Дисертації з теми "Hydrodynamic and biokinetic modeling"
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1
Vink, J. S. "Discussion: Hydrodynamic modeling." Universität Potsdam, 2007. http://opus.kobv.de/ubp/volltexte/2008/1804/.
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2
Nzokou, Tanekou François. "Ice rupture hydrodynamic modeling." Thesis, Université Laval, 2010. http://www.theses.ulaval.ca/2010/26683/26683.pdf.
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3
Marchand, Philippe. "Hydrodynamic modeling of shallow basins." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0003/MQ44218.pdf.
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Marchand, Philippe 1972. "Hydrodynamic modeling of shallow basins." Thesis, McGill University, 1997. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=20274.
Повний текст джерелаАнотація:
A two-dimensional hydrodynamic model is used to simulate the flow field and the concentration distribution of a conservative tracer in shallow basins. A series of numerical test are performed to evaluate different numerical schemes and problems which arise for the use of the Second Moment Method (SMM) in diffusion dominated flows are reported. The results of the basin simulations are compared with experimental data. The model predicts the location and the size of the dead zones, bypassing, recirculation, and local concentrations within the basin. The positioning of the inlet and outlet, and the presence of baffles are important parameters for the location and size of dead zones. The model gives results which are in agreement with the experimental data. The results show that the hydrodynamic model is quite powerful in terms of predicting correctly the residence time distribution for ponds of various dimensions and shapes.
5
Meakin, Casey Adam. "Hydrodynamic Modeling of Massive Star Interiors." Diss., The University of Arizona, 2006. http://hdl.handle.net/10150/194035.
Повний текст джерелаАнотація:
In this thesis, the hydrodynamics of massive star interiors are explored. Our primary theoretical tool is multi-dimensional hydrodynamic simulation using realistic initial conditions calculated with the one-dimensional stellar evolution code, TYCHO. The convective shells accompanying oxygen and carbon burning are examined, including models with single as well as multiple, simultaneously burning shells. A convective core during hydrogen burning is also studied in order to test the generality of the flow characteristics. Two and three dimensional models are calculated. We analyze the properties of turbulent convection, the generation of internal waves in stably stratified layers, and the rate and character of compositional mixing at convective boundaries.
6
Sherburn, Jesse Andrew. "HYDRODYNAMIC MODELING OF IMPACT CRATERS IN ICE." MSSTATE, 2008. http://sun.library.msstate.edu/ETD-db/theses/available/etd-11052007-091023/.
Повний текст джерелаАнотація:
In this study, impact craters in water ice are modeled using the hydrodynamic code CTH. In order to capture impact craters in ice an equation of state and a material model are created and validated. The validation of the material model required simulating the Split Pressure Hopkinson Bar (SPHB) experimental apparatus. The SPHB simulation was first compared to experiments completed on Al 6061-T6, then the ice material model was validated. After validation, the cratering simulations modeled known experiments found in the literature. The cratering simulations captured the bulk physical aspects of the experimental craters, and the differences are described. Analysis of the crater simulations showed the damaged volume produced by the projectile was proportional to the projectiles momentum. Also, the identification of four different stages in the crater development of ice (contact and compression, initial damage progression, crater shaping, and ejected damaged material) are described.
7
Luca, Liliana. "Hydrodynamic modeling of electron transport in graphene." Doctoral thesis, Università di Catania, 2019. http://hdl.handle.net/10761/4103.
Повний текст джерелаАнотація:
Semi-classical hydrodynamic models for charge transport in graphene have been presented. They are deduced as moment equations of the semiclassical Boltzmann equation with the needed closure relations obtained by resorting to the Maximum Entropy Principle. The models differ in the choice of the moments to assume as basic field variables. Both linear and nonlinear closure relations are analyzed. The validity of all the semi-classical models presented is assessed by comparing the mean values of energy and velocity with those obtained from the direct solutions of the Boltzmann equation in the simple case of suspended monolayer graphene. It has been found that it is crucial to include- among the field variables- the deviatoric part of the stress tensor to maintain a good accuracy in a wider range of applied electric fields. Moreover apparently the results confirm that the nonlinearity is not critical for accuracy.
Then, to take into account quantum phenomena, in the last part of this work a quantum hydrodynamic model for charge transport in graphene is derived from a moment expansion of the Wigner-Boltzmann equation. The needed closure relations are obtained by adding to the semiclassical ones quantum corrections based on the equilibrium Wigner function. The latter is obtained from the Bloch equation by taking into account the appropriate energy band of graphene. Furthermore, quantum energy-transport and drift-diffusion models have been formally derived from the quantum hydrodynamic equations in the long time asymptotic limit. In analogy with the semiclassical case we are confident that the energy-transport and drift-diffusion models have mathematical properties which allow an easier numerical treatment.
8
Eriksson, Jonas. "Evaluation of SPH for hydrodynamic modeling,using DualSPHysics." Thesis, Uppsala universitet, Avdelningen för beräkningsvetenskap, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-339557.
Повний текст джерелаАнотація:
Computational methods are always being invented, improved and adjusted to newkinds of problems, this is a constant process happening all the time. The studyevaluates a method called Smoothed Particle Hydrodynamics (SPH) for modelingon fluid flows around ship hulls. This has been done mainly using a open sourcecode called DualSPHysics. The SPH method has been applied to complex problemsas well as simple problems for comparison to well known phenomena. It is aearly study of the method and aimed at discovering how to proceed when studyingthe method in the future. The results seem promising especially when computationsare made using Graphics Processing Units (GPU) for calculations. The codeDualSPHysics used in the study shows promise but might be in need of some morefunctions before being practically applicable for simulation of ship hulls.
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Esmond, Micah Jeshurun. "Two-dimensional, Hydrodynamic Modeling of Electrothermal Plasma Discharges." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/81447.
Повний текст джерелаАнотація:
A two-dimensional, time-dependent model and code have been developed to model electrothermal (ET) plasma discharges. ET plasma discharges are capillary discharges that draw tens of kA of electric current. The current heats the plasma, and the plasma radiates energy to the capillary walls. The capillary walls ablate by melting and vaporizing and by sublimation. The newly developed model and code is called the Three-fluid, 2D Electrothermal Plasma Flow Simulator (THOR). THOR simulates the electron, ion, and neutral species as separate fluids coupled through interaction terms. The two-dimensional modeling capabilities made available in this new code represent a tool for the exploration and analysis of the physics involved in ET plasma discharges that has never before been available.
Previous simulation models of ET plasma discharges have relied primarily on a 1D description of the plasma. These models have often had to include a tunable correction factor to account for the vapor shield layer - a layer of cold ablated vapor separating the plasma core from the ablating surface and limiting the radiation heat flux to the capillary wall. Some studies have incorporated a 2D description of the plasma boundary layer and shown that the effects of a vapor shield layer can be modeled using this 2D description. However, these 2D modeling abilities have not been extended to the simulation of pulsed ET plasma discharges. The development of a fully-2D and time-dependent simulation model of an entire ET plasma source has enabled the investigation of the 2D development of the vapor shield layer and direct comparison with experiments. In addition, this model has provided novel insight into the inherently 2D nature of the internal flow characteristics involved within the plasma channel in an ET plasma discharge. The model is also able to capture the effects of inter-species interactions.
This work focuses on the development of the THOR model. The model has been implemented using C++ and takes advantage of modern supercomputing resources. The THOR model couples the 2D hydrodynamics and the interactions of the plasma species through joule heating, ionization, recombination, and elastic collisions. The analysis of simulation results focuses on emergent internal flow characteristics, direct simulation of the vapor shield layer, and the investigation of source geometry effects on simulated plasma parameters. The effect of elastic collisions between electrons and heavy species are shown to affect internal flow characteristics and cause the development of back-flow inside the ET plasma source. The development of the vapor shield layer has been captured using the diffusion approximation for radiation heat transfer within the ET plasma source with simulated results matching experimental measurements. The relationship between source radius and peak current density inside ET plasma discharges has also been explored, and the transition away from the ablation-controlled operation of ET plasma discharges has been observed.Ph. D.
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MEGGIOLARO, MARCO ANTONIO. "HYDRODYNAMIC BEARING MODELING FOR THE SIMULATION OF ROTATING SYSTEMS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1996. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=19287@1.
Повний текст джерелаАнотація:
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICONeste trabalho a análise do comportamento de sistemas rotativos do tipo eixo-rotormancal é estendida para incluir os efeitos da presença de mancais hidrodinâmicos na resposta dinâmica. Estes efeitos estão associados à não-linearidade da força de reação exercida pelos suportes sobre o eixo e dependem dos deslocamentos, velocidades transversais e da rotação própia do rotor. A modelagem estrutural do sistema é obtida empregando-se o método dos elementos finitos. O eixo é representado pelo modelo de viga de Timoshenko com dois nós, quatro graus-de-liberdade por nó, e a interpolação do campo de deslocamentos é obtida utilizando-se as funções de Hermite. Os rotores são modelados empregando-se elementos de inércia concentrada associada aos graus-de-liberdade de um ponto nodal do modelo. E, na representação dos mancais hidrodinâmicos utilizou-se a equação de Reynolds, com as hipóteses simplificadoras para mancais curtos, obtendo-se a solução para a distribuição de pressão do filme de óleo em forma fechada. Essa distribuição de pressão permite a obtenção dos coeficientes das matrizes e rigidez e de amortecimento associadas aos graus de liberdade do eixo no ponto nodal de representação do mancal. Para a integração temporal do sistema de equações diferencias utiliza-se o procedimento passo-a-passo, tendo-se implementado os métodos implícitos de Newmark e Wilson – teta, na forma incondicionalmente estável. Devido à não-linearidade das equações obtidas com a presença dos mancais hidrodinâmicos, em cada intervalo de tempo utiliza-se o procedimento de Newton-Raphson modificado para a correção da solução numérica obtida com outros resultados analíticos/numéricos disponíveis na literatura. Também, uma representação numérica para mancais hidrodinâmicos segmentados é apresentada, utilizando-se o desenvolvimento teórico para mancais simples. Neste caso a avaliação do procedimento numérico é fornecida comparando-se a solução numérica com resultados experimentais obtidos dos rotores de usina hidrogenada avaliada pelo CEPEL. Em ambos os procedimentos o rotor idealizado de jeffcott é empregado no estudo de casos. Verifica-se que os principais resultados associados aos efeitos da precessão auto-excitada (oil whirl), de chicoteamento (oil whip), e da estabilização dinâmica do sistema são reproduzidos pelos modelos numéricos utilizados.
In this work a formulation for the analysis of shaft-rotor-bearing type rotating systems is extendend to accommodate the effects of hydrodynamic bearings in its dynamic response. These effects, which are associated to the nonlinear force on the shaft at the bearings, are dependent of the transverse displacements, transverse linear velocities an the angular veolicty of the shaft. The structure behavior is modeled by employing the finite element method. The shaft is represented by the two node timoshenko model for bearns, with four desgrees-of-freedom per node and Hermite interpolation functions to represent the displacement fields along the bearn axis. Rotors are modeled by using concentrated inertia elements associated to the shaft degrees-of-freedom at the bearing nodal point. In the numerical analysis considering the time integration of the system differential equation, a step-by-step procedure was employed with the newmark technique in this unconditionally stable form. Due to the nonlearities associated with the hydrodynamic bearings, the solution of the system of equations is obtained using a modified Newton-Raphson precedure at each time step for solution convergence. In the evaluation of the proposed computacional system, comparison with solutions obtained from analytical/numerical results available in the literature are used. Also, a numeric represemtation of tilting-pad bearings is presented using the theory for plain journal bearings, under the same simplified conditions. In this case an evaluation of the numerical procedure is given by comparing calculated solutions with experimental results obtained from the evaluation of a hydrogenaration plant provided by CEPEL-Brazilian Research Center For Eletrobras. In both plain an tilting-pad journal bearing numerical procedures, the idealized Jeffcott rotor is employed as a case study for different operating conditions. As a result, it is shown that the solutions associated to the main oil whirl and oil whip effects and afterwards dynamic stabilization are represented by the proposed numerical procedures employed.
11
Luttrell, Gerald H. "Hydrodynamic studies and mathematical modeling of fine coal flotation." Diss., Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/49828.
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12
Geiger, Sam R. "Hydrodynamic modeling of towed buoyant submarine antenna's in multidirectional seas." Thesis, Springfield, Va. : Available from National Technical Information Service, 2000. http://handle.dtic.mil/100.2/ADA383464.
Повний текст джерелаАнотація:
Thesis (M.S. in Oceanographic Engineering) Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution, Sept. 2000.Includes bibliographical references (p. 100-101). Also available online.
13
Zuloaga, Jorge. "Hydrodynamic Modeling of Dielectric Response in Graphene and Carbon Nanotubes." Thesis, University of Waterloo, 2006. http://hdl.handle.net/10012/1113.
Повний текст джерелаАнотація:
This thesis studies two important carbon structures, graphene and carbon nanotubes, with the purpose of understanding how their three-dimensional electron density distribution affects the way fast ions interact with them. A brief introduction to research in pure carbon structures is made. We then use different models to calculate the equilibrium electron density distribution in graphene and carbon nanotubes.
In the second part of the thesis we investigate fast ions moving parallel to a graphene sheet and experiencing forces due to the dynamic polarization of carbon valence electrons. Using the three-dimensional electron density distribution of graphene, we calculate the force directly opposing the ion's motion (stopping force), as well as the force which bends the ion's trajectory towards the sheet (image force). It is our purpose to compare these results with those based on a two-dimensional hydrodynamic model of graphene, which approximates the electron distribution of graphene by a charged fluid confined to the two-dimensional plane of the sheet.
The results obtained for interactions of ions with a single graphene sheet should be useful for a further analysis of ion channeling through carbon nanostructures.
14
Philipp, Andy. "Novel Analytical Hydrodynamic Modeling for Evaluating and Optimizing Alluvial Recharge." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-124891.
Повний текст джерелаАнотація:
This thesis presents a novel analytical solution strategy for the zero-inertia (ZI) equations of free surface flow. These equations are utilized herein for routing flood flow in open channels and for simulating excess rainfall runoff on overland planes. The novel solution approach is shown to be both accurate and robust, especially under the complicated and intricate conditions of infiltrating flow on initially dry river beds or soils, e.g., as present in arid and semiarid areas. This is underlain by comparing modeling results of the novel analytical procedure with those of validated numerical solutions. Furthermore, it is shown that the analytical ZI model can deliver a process-oriented portrayal of runoff concentration in the flood-generating parts of the catchment. Subsequently, the novel analytical ZI model is applied for a real-world water management problem in the Sultanate of Oman, Arabian Peninsula. Within an integrated flash flood routing model—which is also presented in this thesis—the novel analytical routing approach helps in accurately matching the dynamics of advancing and infiltrating ephemeral river flow, established as a consequence of release from a groundwater recharge dam. The integrated modeling system houses the aforementioned analytical downstream model and tailor-made, state-of-the-art modeling components to portray the upstream flow processes, dam operation (including evaporation), and spillway release flow. The proposed modeling system can aid in rendering a realistic image of transient transmission losses and dependent flow dynamics. This is of extremely high importance for water resources assessment, as well as for optimizing recharge dam operation strategies in order to maximize downstream transmission losses and, thus, groundwater rechargeDiese Dissertation präsentiert einen neuartigen analytischen Lösungsansatz für das beschleunigungsfreie Wellenmodell (bzw. „Zero-Inertia-Modell“, „ZI-Modell“, oder „diffusives Wellenmodell“). Im Rahmen der Arbeit wird das hergeleitete hydrodynamische Modell sowohl zur Simulation von Freispiegelabflüssen in nichtprismatischen und durchlässigen Gerinnen, als auch für die Beschreibung von auf der Landoberfläche abfließendem Infiltrationsüberschuss eingesetzt. Es wird gezeigt, dass der neuartige analytische Ansatz — im Hinblick auf Massenerhaltung und die exakte Abbildung der Abflussdynamik — akkurate Ergebnisse liefert und gleichzeitig unter komplexen und verwickelten Prozessbedingungen anwendbar ist. So belegt eine vergleichende Analyse mit validierten numerischen Lösungsansätzen die Robustheit des analytischen ZI-Modells. Insbesondere die im Sinne der numerischen Mathematik stabile und genaue Modellierung der gekoppelten Abfluss- und Infiltrationsvorgänge in anfänglich trockenen Gerinnen ist dabei ein Novum. Weiterhin wird die Eignung und Anwendbarkeit des neuartigen Modellansatzes zur Beschreibung der Abflusskonzentrationsprozesse gezeigt. Der neuartige Lösungsansatz wird im Folgenden für ein reales Wassermanagementproblem im Sultanat Oman, Arabische Halbinsel eingesetzt. Als Bestandteil eines integrierten Modellsystems, welches ebenfalls im Rahmen der Dissertation vorgestellt wird, dient das analytische ZI-Modell zur Simulation von infiltrierendem Wadiabfluss, welcher unterstrom von Grundwasseranreicherungsdämmen starke Verluste von Masse und Impuls erfährt. Zusammen mit maßgeschneiderten und dem Stand der Technik entsprechenden Komponenten für die Betriebssimulation des Anreicherungsdammes (inklusive Verdunstung von der freien Seefläche) sowie für die Abbildung der oberstromigen hydrodynamischen Prozesse (ebenfalls inklusive Infiltration) wird der neuartige analytische Ansatz in einem Modellsystem zusammengefasst. Das Modellsystem ist in der Lage ein realistisches Bild der raumzeitlichen Dynamik des Abflusses sowie der Grundwasserneubildung aus infiltrierendem Wadiabfluss zu liefern. Damit stellt das Modellsystem ein wertvolles Werkzeug sowohl zur Wasserdargebotsermittlung, als auch für die Optimierung des Betriebes von Grundwasseranreicherungsdämmen dar
15
Philip, Croné. "Thermo-Elasto-Hydrodynamic lubrication modeling of Tilting Pad Journal Bearings." Licentiate thesis, Luleå tekniska universitet, Maskinelement, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-71105.
Повний текст джерелаАнотація:
The journal bearing is a critical machine element typically used to support rotating motion in high speed machinery. Through the generation of a hydrodynamic pressure in its thin lubricant film,which is usually in the order of 10-100μmthick depending on the diameter of the journal itself, the bearing is able to withstand large loads, both statically and dynamically, while having a very low rate of wear. It is of course essential that these components provide for a safe operation with as little wear and frictional losses as possible and it is therefore of great interest to develop simulation models of constantly increasing accuracy. Typical relevant quantities when designing a bearing are the load carrying capacity, metal/oil temperature, minimum film thickness, stiffness, damping and power loss. Classical lubrication theory builds upon the Navier-Stokes equations which, with the thin film approximation, can be reduced to a single equation which governs the hydrodynamic pressure build up in the lubricant. Since the problem now has been reduced to solving a single non linear partial differential equation in 2 dimensions, a significant advantage in terms of simulation time compared to the full set of Navier-Stokes equations can be enjoyed with an, in most cases, insignificant error of approximation. However, with time, as the need for bearings capable of operating at higher loads,speeds and with new designs involving more complex geometries, such as, for example, textured surfaces, the applicability of classic thin film theory should not be taken for granted, especially not when there is an increasing amount of turbulence involved. The purpose of the work contained in this thesis is to develop and asses the performance of a state of the art 3D TEHD model using the commercial finite element multi physics software COMSOL Multiphysics. Of special interest is the assessment of the Menter Shear Stress Transport (SST) turbulence model, which is a widely used, standard, 2-equation RANS eddy viscosity model, in predicting characteristic values for a bearing operating in the transition range between laminar and turbulent flow. A comparative study is carried out where the present model is benchmarked against experimental data on a large 4 pad tilting pad journal bearing. The present model is also compared to one of the classic models based on thin film theory. The present model is also used to study the influence of the geometry that constitutes the leading edge groove in a tilting pad journal bearing on the turbulence levels. Finally the possibility of using a shear thinning lubricant for reducing the bearing power loss is investigated. The calculations were all performed using the resources of the super computer cluster at HPC2N at Ume ̊a University. The results clearly show the inadequacy of the SST turbulence model when performing calculations on a bearing operating in the transition range between laminar and turbulent flow. Moreover, the model predicts slightly higher average values of turbulence in a leading edge grooved bearing compared to a conventional one, yet a higher maximum value in the latter.
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Smith, Arlynn W. "Light confinement and hydrodynamic modeling of semiconductor structures by volumetric methods." Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/13407.
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Geiger, Sam R. (Sam Rayburn) 1971. "Hydrodynamic modeling of towed buoyant submarine antenna's [sic] in multidirectional seas." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/29045.
Повний текст джерелаАнотація:
Thesis (S.M.)--Joint Program in Oceanographic Engineering (Massachusetts Institute of Technology, Dept. of Ocean Engineering, and the and Woods Hole Oceanographic Institution), 2000.Includes bibliographical references (p. 100-101).
A finite difference computer model is developed to simulate the exposure statistics of a radio frequency buoyant antenna as it is towed in a three-dimensional random seaway. The model allows the user to prescribe antenna properties (length, diameter, density, etc.), sea conditions (significant wave height, development of sea), tow angle, and tow speed. The model then simulates the antenna-sea interaction for the desired duration to collect statistics relating to antenna performance. The model provides design engineers with a tool to predict antenna performance trends, and to conduct design tradeoff studies. The floating antenna envisioned is for use by a submarine operating at modest speed and depth.
by Sam R. Geiger.
S.M.
18
Mirfenderesgi, Golnazalsadat. "Development of a Novel Hydrodynamic Approach for Modeling Whole-plant Transpiration." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1502375927541919.
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Hammond, Andrew Jesse. "Hydrodynamic and Water Quality Simulation of Fecal Coliforms in the Lower Appomattox River, Virginia." Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/10126.
Повний текст джерелаАнотація:
The Virginia Department of Environmental Quality (VADEQ) under the direction of the United States Environmental Protection Agency (USEPA) has listed the lower Appomattox River as impaired because it violates current water quality standards for fecal coliforms. To advance the analytical process by which various scenarios for improving water quality within the estuary are examined, an array of computer-based hydrodynamic and water quality models were investigated. The Dynamic Estuary Model (DYNHYD5), developed by USEPA, was used to simulate hydrodynamics within the lower Appomattox River. The Water Quality Analysis Simulation Program (WASP6.1), also developed by USEPA, was employed to perform water quality simulations of fecal coliforms. Also, a detailed literature review examined DYNHYD5 and WASP6.1 model theory, computer-based model solution techniques, and background hydrodynamic theory.
DYNHYD5 sensitivity analysis showed that the model was most responsive to tidal heights (seaward boundary conditions) both upstream and downstream within the model network. Specific model parameters were varied during calibration until modeled water surface elevations converged on observed water surface elevations. A goodness-of-fit value of 0.749 was determined with linear regression analysis for model calibration. DYNHYD5 input parameter validation was performed with additional observations and a goodness-of-fit value of 0.829 was calculated.
Through sensitivity analysis, WASP6.1 proved to be most responsive to coliform loading rates in the downstream direction and boundary concentrations in the upstream direction. With these results, WASP6.1 input parameters were calibrated against observed fecal coliform concentrations. A goodness-of-fit value of 0.573 was determined with linear regression analysis for model calibration. WASP6.1 input parameter validation was performed with additional observations and a goodness-of-fit value of 0.0002 was calculated.
Model results suggest that hydrodynamic model calibration and validation can be improved with additional tidal height observations at the downstream seaward boundary. Similarly, water quality model calibration and validation can possibly be improved with the aid of detailed, time-variable coliform concentrations at the downstream seaward boundary. Therefore, it is recommended that a water quality sampling station and tidal stage recorder be installed at the confluence of the Appomattox and James Rivers to provide for further testing of estuary hydrodynamic and water quality models.Master of Science
20
Khanal, Anish. "Two Dimensional Hydrodynamic Numerical Simulation of Flow Around Chevrons." OpenSIUC, 2012. https://opensiuc.lib.siu.edu/theses/799.
Повний текст джерелаАнотація:
A chevron is a U-shaped rock structure constructed for improving navigation conditions by diverting majority of flow towards main channel. The objective of this study is to improve understanding of how chevrons affect channel flow. For this study, a two-dimensional numerical hydrodynamic model of a two-km-long reach of the Mississippi River was developed; three chevrons have been constructed in the modeled reach. The model was calibrated by adjusting Manning's n to match predicted and observed water surface elevations (WSELs). The model was validated using measured WSEL and velocity data from two events: a low-flow discharge (4,500 m3/s) and high-flow discharge (14,000 m3/s). At reach scale the model performed well in predicting WSELs. Average difference between model prediction and observed WSEL was 0.23 m in low-flow condition and 0.05 in high flow condition. Root mean square of errors (RMSEs) and mean absolute errors (MAEs) were used to measure the degree of agreement between predicted and measured velocities. At the reach scale there was reasonable agreement between predicted and observed velocities (RMSE = 0.416 m/s and 0.425 m/s, respectively, for low-flow and high-flow conditions). Local differences between predicted and observed velocities were up to 1.5 m/s; this is attributed to uncertainties in the velocity measurements. The model's sensitivity of to changes in Manning's n, eddy viscosity and bathymetry were also analyzed. The sensitivity analysis showed that there are specific areas (e.g., near the banks of the river) which are sensitive to changes in Manning's n. This indicates that spatial distribution of Manning's n is required to increase the accuracy in the model's predictions of velocity. Model was found to be stable in a specific range of eddy viscosity values. Eddy viscosity had little effect on velocity predictions but was important for model stability (i.e., the model was stable only for a range of eddy viscosity values). Reach scale changes in bathymetry had minor impacts on RMSE and MAE. However, local changes in channel bathymetry resulted in differences in velocity predictions as much as ±0.4 m/s.
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Winter, Henry deGraffenried III. "Combining hydrodynamic modeling with nonthermal test particle tracking to improve flare simulations." Thesis, Montana State University, 2009. http://etd.lib.montana.edu/etd/2009/winter/WinterH0509.pdf.
Повний текст джерелаАнотація:
Solar flares remain a subject of intense study in the solar physics community. These huge releases of energy on the Sun have direct consequences for humans on Earth and in space. The processes that impart tremendous amounts of energy are not well understood. In order to test theoretical models of flare formation and evolution, state of the art, numerical codes must be created that can accurately simulate the wide range of electromagnetic radiation emitted by flares. A direct comparison of simulated radiation to increasingly detailed observations will allow scientists to test the validity of theoretical models. To accomplish this task, numerical codes were developed that can simulate both the thermal and nonthermal components of a flaring plasma, their interactions, and their emissions. The HYLOOP code combines a hydrodynamic equation solver with a nonthermal particle tracking code in order to simulate the thermal and nonthermal aspects of a flare. A solar flare was simulated using this new code with a static atmosphere and with a dynamic atmosphere, to illustrate the importance of considering hydrodynamic effects on nonthermal beam evolution. The importance of density gradients in the evolution of nonthermal electron beams was investigated by studying their effects in isolation. The importance of the initial pitch-angle cosine distribution to flare dynamics was investigated. Emission in XRT filters were calculated and analyzed to see if there were soft X-ray signatures that could give clues to the nonthermal particle distributions. Finally the HXR source motions that appeared in the simulations were compared to real observations of this phenomena.
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Geisbert, Jesse Stuart. "Hydrodynamic Modeling for Autonomous Underwater Vehicles Using Computational and Semi-Empirical Methods." Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/33195.
Повний текст джерелаАнотація:
Buoyancy driven underwater gliders, which locomote by modulating their buoyancy and their attitude with moving mass actuators and inflatable bladders, are proving their worth as efficient long-distance, long-duration ocean sampling platforms. Gliders have the capability to travel thousands of kilometers without a need to stop or recharge. There is a need for the development of methods for hydrodynamic modeling. This thesis aims to determine the hydrodynamic parameters for the governing equations of motion for three autonomous underwater vehicles. This approach is two fold, using data obtained from computational flight tests and using a semi-empirical approach. The three vehicles which this thesis focuses on are two gliders (Slocum and XRay/Liberdade), and a third vehicle, the Virginia Tech Miniature autonomous underwater vehicle.Master of Science
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Su, Yuming. "Storm Water Runoff First Flush Modeling and Treatment with a Hydrodynamic Device." Ohio University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1170334793.
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Chilmakui, Chandra Sekhar. "Sediment Transport and Pathogen Indicator Modeling in Lake Pontchartrain." ScholarWorks@UNO, 2006. http://scholarworks.uno.edu/td/326.
Повний текст джерелаАнотація:
A nested three dimensional numerical modeling application was developed to determine the fate of pathogen indicators in Lake Pontchartrain discharged from its tributaries. To accomplish this, Estuarine, coastal and ocean model with sediment (ECOMSED) was implemented to simulate various processes that would determine the fate and transport of fecal coliform bacteria in the lake. The processes included hydrodynamics, waves, sediment transport, and the decay and transport of the fecal coliforms. Wind and tidal effects were accounted along with the freshwater inflows. All the components of the modeling application were calibrated and validated using measured data sets. Field measurements of the conventional water quality parameters and fecal coliform levels were used to calibrate and validate the pathogen indicator transport. The decay of the fecal coliforms was based on the literature and laboratory tests. The sediment transport module was calibrated based on the satellite reflectance data in the lake. The north shore near-field model indicated that the fecal coliform plume can be highly dynamic and sporadic depending on the wind and tide conditions. It also showed that the period of impact due to a storm event on the fecal coliform levels in the lake can be anywhere from 1.5 days for a typical summer event to 4 days for an extreme winter event. The model studies showed that the zone of impact of the stormwater from the river was limited to a few hundred meters from the river mouth. Finally, the modeling framework developed for the north shore was successfully applied to the south shore of Lake Pontchartrain to simulate fate and transport of fecal coliforms discharged through the urban stormwater outfalls.
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Almazán, Torres Lídia [Verfasser], Thorsten [Gutachter] Pöschel, and Clara [Gutachter] Salueña. "Hydrodynamic Modeling of Granular Materials / Lídia Almazán Torres ; Gutachter: Thorsten Pöschel, Clara Salueña." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2017. http://d-nb.info/1131876512/34.
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Munoz, Diego Jose. "Modeling and Simulation of Circumstellar Disks with the Next Generation of Hydrodynamic Solvers." Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:11151.
Повний текст джерелаАнотація:
This thesis is a computational study of circumstellar gas disks, with a special focus on modeling techniques and on numerical methods not only as scientific tools but also as a target of study. In particular, in-depth discussions are included on the main numerical strategy used, namely the moving-mesh method for astrophysical hydrodynamics. In this work, the moving-mesh approach is used to simulate circumstellar disks for the first time.Astronomy
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Pavlyukova, Tatiana. "A 3-D Hydrodynamic Modeling at Head of Passes of the Mississippi River." ScholarWorks@UNO, 2014. http://scholarworks.uno.edu/td/1827.
Повний текст джерелаАнотація:
A 3-D numerical model of the Head of Passes and Bird’s Foot Delta of the Mississippi River- was developed. The model was based on Delft3D and simulates the hydrodynamics and salinity transport for Head of Passes area from RM 6.5 to Gulf of Mexico. The model was calibrated, validated, and used to predict the response of the river to certain stimuli, such as - channel closures, channel modifications and diversions. The model includes West Bay, Southwest Pass, South Pass, Pass-A-Loutre and Main Pass. Three basic cases were developed: existing conditions, closure of Southwest Pass with a levee of 1.5m with dredging of Pass-A-Loutre to 13.7 meter depth, and closure of Southwest Pass and South Pass with dredging of Pass-A-Loutre to 13.7 meter (45 ft) depth. Salinity has been added to the model. It has been proved that salinity intrusion has a significant impact on the model instantaneous discharge. For all passes except Southwest Pass instantaneous discharge decreases almost in half. Closure of Southwest Pass and dredging of Pass-A-Loutre leads to changes in flow speed and distribution. As a result Pass-A-Loutre becomes a main River channel.
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Bassler, Christopher Colby. "Analysis and Modeling of Hydrodynamic Components for Ship Roll Motion in Heavy Weather." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/23258.
Повний текст джерелаАнотація:
Ship roll motion has been the subject of many studies, because of the complexities associated with this mode of ship motion, and its impact on operability, safety, and survivability. Estimation and prediction of the energy transfer and dissipation of the hydrodynamic components, added inertia and damping, is essential to accurately describe the roll motions of a ship. This is especially true for ship operations in moderate to extreme sea conditions. In these conditions, a complex process of energy transfer occurs, which alters the physical behavior of the hydrodynamic components, and ultimately affects the amplitude of ship roll motion. Bilge keels have been used on ships for nearly two centuries, to increase damping and reduce the severity of roll motions experienced by a ship in waves. Because ship motions are more severe in extreme sea conditions, large roll angles may occur. With the possibility of crew injury, cargo damage, or even capsize, it is important to understand the behavior of the roll added inertia and damping for these conditions. Dead ship conditions, where ships may experience excitation from beam, or near beam, seas present a worst case scenario in heavy weather. The behavior of a ship in this condition should be considered in both the design and assessment of seakeeping performance.
In this study, hydrodynamic component models of roll added inertia and roll damping were examined and assessed to be unsuitable for accurate prediction of ship motions in heavy weather. A series of model experiments and numerical studies were carried out and analyzed to provide improved understanding of the essential physical phenomena which affect the hydrodynamic components and occur during large amplitude roll motion. These observations served to confirm the hypothesis that the existing models for roll added inertia and damping in large amplitude motions are not sufficient. The change in added inertia and damping behavior for large roll motion is largely due to the effects of hull form geometry, including the bilge keels and topside geometry, and their interactions with the free surface. Therefore, the changes in added inertia and damping must be considered in models to describe and predict roll motions in severe wave environments.
Based on the observations and analysis from both experimental and numerical methods, several time-domain model formulations were proposed and examined to model hydrodynamic components of large amplitude roll motions. These time-domain formulations included an analytical model with memory effects, a piecewise formulation, and several possibilities for a bilge keel force model. Although a piecewise model for roll damping was proposed, which can improve the applicability of traditional formulations for roll damping to heavy weather conditions, a further attempt was undertaken to develop a more detailed model specifically for the bilge keel force. This model was based on the consideration of large amplitude effects on the hydrodynamic components of the bilge keel force. Both the piecewise and bilge keel force models have the possibility to enable improved accuracy of potential flow-based numerical prediction of ship roll motion in heavy weather. However, additional development remains to address issues for further practical implementation.
Ph. D.
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Baird, Eric S. "Hydrodynamic and thermal modeling of two-dimensional microdroplet arrays for digitized heat transfer." Connect to online resource, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3315772.
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Van, Glubt Sarah. "Hydrodynamic and Water Quality Modeling of the Chehalis River Using CE-QUAL-W2." PDXScholar, 2017. https://pdxscholar.library.pdx.edu/open_access_etds/3486.
Повний текст джерелаАнотація:
The Chehalis River Basin is located in the southwest region of Washington State, originating in the Olympic Mountains and flowing to Grays Harbor and the Pacific Ocean. The Chehalis River is over 125 miles, exists within five counties, and flows through agricultural, residential, industrial, and forest land areas. Four major rivers discharge to the Chehalis River, as well as many smaller creeks, five wastewater treatment plants, and groundwater flows.
Flooding is a major problem in the relatively flat areas surrounding the cities of Chehalis and Centralia, with severe consequences for property, safety and transportation. As a result, construction of a flood-control dam in the upper basin has been proposed. One major concern of constructing a dam is the potentially severe impacts to fish health and habitat. The Chehalis River has routinely violated water quality standards for primarily temperature and dissolved oxygen, and has had multiple water quality and Total Maximum Daily Load studies beginning in 1990.
CE-QUAL-W2, a two-dimensional (longitudinal and vertical) hydrodynamic and water quality model, was used to simulate the Chehalis River, including free flowing river stretches and stratified (in summer) lake-like stretches. The goals of this research were to assess the flood retention structure's impacts to water quality, as well as river responses to potential climate change scenarios.
In order to use the model to achieve these goals, calibration to field data for flow, temperature, and water quality constituents was performed. This involved developing meteorological data, riparian shading data, and flow, temperature, water quality records for all tributaries during the calibration period of January 1, 2013 to December 31, 2014. System cross-sectional geometry data were also required for the model grid. Because of the short travel time in the river, the model was sensitive to boundary condition data, wind speed, bathymetry, nutrient kinetics, and algae, epiphyton, and zooplankton kinetics.
Future conditions showed predictions of warmer water temperatures and slight changes to water quality conditions on the river. As fish in the area prefer cooler water temperatures, this could pose a threat to fish health and habitat. Flood retention structures also showed impacts to river temperature and water quality. Structures with the purpose of flood retention only (only operating during times of flooding) gave model predictions for daily maximum temperature higher than structures that employed flood retention and flow augmentation (operating during all times of the year). This suggested the management of flow passage or retention by the dam is important for water quality on the river.
As this research continues improvements will be made, particularly to temperature and water quality constituents. Additional data for the system would be beneficial to this process. Model predictions of temperature were sensitive to meteorological data, including cloud cover, which were largely estimated based on solar radiation. Additional meteorological data throughout the basin would be useful to temperature results. Temperature results were also sensitive to the model bathymetry, and additional investigations into segments widths and water depths may improve temperature predictions.
Water quality constituent data were largely lacking for the system. Many estimation techniques and approximations were used for input water quality constituents for the model upstream boundary and tributaries when little or no data were available, introducing uncertainty to the model. It was not possible to calibrate pH to field data because alkalinity data were essentially unavailable. However, other constituents had good agreement between model predictions and field data, including dissolved oxygen, nitrates, total phosphorus, and total suspended solids.
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Bongo, Njeng Alex Stéphane. "Experimental study and modeling of hydrodynamic and heating characteristics of flighted rotary kilns." Thesis, Ecole nationale des Mines d'Albi-Carmaux, 2015. http://www.theses.fr/2015EMAC0009/document.
Повний текст джерелаАнотація:
Ce travail porte sur l'étude de fours tournants équipés de releveurs. Ce sont des contacteurs gaz/solide largement répandus dans de nombreux secteurs industriels mettant en oeuvre des solides divisés. Cependant en raison d'une faible connaissance du fonctionnement de ces équipements notamment en matière d'écoulement ou de transfert thermique, leur utilisation repose encore beaucoup sur le savoir faire des opérateurs acquis avec le temps. Ainsi ce travail vise à fournir aux ingénieurs des outils de connaissance et d'extrapolation pour les accompagner dans les phases de dimensionnement, mais aussi d'optimisation de procédés existants, en particulier pour des fours tournants en chauffage indirect et équipés de releveurs. La première partie de cette étude porte sur l'influence des conditions opératoires sur l'hydrodynamique des solides divisés de forme et taille différentes. Pour ce faire, des procédures expérimentales pour la mesure de distribution des temps de séjours des particules solides ont été mises en oeuvres. Deux pilotes de four tournant ont été utilisés. Ces derniers ont un ratio longueur sur diamètre équivalent mais un ratio de taille de 2. L'hydrodynamique des fours a été caractérisée quantitativement à partir des résultats expérimentaux en terme de temps de séjour des solides, taux de remplissage du four ainsi que de la dispersion axiale des particules. Ces derniers ont été modélisés par analyse dimensionnelle dans un souci de généralité en prenant en compte la présence d'éléments internes (releveurs, grille) ou diaphragmes en sortie, mais aussi des paramètres opératoires tels que la vitesse de rotation du tube, son inclinaison ou le débit des particules solides. La seconde partie de cette étude s'intéresse aux processus de transfert thermique dans les fours tournants en chauffage indirect et équipés de releveurs. Cette étude repose sur la mesure des profils de température à la paroi, dans la phase gazeuse et le lit de particules solides. L'analyse de ces profils de température se focalise sur la détermination des coefficients de transfert de chaleur entre la paroi et le lit de solides d'une part, et entre la paroi et le gaz d'autre part. Une méthode d'analyse globale de système mince et un bilan global intégrant la puissance fournie pour la chauffe sont utilisés pour la détermination de ces coefficients de transfert. Les résultats obtenus permettent d'une part de mettre en évidence l'effet des releveurs ainsi que l'influence des paramètres opératoires sur ces coefficients de transfert de chaleur et d'autre part d'établir par analyse dimensionnelle des modèles pour ces derniers. Enfin, ce travail se termine par la mise en place d'un modèle dynamique simplifié de four tournant en chauffage indirect permettant la détermination des profils de température le long du four et pouvant être facilement adapté à divers procédésThe present work addresses a fundamental study on flighted rotary kilns. They are gas-solid reactors, used in a variety of industries to process heterogeneous media. However, operating these kilns mainly relies on the know-how of operators due to insufficient fundamental understanding. The aim of this work is to provide engineers with relevant tools and models to assist in the design stage and the performance improvement of existing operating process units, in particular indirectly heated rotary kilns, inclined and equipped with lifters. In the first part, we studied the effects of operating parameters on the flow of materials of differing properties and shape. For this purpose, residence time distribution measurements were performed through experimental stimulus response tests. Two pilot-scale rotary kilns with similar length-to-diameter ratios, but a dimension ratio of about two were used in this study. We focused on the effects of lifter shape and configurations. The effects of the rotational speed, the kiln slope, the mass flow rate and the exit dam height were also analyzed. The flow of solids was quantitatively characterized primarily by the experimental mean residence time, hold-up, and axial dispersion coefficient. Using a dimensional analysis, models were established to predict the mean residence time, the filling degree and the axial dispersion coefficient, providing basic information on the kiln design, solid particle properties and operating conditions. In the second part, we studied the heat transfer mechanisms occurring in the flighted rotary kiln by measuring temperature profiles at the wall, the freeboard gas and the bulk of solids. Analysis of the temperature profiles focused on two main issues: assessment of the heat transfer coefficient between wall and gas, and assessment of the heat transfer coefficient between wall and solid particles. The lumped system analysis and a heat balance using the power supplied for the heating were applied to determine the experimental heat transfer coefficients. The effects of operating conditions and lifting flights were analyzed. Both heat transfer coefficients were then correlated through dimensional considerations. Lastly a global dynamic model mainly based on the models developed in this study can be used to determine wall, gas and bulk solids axial temperature profiles in an indirectly heated flighted rotary kiln. This global model needs to be completed with specific models related to a reaction so as to be used as a framework for the simulation of specific industrial rotary kilns
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Nelson, Timothy L. "Hydrodynamic Controls on the Morphodynamic Evolution of Subaqueous Landforms." ScholarWorks@UNO, 2017. https://scholarworks.uno.edu/td/2425.
Повний текст джерелаАнотація:
The southern Chandeleur Islands are an ideal setting to study shoal evolution given their history of submergence and re-emergence. Here, numerical models shed light on the attendant processes contributing to shoal recovery/reemergence following a destructive storm event. Simulations of a synthetic winter storm along a cross-shore profile using Xbeach shows that convergence of wave-induced sediment transport associated with repeated passage of cold-fronts initiates aggradation, but does not lead to reemergence. A Delft3d model of the entire island chain shows that as these landforms aggrade alongshore processes driven by incident wave refraction on the shoal platform, backbarrier circulation and resulting transport become increasingly important for continued aggradation and eventual emergence. Aggradation magnitudes are a function of depth ranging from 2 – 10 mm per event (onset to recovery to near mean sea level). In the absence of big storms, this modest aggradation can be more than one meter in a few years.
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Al-Faesly, Taofiq Qassim. "Extreme Hydrodynamic Loading on Near-Shore Structures." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34179.
Повний текст джерелаАнотація:
The main objective of this study was to investigate and quantify the impact of extreme hydrodynamic forces, similar to those generated by tsunami-induced inundation, on structural elements. As part of a comprehensive experimental program and analytical study, pressures, base shear forces, and base overturning moments generated by hydraulic bores on structural models of various shapes were studied. In addition, the impact force induced by waterborne wooden debris of different shapes and masses on the structural models was also investigated. Two structural models, one with circular and the other with square cross-section, were installed individually downstream of a dam-break wave in a high-discharge flume. Three impounding water heights (550, 850 and 1150 mm) were used to produce dam-break waves, which have been shown to be analogous to tsunami-induced coastal inundation in the form of highly turbulent hydraulic bores. Time-history responses of the structural models were recorded, including: pressures, base shear forces, base overturning moments, lateral displacements, and accelerations. In addition, the flow depth-time histories were recorded at various locations along the length of the flume. Regular and high-speed video cameras were used to monitor the bore-structure interaction. The effect of initial flume bed condition (“wet” or “dry” bed) on the forces and pressures exerted on the structural models were also investigated. Moreover, the vertical distribution of pressure around the models was captured. Simple low-height walls with various geometries were installed upstream from the structural models to investigate their efficiency as tsunami mitigation measures. The experimentally recorded data were compared with those estimated from currently available formulations.
The results and analysis of the simulated tsunami-induced bore presented in this study will be of significant use to better estimate forces exerted on structures by tsunami-induced turbulent bores. It is expected that this work will contribute to the new ASCE7 Chapter 6 - Tsunami Loads and Effects in which two of this author’s academic supervisors, Drs. Ioan Nistor and Dan Palermo, are members.
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Pawar, Suraj Arun. "Hydrodynamic Design of Highly Loaded Torque-neutral Ducted Propulsor for Autonomous Underwater Vehicles." Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/86888.
Повний текст джерелаАнотація:
The design method for marine propulsor (propeller/stator) is presented for an autonomous underwater vehicle (AUV) that operates at a very high loading condition. The design method is applied to Virginia Tech Dragon AUV. It is based on the parametric geometry definition for the propulsor, use of high-fidelity CFD RANSE solver with the transition model, construction of the surrogate model, and multi-objective genetic optimization algorithm. The CFD model is validated using the paint pattern visualization on the surface of the propeller for an open propeller at model scale. The CFD model is then applied to study hydrodynamics of ducted propellers such as forces and moments, tip leakage vortex, leading-edge flow separation, and counter-rotating vortices formed at the duct trailing edge. The effect of variation of thickness for stator blades and different approaches for modeling the postswirl stator is presented. The field trials for Dragon AUV shows that there is a good correlation between expected and achieved design speed under tow condition with the designed base propulsor. The marine propulsor design is further improved with an objective to maximize the propulsive efficiency and minimize the rolling of AUV. The stator is found to eliminate the swirl component of velocity present in the wake of the propeller to the maximum extent. The propulsor designed using this method (surrogate-based optimization) is demonstrated to have an improved torque balance characteristic with a slight improvement in efficiency than the base propulsor design.Master of Science
The propulsion system is the critical design element for an AUV, especially if it is towing a large payload. The propulsor for towing AUVs has to provide a very large thrust and hence the propulsor is highly loaded. The propeller has to rotate at very high speed to produce the required thrust and is likely to cavitate at this high speed. Also at this high loading condition, the maximum ideal efficiency of the propulsor is very less. Another challenge is the induced torque from the propeller on AUV that can cause the rolling of an AUV which is undesirable. This problem can be addressed by installing the stator behind the propeller that will produce torque in the opposite direction of the propeller torque. In this work, we present a design methodology for marine propulsor (propeller/stator) that can be used in AUV towing a large payload. The propulsor designed using this method has improved torque characteristics and has the efficiency close to 80 % of the ideal efficiency of ducted propeller at that loading condition.
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Nouyrigat, Nicolas. "Hydrodynamic modeling of poly-solid reactive circulating fluidized beds : Application to Chemical Looping Combustion." Phd thesis, Toulouse, INPT, 2012. http://oatao.univ-toulouse.fr/9189/1/nouyrigat.pdf.
Повний текст джерелаАнотація:
This work deals with the development, validation and application of a model of Chemical Looping Combustion (CLC) in a circulating fluidized bed system. Chapter 1 is an introduction on Chemical Looping Combustion. It rst presents the most important utilizations of coal in the energy industry. Then, it shows that because of the CO2 capture policy, new technologies have been developed in the frame of post-combustion, pre-combustion and oxy-combustion. Then, the Chemical Looping Combustion technology is presented. It introduces multiple challenges: the choice of the Metal Oxide or the denition of the operating point for the fuel reactor. Finally, it shows that there are two specicities for CFD modeling: the influence of the collisions between particles of different species and the local production of gas in the reactor due to the gasication of coal particles. Chapter 2 outlines the CFD modeling approach: the Eulerian-Eulerian approach extended to flows involving different types of particles and coupled with the chemical reactions. Chapter 3 consists in the validation of the CFD model on mono-solid (monodisperse and poly-disperse) and poly-solid flows with the experimental results coming from an ALSTOM pilot plant based at the Universite Tchnologique de Compiegne (France). The relevance of modeling the polydispersity of a solid phase is shown and the influence of small particles in a CFB of large particles is characterized. This chapter shows that the pilot plant hydrodynamics can be predicted by an Eulerian-Eulerian approach. Chapter 4 consists in the validation of the CFD model on an extreme bi-solid CFB of particles of same density but whith a large particle diameter ratio. Moreover, the terminal settling velocity of the largest particles are twice bigger than the fluidization velocity: the hydrodynamics of the large particles are given by the hydrodynamics of the smallest. An experiment performed by Fabre (1995) showed that large particles can circulate through the bed in those operating conditions. Our simulations predicted a circulation of large particles, but underestimated it. It is shown that it can be due to mesh size eect. Finally, a simulation in a periodic box of this case was dened and allowed us to show the major influence of collisions between species. Chapter 5 presents the simulation of a hot reactive CLC pilot plant under construction in Darmstadt (Germany). The simulations account for the chemical reactions and describe its eect on the hydrodynamics. Different geometries and operating conditions are tested.
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El-Solh, Safinaz. "SPH Modeling of Solitary Waves and Resulting Hydrodynamic Forces on Vertical and Sloping Walls." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/23778.
Повний текст джерелаАнотація:
Currently, the accurate prediction of the impact of an extreme wave on infrastructure located near shore is difficult to assess. There is a lack of established methods to accurately quantify these impacts. Extreme waves, such as tsunamis generate, through breaking, extremely powerful hydraulic bores that impact and significantly damage coastal structures and buildings located close to the shoreline. The damage induced by such hydraulic bores is often due to structural failure. Examples of devastating coastal disasters are the 2004 Indian Ocean Tsunami, 2005 Hurricane Katrina and most recently, the 2011 Tohoku Japan Tsunami. As a result, more advanced research is needed to estimate the magnitude of forces exerted on structures by such bores.
This research presents results of a numerical model based on the Smoothed Particle Hydrodynamics (SPH) method which is used to simulate the impact of extreme hydrodynamic forces on shore protection walls. Typically, fluids are modeled numerically based on a Lagrangian approach, an Eulerian approach or a combination of the two. Many of the common problems that arise from using more traditional techniques can be avoided through the use of SPH-based models. Such challenges include the model computational efficiency in terms of complexity of implementation. The SPH method allows water particles to be individually modeled, each with their own characteristics, which then accurately depicts the behavior and properties of the flow field. An open source code, known as SPHysics, was used to run the simulations presented in this thesis. Several cases analysed consist of hydraulic bores impacting a flat vertical wall as well as a sloping seawall. The analysis includes comparisons of the numerical results with published experimental data. The model is shown to accurately reproduce the formation of solitary waves as well as their propagation and breaking. The impacting bore profiles as well as the resulting pressures are also efficiently simulated using the model.
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Teran, Gonzalez Grecia A. "3-D Hydrodynamic and Non-Cohesive Sediment Transport Modeling in the Lower Mississippi River." ScholarWorks@UNO, 2014. http://scholarworks.uno.edu/td/1837.
Повний текст джерелаАнотація:
The purpose of this research is to develop a 3-D numerical model on the Lower Mississippi River to simulate hydrodynamics and non-cohesive sediment transport. The study reach extends from Bonnet Carré Spillway (RM 127) to Head of Passes (RM 0). Delft3D with sigma coordinates was selected as the river modeling tool. This model River domain is characterized by a complex distributary system that connects the Mississippi River to the Gulf of Mexico. The boundary conditions were: water levels in the Gulf and Head of Passes; and discharges upstream. For the calibration, there are observed data for both types of boundary conditions. Several periods of high discharge were simulated to compare water level, discharge, velocity profiles and sediment transport with measurements and accomplish calibration and validation of the model. A calibrated 3-D model has been developed with the following %RMSE: 5% for stage; 6% for discharge; and 5% for sand load.
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Bruckner, Robert Jack. "Simulation and Modeling of the Hydrodynamic, Thermal, and Structural Behavior of Foil Thrust Bearings." Case Western Reserve University School of Graduate Studies / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=case1089304186.
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Chang, Jen. "Hydrodynamic modeling and feasibility study of harnessing tidal power at the Bay of Fundy." View ebook online, 2008. http://digitallibrary.usc.edu/assetserver/controller/item/etd-Chang-20080312.pdf.
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O'Neil, Sean. "THREE DIMENSIONAL MOBILE BED DYNAMICS FOR SEDIMENT TRANSPORT MODELING." The Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=osu1032548958.
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Cole, Robert Edward. "Numerical Modeling of Air Cushion Vehicle Flexible Seals." Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/83828.
Повний текст джерелаАнотація:
Air cushion vehicle flexible seals operate in a complex and chaotic environment dominated by fluid-structure interaction. An efficient means to explore interdependencies between various governing parameters that affect performance is through high fidelity numerical simulation. As previous numerical efforts have employed separate iterative partitioned solvers, or have implemented simplified physics, the approaches have been complex, computationally expensive, or of limited utility. This research effort performs numerical simulations to verify and validate the commercial multi-physics tool STAR-CCM+ as a stand-alone partitioned approach for fluid-structure interaction problems with or without a free surface. A dimensional analysis is first conducted to identify potential non-dimensional forms of parameters related to seal resistance. Then, an implicit, Reynolds-averaged Navier-Stokes finite volume fluid solver is coupled to an implicit, nonlinear finite element structural solver to successfully replicate benchmark results for an elastic beam in unsteady laminar flow. To validate the implementation as a seal parameter exploratory tool, a planer bow seal model is developed and results are obtained for various cushion pressures and inflow speeds. Previous numerical and experimental results for deflection and resistance are compared, showing good agreement. An uncertainty analysis for inflow velocity reveals an inversely proportional resistance dependency. Using Abaqus/Explicit, methodologies are also developed for a two-way, loosely coupled explicit approach to large deformation fluid-structure interaction problems, with and without a free surface. Following numerous verification and validation problems, Abaqus is ultimately abandoned due to the inability to converge the fluid pressure field and achieve steady state. This work is a stepping stone for future researchers having interests in ACV seal design and other large deformation, fluid-structure interaction problems. By modeling all necessary physics within a verified and validated stand-alone approach, a designer's ability to comprehensively investigate seal geometries and interactions has never been more promising.Ph. D.
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Mukhtasor. "Hydrodynamic modeling and ecological risk-based design of produced water discharge from an offshore platform." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ62454.pdf.
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St-Germain, Philippe. "Numerical Modeling of Tsunami-induced Hydrodynamic Forces on Free-standing Structures Using the SPH Method." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23527.
Повний текст джерелаАнотація:
Tsunamis are among the most terrifying and complex physical phenomena potentially affecting almost all coastal regions of the Earth. Tsunami waves propagate in the ocean over thousands of kilometres away from their generating source at considerable speeds. Among several other tsunamis that occurred during the past decade, the 2004 Indian Ocean Tsunami and the 2011 Tohoku Tsunami in Japan, considered to be the deadliest and costliest natural disasters in the history of mankind, respectively, have hit wide stretches of densely populated coastal areas. During these major events, severe destruction of inland structures resulted from the action of extreme hydrodynamic forces induced by tsunami flooding. Subsequent field surveys in which researchers from the University of Ottawa participated ultimately revealed that, in contrast to seismic forces, such hydrodynamic forces are not taken into proper consideration when designing buildings for tsunami prone areas. In view of these limitations, a novel interdisciplinary hydraulic-structural engineering research program was initiated at the University of Ottawa, in cooperation with the Canadian Hydraulic Centre of the National Research Council, to help develop guidelines for the sound design of nearshore structures located in such areas.
The present study aims to simulate the physical laboratory experiments performed within the aforementioned research program using a single-phase three-dimensional weakly compressible Smoothed Particle Hydrodynamics (SPH) numerical model. These experiments consist in the violent impact of rapidly advancing tsunami-like hydraulic bores with individual slender structural elements. Such bores are emulated based on the classic dam-break problem. The quantitatively compared measurements include the time-history of the net base horizontal force and of the pressure distribution acting on columns of square and circular cross-sections, as well as flow characteristics such as bore-front velocity and water surface elevation. Good agreement was obtained. Results show that the magnitude and duration of the impulsive force at initial bore impact depend on the degree of entrapped air in the bore-front. The latter was found to increase considerably if the bed of the experimental flume is covered with a thin water layer of even just a few millimetres.
In order to avoid large fluctuations in the pressure field and to obtain accurate simulations of the hydrodynamic forces, a Riemann solver-based formulation of the SPH method is utilized. However, this formulation induces excessive numerical diffusion, as sudden and large water surface deformations, such as splashing at initial bore impact, are less accurately reproduced. To investigate this particular issue, the small-scale physical experiment of Kleefsman et al. (2005) is also considered and modeled.
Lastly, taking full advantage of the validated numerical model to better understand the underlying flow dynamics, the influence of the experimental test geometry and of the bed condition (i.e. dry vs. wet) is investigated. Numerical results show that when a bore propagates over a wet bed, its front is both deeper and steeper and it also has a lower velocity compared to when it propagates over a dry bed. These differences significantly affect the pressure distributions and resulting hydrodynamic forces acting on impacted structures.
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Piché, Steffanie. "Numerical Modeling of Tsunami Bore Attenuation and Extreme Hydrodynamic Impact Forces Using the SPH Method." Thèse, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/30456.
Повний текст джерелаАнотація:
Understanding the impact of coastal forests on the propagation of rapidly advancing onshore tsunami bores is difficult due to complexity of this phenomenon and the large amount of parameters which must be considered. The research presented in the thesis focuses on understanding the protective effect of the coastal forest on the forces generated by the tsunami and its ability to reduce the propagation and velocity of the incoming tsunami bore. Concern for this method of protecting the coast from tsunamis is based on the effectiveness of the forest and its ability to withstand the impact forces caused by both the bore and the debris carried along by it. The devastation caused by the tsunami has been investigated in recent examples such as the 2011 Tohoku Tsunami in Japan and the Indian Ocean Tsunami which occurred in 2004.
This research examines the reduction of the spatial extent of the tsunami bore inundation and runup due to the presence of the coastal forest, and attempts to quantify the impact forces induced by the tsunami bores and debris impact on the structures. This research work was performed using a numerical model based on the Smoothed Particle Hydrodynamics (SPH) method which is a single-phase three-dimensional model. The simulations performed in this study were separated into three sections. The first section focused on the reduction of the extent of the tsunami inundation and the magnitude of the bore velocity by the coastal forest. This section included the analysis of the hydrodynamic forces acting on the individual trees. The second section involved the numerical modeling of some of the physical laboratory experiments performed by researchers at the University of Ottawa, in cooperation with colleagues from the Ocean, Coastal and River Engineering Lab at the National Research Council, Ottawa, in an attempt to validate the movement and impact forces of floating driftwood on a column. The final section modeled the movement and impact of floating debris traveling through a large-scale model of a coastal forest.
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Cedillo, Paula. "Hydrodynamic modeling of the Green Bay of Lake Michigan using the environmental fluid dynamics code." Thesis, The University of Wisconsin - Milwaukee, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=1606696.
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In this project we created a hydrodynamic model of the Lower Green Bay of Lake Michigan in Wisconsin, United States using the Visual Environmental Fluid Dynamics Code (EFDC). The model includes four tributary rivers to Lower Green Bay as well as the open boundary flow conditions at Chambers Island. This case study is used to: 1) compare the results obtained with a previous study of Lower Green Bay to validate the creation of the model 2) examine the hydrodynamics of the bay, and 3) create a framework for future studies at Lower Green Bay. The Geographic Information used to build the Grid was obtained from the NOAA web site. Meteorological and flow information was obtained from the National Weather Service and USGS web sites, respectively. It was necessary to create a new model grid as a platform for future studies of Lower Green Bay, and the Visual EFDC 1.2 code was a useful tool in the development of the grid. However, some limitations in the code made the creation of the grid a challenge. In this project, we summarize the process used to overcome challenges in creating a correct grid, and analyze the hydrodynamic results of the model simulation for the period between June and October 2011. Overall, we conclude that the model reproduces field data reasonably well, and a correct modeling framework for hydrodynamic modeling of Lower Green Bay was created.
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Lakshmikanth, Anand. "Non-Destructive Evaluation and Mathematical Modeling of Beef Loins Subjected to High Hydrodynamic Pressure Treatment." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/28814.
Повний текст джерелаАнотація:
High hydrodynamic pressure (HDP) treatment is a novel non-thermal technology that improves tenderness in foods by subjecting foods to underwater shock waves. In this study non-destructive and destructive testing methods, along with two mathematical models were explored to predict biomechanical behavior of beef loins subjected to HDP-treament.
The first study involved utilizing ultrasound and imaging techniques to predict textural changes in beef loins subjected to HDP-treatment using Warner-Braztler shear force (WBS) scores and texture profile analysis (TPA) features for correlation. Ultrasound velocity correlated very poorly with the WBS scores and TPA features, whereas the imaging features correlated better with higher r-values. The effect of HDP-treatment variables on WBS and TPA features indicated that amount of charge had no significant effects when compared to location of sample and container size during treatment.
Two mathematical models were used to simulate deformational behavior in beef loins. The first study used a rheological based modeling of protein gel as a preliminary study. Results from the first modeling study indicated no viscous interactions in the model and complete deformation failure at pressures exceeding 50 kPa, which was contrary to the real-life process conditions which use pressures in the order of MPa. The second modeling study used a finite element method approach to model elastic behavior. Shock wave was modeled as a non-linear and linear propagating wave. The non-linear model indicated no deformation response, whereas the linear model indicated realistic deformation response assuming transverse isotropy of the model beef loin.
The last study correlated small- and large-strain measurements using stress relaxation and elastic coefficients of the stiffness matrix as small-strain measures and results of the study indicated very high correlation between elastic coefficients c11, c22, and c44 with TPA cohesiveness (r > 0.9), and springiness (r > 0.85). Overall results of this study indicated a need for further research in estimating mechanical properties of beef loins in order to understand the dynamics of HDP-treatment process better.Ph. D.
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Jung, Hahn Chul. "Wetland Hydrodynamics Using Interferometric Synthetic Aperture Radar, Remote Sensing, and Modeling." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1291661296.
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Setegn, Shimelis Gebriye. "Modelling Hydrological and Hydrodynamic Processes in Lake Tana Basin, Ethiopia." Doctoral thesis, KTH, Vattendragsteknik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-12024.
Повний текст джерелаАнотація:
Lake Tana Basin is of significant importance to Ethiopia concerning water resources aspects and the ecological balance of the area. The growing high demands in utilizing the high potentials of water resource of the Lake to its maximal limit, pictures a disturbing future for the Lake. The objective of this study was to assess the influence of topography, soil, land use and climatic varia-bility on the hydrological and hydrodynamic processes of the Lake Tana Basin. The physically based SWAT model was successfully calibrated and validated for flow and sediment yield. Se-quential uncertainty fitting (SUFI-2), parameter solution (ParaSol) and generalized likelihood un-certainty estimation (GLUE) calibration and uncertainty analysis methods were compared and used for the set-up of the SWAT model. There is a good agreement between the measured and simulated flows and sediment yields. SWAT and GIS based decision support system that uses multi-criteria evaluation (MCE) was used to identify the most vulnerable areas to soil erosion in the basin. The results indicated that 12 to 30.5% of the watershed is high erosion potential. Pro-jected changes in precipitation and temperature in the basin for two seasons were analyzed using outputs from fifteen global climate models (GCMs). A historical-modification procedure was used to downscale large scale outputs from GCM models to watershed-scale climate data. The results showed significant changes in streamflow and other hydrological parameters in the period between 2045-2100. SWAT was combined with a three dimensional hydrodynamic model, GEMSS to investigate the flow structure, stratification, the flushing time, lake water balance and finally the Lake‘s water level response to planned water removal. We have found an alarming and dramatic fall of the water levels in Lake Tana as response to the planned water withdrawal. The combination of the two models can be used as a decision support tools to better understand and manage land and water resources in watersheds and waterbodies. The study showed that the Lake Tana Basin may experience a negative change in water balance in the forthcoming decades due to climate change as well as over abstraction of water resources.QC 20100720
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Shao, Zhiyu S. "TWO-DIMENSIONAL HYDRODYNAMIC MODELING OF TWO-PHASE FLOW FOR UNDERSTANDING GEYSER PHENOMENA IN URBAN STORMWATER SYSTEM." UKnowledge, 2013. http://uknowledge.uky.edu/ce_etds/5.
Повний текст джерелаАнотація:
During intense rain events a stormwater system can fill rapidly and undergo a transition from open channel flow to pressurized flow. This transition can create large discrete pockets of trapped air in the system. These pockets are pressurized in the horizontal reaches of the system and then are released through vertical vents. In extreme cases, the transition and release of air pockets can create a geyser feature.
The current models are inadequate for simulating mixed flows with complicated air-water interactions, such as geysers. Additionally, the simulation of air escaping in the vertical dropshaft is greatly simplified, or completely ignored, in the existing models.
In this work a two-phase numerical model solving the Navier-Stokes equations is developed to investigate the key factors that form geysers. A projection method is used to solve the Navier-Stokes Equation. An advanced two-phase flow model, Volume of Fluid (VOF), is implemented in the Navier-Stokes solver to capture and advance the interface.
This model has been validated with standard two-phase flow test problems that involve significant interface topology changes, air entrainment and violent free surface motion. The results demonstrate the capability of handling complicated two-phase interactions. The numerical results are compared with experimental data and theoretical solutions. The comparisons consistently show satisfactory performance of the model.
The model is applied to a real stormwater system and accurately simulates the pressurization process in a horizontal channel. The two-phase model is applied to simulate air pockets rising and release motion in a vertical riser. The numerical model demonstrates the dominant factors that contribute to geyser formation, including air pocket size, pressurization of main pipe and surcharged state in the vertical riser. It captures the key dynamics of two-phase flow in the vertical riser, consistent with experimental results, suggesting that the code has an excellent potential of extending its use to practical applications.
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Xiao, Feng, and 萧峰. "Hydrodynamic property and breakage behavior of particle aggregates in water: theoretical modeling, CFD simulationand PIV investigation." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B4284146X.
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