; convolution allows the spatial and temporal components of an element to be handled independently.Comparisons are made between inverse Laplace transform algorithms; the accelerated Fourier series approach of de Hoog et al. (1982) is found to be the most appropriate for LT-AEM applications. An application and synthetic examples are shown for several illustrative forward and parameter estimation simulations to illustrate LT-AEM capabilities. Extension of LT-AEM to three-dimensional flow and non-linear infiltration are discussed.
14
Myers, Barry. "Simulation of Groundwater Flow in Cache Valley, Utah and Idaho". DigitalCommons@USU, 2003. https://digitalcommons.usu.edu/etd/6728.
Testo completoAbstract (sommario):
A groundwater model of Cache Valley was created using MODFLOW. Steady-state calibration of the model demonstrated that recharge to the lower confined aquifer may occur along the margin of the valley that borders the Wellsville Mountains and the Bear River Range. Steady-state calibration also showed that discharge from the unconfined aquifer may occur along the eastern and western margins of the valley in both the Utah and the Idaho portions of the valley. Two simulations were run with increased pumping of 3 5 cubic feet per second (1 cubic meter per second) from the principal aquifer. The first simulation was run with the average annual precipitation value of 1.2 feet per year (0.36 meters per year), while the second was run with a less than average annual precipitation value of 1 foot per year (0.3 meters per year). The first simulation produced very little change within the unconfined aquifer. The discharge from the groundwater system through springs, seepage to streams, evapotranspiration, and general head boundaries remained unchanged with the increase in discharge through pumping. This indicates that the two continuous, confining layers that blanket the valley may serve as a barrier to groundwater flow between the unconfined and lower confined aquifer. The increased pumping within the principal aquifer did not stimulate increased recharge along the western margin of the valley. This indicates that true steady-state conditions were not achieved in the amount of time that the model had indicated. During the second simulation, decreased recharge to the groundwater system through infiltration of precipitation caused a decrease in discharge from the groundwater system through seepage to streams, springs, evapotranspiration, and general head boundaries. The increased pumping within the principal aquifer also did not stimulate increased recharge along the western margin of the valley. As with the first simulation, this indicates that true steady-state conditions were not achieved in the amount of time that the model had indicated. A sensitivity analysis of the model concluded that the hydraulic conductivity of the two continuous, confining layers that blanket the valley proved to have a relatively substantial impact on the water levels in the confined aquifers. The sensitivity analysis also showed that altering the vertical hydraulic conductivity of the lower confined aquifer produced minimal head changes.
15
Mgaya, Prosper. "A fundamental flow model for simulation of the groundwater flow in saturated rock fractures". 京都大学 (Kyoto University), 2006. http://hdl.handle.net/2433/136146.
Testo completo
16
Shafike, Nabil Girgis. "Groundwater flow simulations and management under imprecise parameters". Diss., The University of Arizona, 1994. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_e9791_1994_103_sip1_w.pdf&type=application/pdf.
Testo completo
17
Lang, Patrick Timothy. "Simulation of groundwater flow to assess the effects of groundwater pumping and canal lining in the Mesilla Basin of Dona Ana County, New Mexico and El Paso County, Texas". Thesis, The University of Arizona, 1994. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_etd_hy0225_sip1_w.pdf&type=application/pdf.
Testo completo
18
Weeden, A. Curtis Jr, e Thomas III Maddock. "Simulation Of Groundwater Flow In The Rincon Valley Area And Mesilla Basin, New Mexico And Texas". Department of Hydrology and Water Resources, University of Arizona (Tucson, AZ), 1999. http://hdl.handle.net/10150/617629.
Testo completoAbstract (sommario):
A groundwater flow model was constructed for the Rincon Valley area and Mesilla
Basin. The system is dominated by the complex interaction of the Rio Grande, canals, laterals,
and drains with groundwater pumping. The primary purpose of the model was to aid the New
Mexico -Texas Water Commission in assessing options for water resources development in the
Lower Rio Grand Basin from Caballo Reservoir in New Mexico to El Paso, Texas. One such
assessment was to evaluate the effect of secondary irrigation releases from Caballo Reservoir on
the water budget. In addition, the model will eventually be linked to a surface water model
(BESTSM) being utilized by the New Mexico -Texas Water Commission to evaluate water
supply alternatives for El Paso, Texas.
Stress periods were specified on a seasonal basis, a primary irrigation season from March
through October and a secondary irrigation season from November through February. Analysis
of model output indicates that groundwater pumping decreases Rio Grande flows, secondary
irrigation season releases do not alter the water budget significantly, and that recharge and
discharge from aquifer storage are strongly related to the season.
19
Batten, Paul. "Compressible flow simulation on a parallel computer". Thesis, University of Southampton, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358770.
Testo completo
20
Gillespie, Jennifer L. "Modelling and computer simulation of patient flow". Thesis, Ulster University, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.646847.
Testo completoAbstract (sommario):
The population of the United Kingdom is increasingly ageing and diseases, like cancer and stroke, are becoming more common in our society. This is having a detrimental affect on the performance of the National Health Service. Various schemes and services have been introduced to increase efficiency, and key performance indicators help to identify areas of best practice. By realistically modelling healthcare facilities with analytic and simulation models, based on queueing theory, we can provide detailed information to healthcare managers and clinicians. These models can help to identify issues and cost inefficiencies for early intervention. Analytic models are less data and computationally intensive, and provide results in a quick time frame compared to simulation models. However, they tend to be mathematically complex which means healthcare managers can find them difficult to understand, and are more reluctant to implement the solutions. Simulations are more data and computationally intensive compared to analytic models, but they are much easier to explain to healthcare managers when they are built in a user friendly environment. This means that managers tend to be more willing to introduce the results of the model into their department. Therefore, we use both analytic and simulation models in this work to utilise the benefits of both techniques. In this body of work a novel analytic cost model has been presented for a system which can be regarded as a network of M/M/∞ queues. The model considers the flow of patients through primary and secondary care, and is based on a mixture of Coxian phase-type models with multiple absorbing states. Costs are attached to each state of the model allowing the average cost per patient in the system to be calculated. We also provide a model which assesses whether the implementation of a new intervention is cost-effective. The model calculates the maximum cost the intervention can incur before the benefits no longer outweigh the cost of administering it. These analytic models have been applied to stroke patients deemed eligible for thrombolysis in order to assess the cost-effectiveness of thrombolytic therapy. We also present a novel simulation model for stroke patients, who are eligible for thrombolysis, in order to validate our analytic models. 'What-If' scenarios and Probabilistic Sensitivity Analysis have also been carried out to provide healthcare managers with more confidence in our models. An analytic model has been presented for a complex system of M / M / c queues in steady state. The model analyses the system to find bottlenecks and assesses whether the staff are being efficiently utilised. Two resource allocation models have then been defined: the first determines the minimum number of resources required within the department, and the second efficiently distributes the resources throughout the department. These resource allocation models have been applied to orthopaedic Integrated Clinical Assessment and Treatment Service (ICATS) data to reduce the current queues within the department. A novel simulation model has also been created for orthopaedic ICATS which includes extra variation and realistic features. This allows us to assess how robust and reliable our analytic models are, as the results are applied to our simulation model which has different assumptions. The novel analytic models provide very similar results to the simulation models built for each healthcare environment. This implies that our analytic models are robust and reliable even when applied to a department which includes different assumptions. Therefore, our analytic models will provide reliable results when healthcare managers need to make decisions in a short time frame. Simulation models have been found to be a good validation technique for analytic models, as healthcare managers understand them better. Extra components can also be easily included within a simulation model, such as complex distributions to represent the inter-arrival and service rate, and realistic features such as shift patterns.
21
Mock, Peter Allen. "New taxonomy of clastic sedimentary structures and a procedure for its use in the simulation of groundwater flow". Diss., The University of Arizona, 1997. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_e9791_1997_395_sip1_w.pdf&type=application/pdf.
Testo completo
22
Shrestha, Surendra Prakash. "An effective medium approximation and Monte Carlo simulation in subsurface flow modeling". Diss., Virginia Tech, 1993. http://hdl.handle.net/10919/38642.
Testo completo
23
Solomon, Luiza. "Learning and flow control in optimistic simulation". Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=29475.
Testo completoAbstract (sommario):
This thesis has two main contributions. The first contribution is the development of a modular, easy-to-use Time Warp simulation engine targeted towards distributed-memory environments. The second contribution is the analysis and experimental verification of the performance of the flow control algorithm proposed by Choe in a distributed-memory environment.The Time Warp simulation engine TWSIM provides our laboratory with a research medium for Time Warp simulations in a distributed-memory environment such as a network of workstations. The modular design of TWSIM allows for easy integration of any new simulation application and for fast testing of optimizations and improvements to the Time Warp mechanism. Its compact size and object-oriented implementation using the C++ programming language result in a short learning curve for future users and developers.
The flow control algorithm proposed by Choe was implemented and analyzed with the aid of the TWSIM simulation engine. The algorithm makes use of stochastic learning automata to balance simulations loads by continuously regulating the flow of events between processors during the course of the simulation. Three different load metrics are considered: memory usage, virtual time, and a space-time product of the first two metrics. The algorithm was tested with two different simulation applications: a queuing network simulation and a Personal Communication Services (PCS) simulation. Results show that the flow control algorithm reduces the memory usage; the number of rollbacks and the number of antievents at the expense of the simulation time. As well, it becomes apparent that the behaviour of the flow control algorithm is not a consequence of learning.
Finally, we discuss a number of approaches to learning and flow control using the outlines of the flow control algorithm, and we consider the extent of the performance improvement to be expected from memory-based schemes for limiting Time Warp optimism in a distributed-memory environment.
24
Daniel, Michael M. "Multiresolution statistical modeling with application to modeling groundwater flow". Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/10749.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1997.Includes bibliographical references (p. 205-211).
by Michael M. Daniel.
Ph.D.
25
Hill, David Paul. "The computer simulation of dispersed two-phase flow". Thesis, Imperial College London, 1998. http://hdl.handle.net/10044/1/8733.
Testo completo
26
Brown, David Joseph. "Computer simulation of discrete particle flow through hoppers". Thesis, University of Nottingham, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317014.
Testo completo
27
Schepper, Guillaume de. "Simulating surface water and groundwater flow dynamics in tile-drained catchments". Doctoral thesis, Université Laval, 2015. http://hdl.handle.net/20.500.11794/26532.
Testo completoAbstract (sommario):
Pratique agricole répandue dans les champs sujets à l’accumulation d’eau en surface, le drainage souterrain améliore la productivité des cultures et réduit les risques de stagnation d’eau. La contribution significative du drainage sur les bilans d’eau à l’échelle de bassins versants, et sur les problèmes de contamination dus à l’épandage d’engrais et de fertilisant, a régulièrement été soulignée. Les écoulements d’eau souterraine associés au drainage étant souvent inconnus, leur représentation par modélisation numérique reste un défi majeur. Avant de considérer le transport d’espèces chimiques ou de sédiments, il est essentiel de simuler correctement les écoulements d’eau souterraine en milieu drainé. Dans cette perspective, le modèle HydroGeoSphere a été appliqué à deux bassins versants agricoles drainés du Danemark. Un modèle de référence a été développé à l’échelle d’une parcelle dans le bassin versant de Lillebæk pour tester une série de concepts de drainage dans une zone drainée de 3.5 ha. Le but était de définir une méthode de modélisation adaptée aux réseaux de drainage complexes à grande échelle. Les simulations ont indiqué qu’une simplification du réseau de drainage ou que l’utilisation d’un milieu équivalent sont donc des options appropriées pour éviter les maillages hautement discrétisés. Le calage des modèles reste cependant nécessaire. Afin de simuler les variations saisonnières des écoulements de drainage, un modèle a ensuite été créé à l’échelle du bassin versant de Fensholt, couvrant 6 km2 et comprenant deux réseaux de drainage complexes. Ces derniers ont été simplifiés en gardant les drains collecteurs principaux, comme suggéré par l’étude de Lillebæk. Un calage du modèle par rapport aux débits de drainage a été réalisé : les dynamiques d’écoulement ont été correctement simulées, avec une faible erreur de volumes cumulatifs drainés par rapport aux observations. Le cas de Fensholt a permis de valider les conclusions des tests de Lillebæk, ces résultats ouvrant des perspectives de modélisation du drainage lié à des questions de transport.Tile drainage is a common agricultural management practice in plots prone to ponding issues. Drainage enhances crop productivity and reduces waterlogging risks. Studies over the last few decades have highlighted the significant contribution of subsurface drainage to catchments water balance and contamination issues related to manure or fertilizer application at the soil surface. Groundwater flow patterns associated with drainage are often unknown and their representation in numerical models, although powerful analysis tools, is still a major challenge. Before considering chemical species or sediment transport, an accurate water flow simulation is essential. The integrated fully-coupled hydrological HydroGeoSphere code was applied to two highly tile-drained agricultural catchments of Denmark (Lillebæk and Fensholt) in the present work. A first model was developed at the field scale from the Lillebæk catchment. A reference model was set and various drainage concepts and boundary conditions were tested in a 3.5 ha tile-drained area to find a suitable option in terms of model performance and computing time for larger scale modeling of complex drainage networks. Simulations suggested that a simplification of the geometry of the drainage network or using an equivalent-medium layer are suitable options for avoiding highly discretized meshes, but further model calibration is required. A catchment scale model was subsequently built in Fensholt, covering 6 km2 and including two complex drainage networks. The aim was to perform a year-round simulation accounting for variations in seasonal drainage flow. Both networks were simplified with the main collecting drains kept in the model, as suggested by the Lillebæk study. Calibration against hourly measured drainage discharge data was performed resulting in a good model performance. Drainage flow and flow dynamics were accurately simulated, with low cumulative error in drainage volume. The Fensholt case validated the Lillebæk test conclusions, allowing for further drainage modeling linked with transport issues.
28
Neaville, Chris C. "Hydrogeology and simulation of ground-water and surface-water flow in Pinal Creek Basin, Gila County, Arizona". Thesis, The University of Arizona, 1991. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_e9791_1991_400_sip1_w.pdf&type=application/pdf.
Testo completo
29
Walton, Anthony G. "Computer simulation of liquid flow patterns on distillation trays". Thesis, Aston University, 1995. http://publications.aston.ac.uk/9586/.
Testo completoAbstract (sommario):
This thesis describes work carried out to improve the fundamental modelling of liquid flows on distillation trays. A mathematical model is presented based on the principles of computerised fluid dynamics. It models the liquid flow in the horizontal directions allowing for the effects of the vapour through the use of an increased liquid turbulence, modelled by an eddy viscosity, and a resistance to liquid flow caused by the vapour being accelerated horizontally by the liquid. The resultant equations are similar to the Navier-Stokes equations with the addition of a resistance term. A mass-transfer model is used to calculate liquid concentration profiles and tray efficiencies. A heat and mass transfer analogy is used to compare theoretical concentration profiles to experimental water-cooling data obtained from a 2.44 metre diameter air-water distillation simulation rig. The ratios of air to water flow rates are varied in order to simulate three pressures: vacuum, atmospheric pressure and moderate pressure. For simulated atmospheric and moderate pressure distillation, the fluid mechanical model constantly over-predicts tray efficiencies with an accuracy of between +1.7% and +11.3%. This compares to -1.8% to -10.9% for the stagnant regions model (Porter et al. 1972) and +12.8% to +34.7% for the plug flow plus back-mixing model (Gerster et al. 1958). The model fails to predict the flow patterns and tray efficiencies for vacuum simulation due to the change in the mechanism of liquid transport, from a liquid continuous layer to a spray as the liquid flow-rate is reduced. This spray is not taken into account in the development of the fluid mechanical model.
30
Havard, Peter. "Linkflow, a linked saturated-unsaturated water flow computer model for drainage and subirrigation". Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=41608.
Testo completoAbstract (sommario):
A computer simulation model, LINKFLOW, has been developed to simulate the movement of water during various water table management practices, such as subsurface drainage, controlled drainage and subirrigation. Water movement is simulated to, or from, a buried tile drainage system through a heterogeneous and anisotropic soil to a zone of water extraction by plant roots and the atmosphere. The computer package links a newly-developed one-dimensional unsaturated ground water flow model to a three-dimensional saturated water flow model that was modified for the linkage and for simulating water flow under different water table management systems and varying climatic conditions. The movement of water is determined for a region of the field and the model can show the effectiveness of a water table management scheme to meet moisture conditions for crop growth for a wide range of soil, topographical, drain layout and weather conditions. LINKFLOW was validated and verified with measurements on subsurface drainage, controlled drainage and subirrigation systems in a corn field in southwestern Quebec. The model provides a powerful tool for the design and evaluation of water table management systems, and it can assist in developing control strategies for efficient management of water resources. LINKFLOW is unique among soil water models for the following features: (1) it can be used to simulate with varying topography; (2) it determines 3-D flows from drains in a heterogeneous, anisotropic soil; (3) it presents results in tabular format, contour map format, or 3-D surface format; and (4) it contains software routines for automated control in subirrigation. The formation of the conceptual model, numerical relations, methods of solution, validation, field verification and examples are presented.
31
Marinuzzi, Natalie Romina. "LOCATION OF SINKHOLE CONFINING BREACH USING GROUNDWATER FLOW PATTERNS DERIVED FROM CONE PENETRATION TESTING". Master's thesis, University of Central Florida, 2004. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4442.
Testo completoAbstract (sommario):
Dynamic forces in the hydrologic cycle move underground water through Florida's carbonate rocks dissolving chemical components of the rocks, leaving behind caves, solution pipes, and other voids that result in a karst terrain. Ravelling is the common subsidence mechanism throughout most of Florida where unconsolidated materials filter downward into voids in the underlying limestone. A cavity in the overburden develops and enlarges over a period of many years. The enlarged cavity is also known as sinkhole. The investigations of sinkhole characteristics and potential involve studying the regional geology, hydrology and mapping historic sinkholes that have occurred in the area. Use of Cone Penetration Test (CPT) soundings, in conjunction with conventional soil borings are becoming more common in the assessment of subsurface soil conditions in the vicinity of sinkhole-related ground surface. The penetration resistance data by CPT can determine the presence and extent of raveled soil zones characteristic of sinkhole features, and the penetration pore water pressure data can be used to determine the integrity of the clay confining unit at each test sounding location. The objective of this study is to identify the possible location of the confining breach at a sinkhole in Seminole County. The methods used in the assessment of the sinkhole's subsurface conditions were Standard Penetration Test (SPT), which provided information that helped to identify the location of the ravelled zones within the soil profile, and Cone Penetration Test that gave information of the piezometric water levels obtained from the pore pressure dissipation curves. The total head was calculated from the piezometric water levels corresponding to the different elevations. The data were found to exhibit a downward behavior of the total head, starting at around elevation 50 feet, NGVD that extended towards lower elevations. The SPT boring log identified a ravelled zone starting at 31 feet approximately. From both information it was possible to establish that the hydraulic head was influenced by the proximity of the ravelled zones, where the head precipitated rapidly as the elevation decreased. From the result of this study, it was concluded that the location of the breach in the confining layer started at 61.8 feet deep below the ground surface. Potentiometric contour lines at elevation 24.40 feet denoted flow patterns of water from the surroundings of the depression towards the approximate location of the center, which is the existing of subsurface cavity.M.S.
Department of Civil and Environmental Engineering
Engineering and Computer Science
Civil and Environmental Engineering
32
Safaei, Jazi Ramin. "Simulation of Groundwater Flow System in Sand- Lick Watershed, Boone County, West Virginia (Numerical Modeling Approach)". Thesis, Kent State University, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=1555300.
Testo completoAbstract (sommario):
Determining the hydraulic properties of aquifer and aquitards (K,T,and S) is very important in hydrogeologic studies. These parameters can be identified by methods such as laboratory permeability and borehole hydraulic response test. Because these approaches are sometimes costly, involving drilling test holes, and often may not be feasible, numerical modeling approaches can be considered as alternatives. In the following study, numerical modeling is applied to simulate groundwater flow system to determine the hydraulic properties of a weathered/fractured zone in a valley located within the Appalachian Plateau Geomorphic Province. The Appalachian Plateau is characterized by relatively flat-laying but intensely eroded bedrock, comprising cyclical sequences of Pennsylvanian age sedimentary bedrock dominated by sandstone, siltstone, shale, coal, claystone, and occasionally limestone. Fractured/weathered sandstone is potentially the main bedrock groundwater transmitting formation. The extent of fractures is from the ground surface to about 120-150 ft (or roughly 30-40m) under the ground surface. The main groundwater flow occurs from within the intergranular pore space through fractures and along bedding planes of the bedrock.
The water level at a perennial stream in the valley can be considered as the phreatic ground-water level. Therefore, the elevation points along this stream may serve as model calibration points. Because the outflow from the valley is almost entirely via the creek, and creek water represents the groundwater level all along the valley, the model is calibrated and verified by the creek water elevations and the amount of water discharging through the valley. The site- specific hydrogeologic interpretation and evaluation technique presented in this study may be very well applicable to the significant portions of the Allegheny Plateau with similar geomorphologic, tectonic and lithologic characteristics.
33
Safaei, Jazi Ramin. "Simulation of Groundwater Flow System in Sand-Lick Watershed, Boone County, West Virginia (Numerical Modeling Approach)". Kent State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=kent1375983541.
Testo completo
34
Weeden, A. Curtis Jr. "Simulation of Groundwater Flow in the Rincon Valley Area and Mesilla Basin, New Mexico and Texas". Thesis, The University of Arizona, 1999. http://hdl.handle.net/10150/191359.
Testo completoAbstract (sommario):
A groundwater flow model was constructed for the Rincon Valley area and Mesilla Basin. The system is dominated by the complex interaction of the Rio Grande, canals, laterals, and drains. The primary purposes of the model were to assess the effect of municipal and industrial pumping on the Rio Grande and to evaluate the effect of nonirrigation releases from Caballo Reservoir on the water budget. In addition, the model will eventually be linked to a surface water model (BESTSM) being utilized to evaluate water supply alternatives for El Paso, Texas. Stress periods were specified on a seasonal basis, an irrigation season from March through October and a non-irrigation season from November through February. Analysis of model output indicates that pumping may decrease Rio Grande flows, non-irrigation season releases do not alter the water budget significantly, and that recharge and discharge from aquifer storage are strongly related to the season.
35
Yu, Tungsheng. "Traffic flow modeling in highway networks". Master's thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-12232009-020154/.
Testo completo
36
Qin, H. Q. "Computer and water-model simulation of flow through poppet valves". Thesis, Imperial College London, 1985. http://hdl.handle.net/10044/1/37825.
Testo completo
37
Wang, Xu. "Freeway exit ramp traffic flow research based on computer simulation". [Tampa, Fla] : University of South Florida, 2008. http://purl.fcla.edu/usf/dc/et/SFE0002332.
Testo completo
38
Wang, Xu. "Freeway Exit Ramp Traffic Flow Research Based on Computer Simulation". Scholar Commons, 2007. https://scholarcommons.usf.edu/etd/554.
Testo completoAbstract (sommario):
Interstate highways are one of the most important components of the transportation infrastructure in America. Freeway ramps play an important role in the whole interstate transportation system.
This paper researches the traffic flow characteristics of four typical exit ramps in USA, which are tapered one-lane exit, tapered two-lane exit, parallel one-lane exit and parallel two-lane exit. Computer simulation software, such as CORSIM and HCS are applied as the main tools in this research. ANOVA and Tukey are used for statistical purpose.
It compares the maximum capacity, average running speed and the total lane change number of those four exit ramps. It is found that no matter in terms of traffic discharging rate or total lane charging number; the tapered two-lane exit has the best operational performance. Tapered one-lane exit ramp has the least capacity.
Parallel one-lane exit and parallel two-lane exit have very limited traffic operational difference in terms of capacity and running speed. It is recommended that parallel two-lane exit ramp should not be designed along the freeway if the right of way along arterial road is enough.
It is observed from the simulation data that the grade of freeway, truck percentage, restricted to the truck use of certain lane(s) and the location of exit sign have significant impact on the running speed and total lane change number. An uphill can decrease the running speed dramatically while more truck brings more lane change, causing safety concerns.
It is found that when trucks are restricted to the right two most lane, there will be less lane change number comparing with trucks are not restricted.
Location of exit sign operates well at the distance between 4000 ft to 5000 ft. does have a significant impact on the operational speed and total lane change number before, within or after functional area of an exit, based on the data analysis of simulation runs.
39
Reasor, Daniel Archer. "Numerical simulation of cellular blood flow". Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/42760.
Testo completoAbstract (sommario):
In order to simulate cellular blood, a coarse-grained spectrin-link (SL) red blood cell (RBC) membrane model is coupled with a lattice-Boltzmann (LB) based suspension solver. The LB method resolves the hydrodynamics governed by the Navier--Stokes equations while the SL method accurately models the deformation of RBCs under numerous configurations. This method has been parallelized using Message Passing Interface (MPI) protocols for the simulation of dense suspensions of RBCs characteristic of whole blood on world-class computing resources.
Simulations were performed to study rheological effects in unbounded shear using the Lees-Edwards boundary condition with good agreement with rotational viscometer results from literature. The particle-phase normal-stress tensor was analyzed and demonstrated a change in sign of the particle-phase pressure from low to high shear rates due to RBCs transitioning from a compressive state to a tensile state in the flow direction. Non-Newtonian effects such as viscosity shear thinning were observed for shear rates ranging from 14-440 inverse seconds as well as the strong dependence on hematocrit at low shear rates. An increase in membrane bending energy was shown to be an important factor for determining the average orientation of RBCs, which ultimately affects the suspension viscosity. The shear stress on platelets was observed to be higher than the average shear stress in blood, which emphasizes the importance of modeling platelets as finite particles.
Hagen-Poiseuille flow simulations were performed in rigid vessels for investigating the change in cell-depleted layer thickness with shear rate, the Fåhraeus-Linqvist effect, and the process of platelet margination. The process of platelet margination was shown to be sensitive to platelet shape. Specifically, it is shown that lower aspect ratio particles migrate more rapidly than thin disks. Margination rate is shown to increase with hematocrit, due to the larger number of RBC-platelet interactions, and with the increase in suspending fluid viscosity.
40
Isikli, Yeliz. "Modeling Groundwater Flow In A Raw Material Site Of A Cement Factory,kocaeli-darica,turkey". Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/1219849/index.pdf.
Testo completoAbstract (sommario):
An areal numerical simulation has been carried out to investigate effects of
below-sea-level (BSL) excavation in the raw material site of a cement factory in
Turkey. A finite element model (585 nodes with 534 elements) is formed to solve
for the head distribution in the quarry site upon quarry operation planned to be
implemented in the near future. The model is calibrated to the field conditions and
appropriate boundary conditions and the physical parameters are obtained to be
used in future prediction studies.
After a successful calibration the model is run to estimate the water levels and the
discharge rates required during below sea level quarry operations.
Above sea level (ASL) and below sea level (BSL) operations are simulated and
water level contour maps are obtained both for above sea level (ASL) production
for the 2000-2030 period, and for each BSL (-10m, -20m, -30m) production
periods, which would totally take 13 years.
Estimation show that the proposed model runs properly and it calculates the water
levels and discharge rates accurately for probable future quarry operations. It is
clear that quarry operations would not create a serious problem in terms of water
discharge from the quarry site.
41
McCallum, Marcus Anthony. "The simulation of wet steam flow in a turbine". Thesis, University of Strathclyde, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366697.
Testo completo
42
Floros, Nikolaos. "An incompressible flow simulation environment for parallel and distributed computers". Thesis, University of Southampton, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241983.
Testo completo
43
Zhang, Keni. "The modal reduction method for simulation of groundwater flow and multi-species contaminant transport in fractured porous media". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0026/NQ51676.pdf.
Testo completo
44
Demirci, Turan. "Federated Simulation Of Network Performance Using Packet Flow Modeling". Phd thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/2/12611704/index.pdf.
Testo completoAbstract (sommario):
Federated approach for the distributed simulation of a network, is an alternative method that aims to combine existing simulation models and software together using a Run Time Infrastructure (RTI), rather than building the whole simulation from scratch. In this study, an approach that significantly reduces the inter-federate communication load in federated simulation of communication networks is proposed. Rather than communicating packet-level information among federates, characteristics of packet flows in individual federates are dynamically identified and communicated. Flow characterization is done with the Gaussian Mixtures Algorithm (GMA) using a Self Organizing Mixture Network (SOMN) technique. In simulations of a network partitioned into eight federates in space parallel manner, it is shown that significant speedups are achieved with the proposed approach without unduly compromising accuracy.
45
Wise, John Nathaniel. "Inverse modelling and optimisation in numerical groundwater flow models using proper orthogonal decomposition". Thesis, Saint-Etienne, EMSE, 2015. http://www.theses.fr/2015EMSE0773/document.
Testo completoAbstract (sommario):
Des simulateurs numériques sont couramment utilisés pour la prédiction et l'optimisation de l'exploitation d'aquifères et pour la détermination de paramètres physiques (e.g perméabilité) par calcul inverse. L'équation de Richards, décrit l'écoulement d'un fluide dans un milieu poreux non saturé. C'est une équation aux dérivées partielles non linéaires, dont la résolution numérique en grande dimension 3D est très coûteuse et en particulier pour du calcul inverse.Dans ce travail, une méthode de réduction de modèle (ROM) est proposée par une décomposition orthogonale propre (POD) afin de réduire significativement le temps de calcul, tout maîtrisant la précision. Une stratégie de cette méthode est de remplacer localement dans l'algorithme d'optimisation, le modèle fin par un modèle réduit type POD. La méthode de Petroc-Galerkin POD est d'abord appliquée à l'équation de Richards et testée sur différents cas, puis adaptée en linéarisant les termes non linéaires. Cette adaptation ne fait pas appel à une technique d'interpolation et réduit le temps de calcul d'un facteur [10;100]. Bien qu'elle ajoute de la complexité du ROM, cette méthode évite d'avoir à ajuster les paramètres du noyau, comme c'est le cas dans les méthodes du POD par interpolation. Une exploration des propriétés d'interpolation et d'extrapolation inhérentes aux méthodes intrusives est ensuite faite. Des qualités d'extrapolation intéressantes permettent de développer une méthode d'optimisation nécessitant de petits plans d'expériences (DOE). La méthode d'optimisation recrée localement des modèles précis sur l'espace des paramètres, en utilisant une classification à vecteurs de support non linéaire pour délimiter la zone où le modèle est suffisamment précis, la région de confiance. Les méthodes sont appliquées sur un cas d'école en milieu non saturé régit par l'équation de Richards, ainsi que sur un aquifère situé dans le "Table Mountain Group" près de la ville du Cap en Afrique du SudThe Richards equation describes the movement of an unsaturated fluid through a porous media, and is characterised as a non-linear partial differential equation. The equation is subject to a number of parameters and is typically computationnaly expensive to solve. To determine the parameters in the Richards equation, inverse modelling studies often need to be undertaken. As a solution to overcome the computational expense incurred in inverse modelling, the use of Proper Orthogonal Decomposition (POD) as a Reduced Order Modelling (ROM) method is proposed in this thesis to speed-up individual simulations. The Petrov-Galerkin POD approach is initially applied to the Richards equation and tested on different case studies. However, due to the non-linear nature of the Richards equation the method does not result in significant speed up times. Subsquently, the Petrov-Galerkin method is adapted by linearising the nonlinear terms in the equation, resulting in speed-up times in the range of [10,100]., The adaptation, notably, does not use any interpolation techniques, favouring an intrusive, but physics-based, approach. While the use of intrusive POD approaches add to the complexity of the ROM, it avoids the problem of finding kernel parameters typically present in interpolative POD approaches. Furthermore, the interpolative and possible extrapolation properties inherent to intrusive PODROM's are explored. The good extrapolation propertie, within predetermined bounds, of intrusive POD's allows for the development of an optimisation approach requiring a very small Design of Experiments (DOE). The optimisation method creates locally accurate models within the parameters space usign Support Vector Classification. The limits of the locally accurate model are called the confidence region. The methods are demonstrated on a hypothetical unsaturated case study requiring the Richards equation, and on true case study in the Table Mountain Group near Cape Town, South Africa
46
Maddock, Thomas III, e Laurel J. Lacher. "MODRSP: a program to calculate drawdown, velocity, storage and capture response functions for multi-aquifer systems". Department of Hydrology and Water Resources, University of Arizona (Tucson, AZ), 1991. http://hdl.handle.net/10150/620142.
Testo completoAbstract (sommario):
MODRSP is program used for calculating drawdown, velocity, storage losses and
capture response functions for multi - aquifer ground -water flow systems. Capture is
defined as the sum of the increase in aquifer recharge and decrease in aquifer discharge
as a result of an applied stress from pumping [Bredehoeft et al., 19821. The capture
phenomena treated by MODRSP are stream- aquifer leakance, reduction of
evapotranspiration losses, leakance from adjacent aquifers, flows to and from prescribed
head boundaries and increases or decreases in natural recharge or discharge from head
dependent boundaries.
The response functions are independent of the magnitude of the stresses and are
dependent on the type of partial differential equation, the boundary and initial
conditions and the parameters thereof, and the spatial and temporal location of stresses.
The aquifers modeled may have irregular -shaped areal boundaries and non -homogeneous
transmissive and storage qualities. For regional aquifers, the stresses are generally
pumpages from wells. The utility of response functions arises from their capacity to be embedded in
management models. The management models consist of a mathematical expression of
a criterion to measure preference, and sets of constraints which act to limit the
preferred actions. The response functions are incorporated into constraints that couple
the hydrologic system with the management system (Maddock, 1972). MODRSP is a modification of MODFLOW (McDonald and Harbaugh, 1984,1988). MODRSP uses many of the data input structures of MODFLOW, but there are major differences between the two programs. The differences are discussed in Chapters
4 and 5. An abbreviated theoretical development is presented in Chapter 2, a more
complete theoretical development may be found in Maddock and Lacher (1991). The
finite difference technique discussion presented in Chapter 3 is a synopsis of that
covered more completely in McDonald and Harbaugh (1988). Subprogram organization
is presented in Chapter 4 with the data requirements explained in Chapter 5. Chapter
6 contains three example applications of MODRSP.
47
薛明輝 e Ming-fai Sit. "Computation of stratified flow past three dimensional surface mounted obstacles". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1988. http://hub.hku.hk/bib/B31208897.
Testo completo
48
Clemente, Roberto Sulit. "A mathematical model for simulating pesticide fate and dynamics in the environment (PESTFADE) /". Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=70275.
Testo completoAbstract (sommario):
A one-dimensional transient mathematical model which can predict simultaneous movement of water and reactive solutes through homogeneous soil systems under saturated/unsaturated conditions is developed. The physically-based numerical model, called PESTFADE, considers the interactive processes/mechanisms such as mass flow, plant uptake, adsorption/desorption, dispersion, volatilization, chemical/microbial degradation and runoff in the simulation.The PESTFADE model employs SWACROP, a model developed in the Netherlands, to simulate transient water flow in the unsaturated zone; evaluates non-equilibrium sorption in macropores, analyzes soil heat flow to to model microbial degradation, calculates pesticide partitioning in runoff/sediment as affected by agricultural management practices, and describes first order degradation and sorption kinetics. The governing partial differential equation describing the various processes is solved numerically via the Numerical Method of Lines (NMOL) technique, and the computer programs are written in FORTRAN 77. The resulting computer code (PESTFADE), is run on a microcomputer and has been implemented for interactive simulation on IBM PC or compatible microcomputers.
The model was tested and validated using actual data measured from field plot experiments involving herbicide atrazine which was post-emergently applied in a corn field on a loam soil. Various analytical solutions were used to check the accuracy of the different components of PESTFADE, and parametric sensitivity analyses were performed to determine how the model output reacts to changes in some selected input parameters.
Results indicate that model predictions generally agreed with measured concentrations of atrazine and compared closely with the analytical solutions. Moreover, model performance tests showed that predicted values are within acceptable ranges of model accuracy and bound of experimental uncertainties. It was also found that the model is very sensitive to degradation rate constant (k), sorption coefficient (K$ sb{ rm d})$ and soil temperature and slightly sensitive to management practice (CN) and sorption site fraction (F). Finally, the various field scenarios and pathways for non-point source contamination evaluated in the study have demonstrated the wide applicability and flexibility of PESTFADE.
49
Dean, William T. "A computer simulation model of fluid flow through a channel with constriction". Monterey, California: Naval Postgraduate School, 2013. http://hdl.handle.net/10945/34654.
Testo completoAbstract (sommario):
Approved for public release; distribution is unlimitedComputer simulation is a valuable tool for the research of physics. These simulations can be especially valuable when there is experimental data available that can be used to validate the model. The main objective of this thesis is to determine whether a computer simulation model can accurately depict the experimentally determined fluid flow for a channel with a series of unique individual constrictions. The experimental data are derived from a scaled-up model of coronary blood flow with localized axisymmetric constrictions (or stenoses), representing an ideal case of atherosclerotic disease. This thesis provides the foundation for future study and simulation to develop a microelectromechanical device mounted on a stent capable of sensing and transmitting changes in blood flow characteristics and properties to an outside receiver for improved treatment of patients with atherosclerotic coronary artery disease.
50
Shojae, Ghias Masoumeh. "Numerical simulations of coupled groundwater flow and heat transport incorporating freeze/thaw cycles and phase change in a continuous permafrost environment". Doctoral thesis, Université Laval, 2017. http://hdl.handle.net/20.500.11794/27693.
Testo completoAbstract (sommario):
Dans les régions nordiques, l’une des conséquences du réchauffement climatique est le dégel du pergélisol. En plus de favoriser la libération de quantités importantes de méthane et de dioxyde de carbone dans l’atmosphère, le dégel du pergélisol entraînera une modification des conditions hydrologiques locales et régionales, affectant ainsi les écosystèmes. Ce dégel pourra aussi conduire à un affaissement des sols et endommager ainsi les infrastructures routières. Dans le cadre de cette étude, des simulations numériques couplant l’écoulement des eaux souterraines et le transport de chaleur ont été réalisées dans le but de mieux appréhender les interactions entre l’écoulement des eaux souterraines et la dynamique thermique relative au dégel du pergélisol sur les pistes de l’Aéroport d’Iqaluit, Nunavut, Canada. Un modèle conceptuel du site est d’abord développé et le modèle numérique bidimensionnel correspondant est calé à partir des températures observées du sol. Les impacts futurs du réchauffement climatique sur le régime thermique et le système d’écoulement, aussi que le tassement dû au dégel, sont ensuite simulés sur la base des scénarios climatiques proposés par le Groupe Intergouvernemental sur l’Évolution du Climat (GIEC). Dans le cadre d’un réchauffement climatique, la couverture neigeuse de surface est identifiée comme le facteur principal affectant la dégradation du pergélisol, y compris par son rôle dans l’accroissement de la sensibilité de la dégradation du pergélisol aux changements de divers facteurs hydrogéologiques. Dans ce cas, le transfert de chaleur par advection joue un rôle relativement mineur, quoique non négligeable, vis-à-vis du transfert de chaleur par conduction, du fait de l’extension importante d’un sol de faible perméabilité à proximité de la surface. Le transfert de chaleur par convection, qui est fortement influencé par la couche de neige superficielle, contrôle la libération de l’eau non gelée et la profondeur de la couche active aussi bien que l’amplitude du tassement et du soulèvement par le dégel. L'effet de la zone non saturée sur le dégel du pergélisol est plus important dans les sols fins, recouverts de neige en surface. De plus, l’ampleur du tassement dû au dégel augmente considérablement en présence d’une couverture neigeuse. Enfin, les simulations ont montré que, le long de routes, les zones les plus vulnérables au tassement sont les accotements recouverts de neige ainsi que les zones de transition adjacentes au bloc de pergélisol. Les simulations numériques ont également montré l’importance d’utiliser les fonctions de gel appropriées pour les types de sols impliqués. En effet, la position du front de gel (couche active) varie en fonction des caractéristiques du sol. Les résultats des simulations ont également mis en évidence les effets d'une distribution stochastique de la conductivité hydraulique sur l’advection thermique. Les taux de dégel du pergélisol sont relativement plus élevés dans des zones de haute perméabilité, trouvées dans la structure du sol d'un système hétérogène, que dans le cas d’un sol homogène. Paradoxalement, les résultats ont montré que dans les zones de décharge, le transport de chaleur par advection a pour conséquence d'augmenter le plafond du pergélisol. En effet, l'eau froide s'écoulant dans ce secteur annule le gain de chaleur résultant du processus de conduction.At high northern latitudes, climate warming will induce permafrost degradation that will modify local and regional hydrogeological systems and ecosystem functionality, as well as increase the release of carbon and methane to the environment. Northern infrastructure, in particular roads and embankments, will also experience significant degradation. In this study, numerical simulations of coupled groundwater flow and heat transport have been developed to assess the effects of realistic combinations of hydrogeological parameters and surface conditions on the temporal and spatial evolution of permafrost degradation in a cold-region paved terrain, at the Iqaluit airport, Nunavut. A conceptual model is first developed for the site and a corresponding 2D numerical model is calibrated to the observed groundwater flow and thermal regime. Future climate warming impacts on the thermal regime and flow system, as well as thaw settlements are then simulated based on climate scenarios proposed by the IPCC (Intergovernmental Panel on Climate Change). Under climate warming, the surface snow cover is identified as the leading factor affecting permafrost degradation, and significantly contributes to positive feedback between the hydrogeological flow system and the frozen ground. In this case, advective heat transport plays a relatively minor, but non-negligible role compared to conductive heat transport, due to the significant extent of low-permeability soil close to surface. Conductive heat transport, which is strongly affected by the surface snow layer, controls the release of unfrozen water and the depth of the active layer as well as the magnitude of thaw settlement and frost heave. The effect of the unsaturated zone on permafrost thaw was most important in finer soil where overlain by snow. The magnitude of thaw settlement also significantly increases with a snow cover. The most vulnerable areas to permafrost thaw settlement along a road or taxiway embankment would be the snow-covered shoulders, as well as the transition zones at the adjacent margins of the permafrost block. The simulation results also showed the importance of selecting the appropriate freezing function based on the type of soil, when frequent freezing and thawing cycles occur in a permafrost setting. The thaw front simulated with a smooth (low slope) freezing function, was deeper compared to that for a steeper freezing function. The simulation results also highlighted the contributing effects of a stochastic hydraulic conductivity distribution on thermal advection. Permafrost thaw rates in high permeability zones, found in the soil structure of a heterogeneous system, are larger than rates for a homogeneous soil. Advective heat transport can paradoxically also increase the permafrost table in downgradient areas where the flowing cold water negates heat gain from conduction alone.