Estudos sobre a instabilidade aeroelástica em estruturas de pontes suspensas têm adquirido relevante destaque no âmbito das pesquisas em engenharia do vento nos últimos anos, haja vista que as definições resultantes dessa análise apresentam informações essenciais ao projeto, cálculo e concepção desse tipo de estrutura. Considerando que os escoamentos ao redor de pontes suspensas apresentam características turbulentas, o conhecimento acerca desse fenômeno torna-se fundamental para a análise da interação vento-ponte, estabelecendo a turbulência como uma importante e complexa vertente dentro dessa pesquisa. Nesse contexto, o presente trabalho visa contribuir com o tema através da análise numérica da ação do vento na seção transversal do tabuleiro de pontes suspensas, verificando seu comportamento quando estiverem submetidas à ação dos esforços provenientes do vento na interação de um escoamento turbulento com o tabuleiro da ponte. No trabalho foi investigada a atuação dos esforços aerodinâmicos na estrutura da ponte, ensejando na obtenção dos coeficientes aerodinâmicos de arrasto, sustentação e momento. Também foi analisado o comportamento do tabuleiro para o surgimento das vibrações induzidas por vórtices, permitindo o cálculo da frequência de desprendimento de vórtices e determinação do número de Strouhal. No que tange aos esforços aeroelásticos para o estudo específico do drapejamento (flutter), foram avaliadas as amplitudes de deslocamentos torcionais para o cálculo e obtenção da velocidade crítica do vento que acarreta o fenômeno do flutter. Juntamente com as análises aerodinâmicas e aeroelásticas da seção transversal da ponte, diferentes modelos de turbulência foram aplicados nas simulações para se estabelecer uma análise comparativa entre os escoamentos. As simulações computacionais desenvolvidas e apresentadas neste trabalho foram realizadas com auxílio de um programa de CFD (Computational Fluid Dynamics). Os modelos de ponte utilizados no trabalho foram o da ponte suspensa Great Belt East, localizada na Dinamarca e da ponte estaiada Sunshine Skyway, localizada nos Estados Unidos. Para validação da técnica computacional, os resultados das simulações foram comparados com dados numéricos e experimentais disponíveis na literatura. / Researches about aeroelastic instability in long span suspension bridges have been consistently the focus in wind engineering field in recent years, therefore the definitions from that study present essential information to design and construction of this type of road structure. Considering that fluid flows around bridges show some turbulent features, the knowledge about turbulence become critical for this wind-bridge interaction analysis, establishing the turbulence modeling study as an important and complex part within that research. According to this context, the meaning of this research was to contribute with numerical analysis of wind effects on a suspension bridge deck, verifying its behavior when this model is subjected to the action of wind loads from a turbulent fluid flow. The bridge aerodynamic behaviour was investigated and aerodynamic coefficients of drag, lift and moment were calculated. Flow induced vibrations were also analyzed for the bridge deck model, allowing it to obtain the vortex shedding frequency and Strouhal number. With regard to aeroelasticity and focusing on flutter study, the amplitudes of torsional displacements were evaluated as well as the analysis of critical wind velocity that causes flutter instabilities. Along with aerodynamic and aeroelastic analysis of the bridge deck cross sectional, fluid flow features were studied and compared applying several turbulence models to simulations. The numerical approach developed and shown in this work was performed by CFD (Computational Fluid Dynamics) software. The bridge deck models used at this dissertation were the Great Belt East suspension bridge, located in Denmark and the Sunshine Skyway cable stayed bridge, located in USA. In order to validate the computational technique, simulation results from this research were compared with numerical and experimental test data available in papers and literature.

Ce travail de thèse se propose de déterminer la distribution de vitesse dans des canaux composés à travers une étude expérimentale et numérique. Afin de répondre à cette problématique, deux approches sont suivies répondant chacune à des enjeux scientifiques et techniques et sous la contrainte de verrous scientifiques. La première approche est une étude expérimentale dont le but est de combler le manque de connaissances sur la distribution de vitesse dans des canaux type réseaux. Une série d’expérimentations est effectuée dans le hall expérimental de l’équipe mécanique des fluides du laboratoire ICube. La deuxième approche est la modélisation 3D où il s’agit de modéliser les travaux de (Proust et al., 2013) pour en déduire la distribution de vitesse dans une section transversale. Cette deuxième approche a pour but de développer une méthodologie de modélisation 3D du champ de vitesse en canaux composés. En plus des modèles de turbulence classiques (Kepsilon, K-oméga, RSM …); la simulation des grandes échelles est utilisée. Les résultats obtenus numériquement seront ensuite comparés à des données expérimentales. Les deux approches suivies dans cette thèse s’autoalimentent : l’étude expérimentale construit une base de données servant à valider le modèle numérique alors que l’étude numérique permet d’étendre les résultats des expérimentations à d’autres géométries. / Compound channels are characterized by a main channel and a floodplain. Their hydraulic behavior has important applications in rivers and flood control but also in sewer system management. Two approaches are followed in this study. The first one is an experimental study that aims to fulfill the lack of data concerning velocity distribution in narrow and deep compound channels. The experiments were carried out in a 16m long and 0.6m wide compound channel located in the experimental hall of ICube laboratory. The second approach is a numerical one. The objective of this study is to develop a methodology for numerical modelling of velocity distribution in compound channels. To do the experimental data of (Proust et al., 2013) were modelled compared to the experimental data in order to determine the most suitable model to reproduce velocity distribution. In addition to this comparison, the large eddy simulation method were also utilized for two experiments of (Proust et al., 2013) and (Nezu et al., 1990). Two specific boundary conditions were implemented in order to compare the efficiency of each method.

The reliable prediction of turbulent non-equilibrium flows is of high academic and industrial interest in several engineering fields. Most turbulent flows are often predicted using single-time-scale Reynolds-Averaged-Navier-Stokes (RANS) turbulence models which assume the flows can be modelled through a single time or length scale which is an admittedly incorrect assumption. Therefore they are not expected to capture the lag in the response of the turbulence in non-equilibrium flows. In attempts to improve prediction of these flows, by taking into consideration some features of the turbulent kinetic energy spectrum, the multiple-time-scale models arose. A number of two-scale models have been proposed, but so far their use has been rather limited.This work thus focusses on the development of two-time-scale approaches. Two two-time-scale linear-eddy-viscosity models, referred to as NT1 and NT2 models, have been developed and the initial stages of the development of two-time-scale non-linear-eddy-viscosity models are also reported. The models' coefficients have been determined through asymptotic analysis of decaying grid turbulence, homogeneous shear flows and the flow in a boundary layer in local equilibrium. Three other important features of these models are that there is consistent partition of the large and the small scales for all above limiting cases, model sensitivity to the partition and production rate ratios and sensitivity of the eddy viscosity sensitive to the mean strain rates.The models developed have been tested through computations of a wide range of flows such as homogeneous shear and normally strained flows, fully developed channel flows, zero-pressure-gradient, adverse-pressure-gradient, favourable-pressure-gradient and oscillatory boundary layer flows, fully developed oscillatory and ramp up pipe flows and steady and pulsated backward-facing-step flows.The proposed NT1 and NT2 two-scale models have been shown to perform well in all test cases, being, among the benchmarked models tested, the models which best performed in the wide range of dimensionless shear values of homogeneous shear flows, the only linear-eddy-viscosity models which predicted well the turbulent kinetic energy in the normally strained cases and the only models which showed satisfactory sensitivity in predicting correctly the reattachment point in the unsteady backward facing step cases with different forcing frequencies. Although the development of the two-time-scale non-linear-eddy-viscosity models is still in progress, the interim versions proposed here have resulted in predictions of the Reynolds normal stresses similar to those of much more complex models in all test cases studied and in predictions of the turbulent kinetic energy in normally strained flows which are better than those of the other models tested in this study.

[ES] El objetivo de esta tesis es la investigación y análisis de la estructura interna de los chorros diésel reactivos y el efecto de las condiciones de contorno en los parámetros asociados a la combustión. Este objetivo se consigue por medio de la simulación numérica del chorro con modelos de turbulencia RANS y LES usando un modelo de combustión avanzado basado en el concepto flamelet. Para este estudio, se aplica una aproximación simplificada de las flamelets de difusión, conocidas en la literatura como Flamelets de Difusión Aproximadas (ADF en inglés), como fundamento del modelo de combustión. En una primera etapa, el modelo se valida con combustibles de diferente complejidad química en regímenes estacionarios y transitorios para el conjunto de posibles velocidades de deformación. Una vez se confirma su idoneidad para condiciones encontradas en chorros diésel, se aplica a la simulación del chorro A del Engine Combustion Network (ECN), representativo de chorros diésel. Para proporcionar un cuadro completo de los fenómenos subyacentes, la combustión se analiza inicialmente para condiciones homogéneas y llamas laminares para las distintas condiciones de contorno de este experimento. Después este análisis se complementa con la simulación de diferentes mecanismos químicos para determinar cómo las características del encendido predichas por el esquema de oxidación afectan a la propagación de llama. Los resultados obtenidos en esta etapa se enlazan con el análisis del chorro turbulento en el contexto de simulaciones RANS y LES para describir cómo el fenómeno de la combustión se modifica con los diferentes niveles de complejidad física. La estructura del chorro turbulento se describe profundamente para las distintas condiciones de contorno y mecanismos químicos en términos de mezcla y escalares reactivos para las fases temporales y las regiones espaciales de la llama. La satisfactoria concordancia con los resultados experimentales muestran que el concepto flamelet, y más particularmente el modelo ADF, es adecuado para las simulaciones de chorros diésel. / [CAT] L'objectiu d'esta tesi és la investigació i anàlisi de l'estructura interna dels dolls dièsel reactius i l'efecte de les condicions de contorn en els paràmetres associats a la combustió. Este objectiu s'aconsegueix per mitjà de la simulació numèrica del doll amb models de turbulència RANS i LES usant un model de combustió avançat basat en el concepte flamelet. Per a este estudi, s'aplica una aproximació simplificada de les flamelets de difusió, conegudes a la literatura com Flamelets de Difusió Aproximades (ADF en anglés), com a fonament del model de combustió. En una primera etapa, el model es valida amb combustibles de diferent complexitat química en règims estacionaris i transitoris per al conjunt de possibles velocitats de deformació. Una vegada es confirma la seua idoneïtat per a condicions trobades en dolls dièsel, s'aplica a la simulació del doll A del Engine Combustion Network (ECN), representatiu de dolls dièsel. Per a proporcionar un cuadre complet dels fenòmens subjacents, la combustió s'analitza inicialment per a condicions homogènies i flames laminars per a les distintes condicions de contorn d'aquest experiment. Després esta anàlisi es complementa amb la simulació de diferents mecanismes químics per a determinar com les característiques de l'encesa predites per l'esquema d'oxidació afecten la propagació de flama. Els resultats obtinguts en esta etapa s'enllacen amb l'anàlisi del doll turbulent en el context de simulacions RANS i LES per a descriure com el fenomen de la combustió es modifica amb els diferents nivells de complexitat física. L'estructura del doll turbulent es descriu profundament per a les distintes condicions de contorn i mecanismes químics en termes de mescla i escalars reactius per a les fases temporals i les regions espacials de la flama. La satisfactòria concordança amb els resultats experimentals mostren que el concepte flamelet, i més particularment el model ADF, és adequat per a les simulacions de dolls dièsel. / [EN] The objective of this thesis is the investigation and analysis of the internal structure of diesel-like reacting sprays and the effect of boundary conditions on combustion related parameters. This objective is achieved by means of the numerical simulation of the spray with RANS and LES turbulence models using an advanced combustion model based on the flamelet concept. For this study, a simplified approach for diffusion flamelets, known in the literature as Approximated Diffusion Flamelet (ADF), is applied as the basis of the combustion model. In a first step, this model is validated for fuels with different chemical complexity in steady and transient regimes for the whole set of possible strain rates. Once its suitability is confirmed for conditions found in diesel sprays, it is applied to the simulation of spray A from the Engine Combustion Network (ECN), representative of diesel-like sprays. In order to provide a complete picture of the underlying phenomena, combustion is initially analysed in homogeneous conditions and laminar flames for the different boundary conditions of this experiment. Later, this analysis is complemented with the simulation of different chemical mechanisms in order to determine how the ignition characteristics predicted by the oxidation scheme affect to the flame propagation. The results obtained at this stage are connected with the analysis of the turbulent spray in the context of RANS and LES simulations as a way to track how combustion phenomenon is modified at the different levels of physical complexity. The turbulent spray structure is thoroughly described for the different boundary conditions and chemical schemes in terms of mixing and reactive variables for both temporal phases and spatial flame regions. The satisfactory agreement with experimental results shows that the flamelet concept, and more particularly the ADF model, is suitable for diesel-like sprays simulations. / Pérez Sánchez, EJ. (2019). Application of a flamelet-based combustion model to diesel-like reacting sprays [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/117316 / TESIS

Liquid waste discharged from industrial outfalls is categorized into two major classes based on their density. One type is the effluent that has a higher density than that of the ambient water body. In this case, the discharged effluent has a tendency to sink as a negatively buoyant jet. The second type is the effluent that has a lower density than that of the ambient water body and is hence defined as a (positively) buoyant jet that causes the effluent to rise. Negatively/Positively buoyant jets are found in various civil and environmental engineering projects: discharges of desalination plants, discharges of cooling water from nuclear power plants turbines, mixing chambers, etc. This thesis investigated the mixing and dispersion characteristics of such jets numerically. In this thesis, mixing behavior of these jets is studied using a finite volume model (OpenFOAM). Various turbulence models have been applied in the numerical model to assess the accuracy of turbulence models in predicting the effluent discharges in submerged outfalls. Four Linear Eddy Viscosity Models (LEVMs) are used in the positively buoyant wall jet model for discharging of heated waste including: standard k-ε, RNG k-ε, realizable k-ε and SST k-ω turbulence models. It was found that RNG k-ε, and realizable k-ε turbulence models performed better among the four models chosen. Then, in the next step, numerical simulations of 30˚ and 45˚ inclined dense turbulent jets in stationary ambient water have been conducted. These two angles are examined in this study due to lower terminal rise height for 30˚ and 45˚, which is very important for discharges of effluent in shallow waters compared to higher angles. Five Reynolds-Averaged Navier-Stokes (RANS) turbulence models are applied to evaluate the accuracy of CFD predictions. These models include two LEVMs: RNG k-ε, and realizable k-ε; one Nonlinear Eddy Viscosity Model (NLEVM): Nonlinear k-ε; and two Reynolds Stress Models (RSMs): LRR and Launder-Gibson. It has been observed that the LRR turbulence model as well as the realizable k-ε model predict the flow more accurately among the various turbulence models studied herein.

Os processos oxidativos avançados são promissores para a degradação de compostos orgânicos resistentes aos tratamentos convencionais, como o fenol. A fluidodinâmica computacional (CFD) tornou-se uma poderosa ferramenta para analisar processos fotoquímicos por resolver os balanços acoplados de quantidade de movimento, de massa e de radiação. O objetivo deste trabalho é investigar o processo UV/H2O2 num reator fotoquímico anular usando CFD e um modelo cinético mais realista. O modelo em CFD foi criado de forma progressiva. Inicialmente, foram determinados os campos de velocidade para três vazões (30, 60 e 100 L/h). Considerou-se dois diâmetros de lâmpada para reproduzir a configuração experimental do sistema. A discretização foi feita com malhas tetraédricas variando entre 390 000 e 1 200 000 elementos. Quatro modelos de turbulência RANS foram analisados: k-e, k-w, o shear stress transport (SST) e o modelo de tensões de Reynolds (RSM). O campo de velocidades foi validado comparando a DTR com seu levantamento experimental. A próxima etapa foi incluir o mecanismo de degradação de fenol proposto por Edalatmanesh, Dhib e Mehrvar (2008) no modelo em CFD. Trata-se de um modelo cinético baseado em equações dinâmicas para todas as espécies. O campo de radiação foi calculado pelo modelo radial e pela solução da equação de transporte de radiação através do método discrete transfer. As simulações reproduziram dados experimentais abrangendo uma larga gama de concentrações iniciais de fenol, razões molares H2O2/fenol e três potências de emissão das lâmpadas. O campo de velocidades obtido era dependente da vazão: o fluido pode manter movimento helicoidal sobre toda a extensão do reator ou se desenvolver como um escoamento pistonado. O modelo k-e não reproduziu bem o escoamento por não ser adequado para escoamentos rotativos. Os outros modelos geraram curvas de DTR com bom ajuste aos dados experimentais, especialmente o modelo k-w. O desvio médio entre as simulações de degradação de fenol e os dados experimentais é inferior a 8%. Verificou-se que, devido ao escoamento rotativo, os reagentes ficavam concentrados próximos à parede externa e migravam para a região da lâmpada ao longo do reator. A elevada intensidade de radiação na superfície da lâmpada criou uma camada ao seu redor na qual a fotólise do H2O2 ocorreu com grande taxa. Os radicais OH gerados nessa camada eram transportados para a região das paredes por convecção. Isso fez com que a maior parte do fenol fosse atacada na segunda metade do reator e gerou acúmulo do radical próximo à lâmpada na seção de saída do reator, já que o poluente já fora oxidado nessa área. O método discrete transfer previu intensidades de radiação maiores que o modelo radial, e, consequentemente, maior concentração de radicais OH. Os resultados satisfatórios indicam que CFD foi uma ferramenta adequada para analisar este escoamento reativo. / Advanced oxidation processes are a promising technology for degradation of organic compounds resistant to conventional treatments such as phenol. Computational fluid dynamics (CFD) has recently emerged as a powerful tool that allows a deeper understanding of photochemical processes in reactor engineering by solving the coupled momentum, mass and radiation balances. This work aimed to investigate the UV/H2O2 process in an annular photoreactor using CFD and a more realistic kinetic model. A progressive approach was used to develop the CFD reactor model. First, the velocity fields were determined for three volumetric flow rates (30, 60 and 100 L/h). Two lamp diameters were considered to reflect the experimental configuration of the system. Tetrahedral meshes varying form 390,000 to 1,200,000 elements were analyzed to achieve grid independence. For accounting turbulence effects, four RANS models were tested: k-e, k-w, the Shear Stress Transport (SST) and the Reynolds Stress models (RSM). The velocity field was validated through comparison to RTD experimental data. Next step was introducing the mechanism of phenol degradation proposed by Edalatmanesh, Dhib and Mehrvar (2008) into the CFD model. This kinetic model is based on dynamic equations for all species. The fluence rate field was calculated by the radial model and by solving the radiation transport equation with the discrete transfer method. Simulations reproduced experimental data spanning a wide range of initial phenol concentrations, H2O2/phenol molar ratios and three values for lamp power. It was found that the velocity field depends on the volumetric flow rate: either it maintains a swirling motion through the whole reactor or might develop like a plug flow. The k-e model did not represent the RTD data accurately, and the velocity field therefore, since it is not appropriate for swirling flows. The other turbulence models showed good match of RTD, especially the k-w model. Simulations of phenol degradation deviated less than 8% from experimental data. It was possible verified that, due to the swirling inlet effects, reactants got concentrated close to the outer wall and migrated on the lamp direction along the reactor path. High radiation intensities close to the lamp surface created a layer around it where photolysis of H2O2 took place with higher rates. OH radicals were generated in that layer and transported towards the outer wall by convection. This caused most of phenol to be consumed in the second half of the reactor and accumulation of the radical near the lamp and the reactor outlet, since the pollutant in this area was already oxidized. The discrete transfer method predicted higher incident radiation intensity than the radial model, and higher concentrations of OH radicals as a consequence. Satisfactory results indicated that CFD was an appropriate tool for analyzing this reactive flow.

Turbulent dynamics at two sites (C and D) in a hypoxic zone on the Texas- Louisiana continental shelf were studied by investigating turbulence quantities i.e. turbulence kinetic energy (TKE), dissipation rate of TKE (E), Reynolds stress (τ ), dissipation rate of temperature variance (χ), eddy diffusivity of temperature (ν't), and eddy diffusivity of density (ν'p). Numerical models were also applied to test their capability of simulating these turbulence quantities. At site D, TKE, E, and τ were calculated from velocity measurements in the bot- tom boundary layer (BBL), using the Kolmogorov’s -5/3 law in the inertial subrange of energy spectra of vertical velocity fluctuations in each burst measurement. Four second-moment turbulence closure models were applied for turbulence simulations, and modeled turbulence quantities were found to be consistent with those observed. It was found from inter-model comparisons that models with the stability functions of Schumann and Gerz predicted higher values of turbulence quantities than those of Cheng in the mid layer, which might be due to that the former stability functions are not sensitive to buoyancy. At site C, χ, E, v’t, and ν’p were calculated from profile measurements throughout the water column, and showed high turbulence level in the surface boundary layer and BBL, as well as in the mid layer where shear stress was induced by advected non-local water above a hypoxic layer. The relatively high dissolved oxygen in the non-local water resulted in upward and downward turbulent oxygen fluxes, and the bottom hypoxia will deform due to turbulence in 7.11 days. Two of the four models in the study at site D were implemented, and results showed that turbulence energy resulting from the non-local water was not well reproduced. We attribute this to the lack of high-resolution velocity measurements for simulations. Model results agreed with observations only for χ and E simulated from the model with the stability function of Cheng in the BBL. Discrepancies between model and observational results lead to the following conclusions: 1) the stability functions of Schumann and Gerz are too simple to represent the turbulent dynamics in stratified mid layers; 2) detailed velocity profiles measurements are required for models to accurately predict turbulence quantities. Missing such observations would result in underestimation,

O presente trabalho realiza um estudo do desempenho aerodinâmico da turbina eólica de duas pás e 10 m de diâmetro da UAE Phase VI, testada pelo NREL no túnel de vento NASA Ames, através do uso de dinâmica dos fluidos computacional (CFD). Para tanto são apresentados conceitos fundamentais para análise da performance do aerogerador, a metodologia aplicada para a análise numérica e os resultados obtidos. O modelo geométrico da turbina foi inserido em ambiente computacional num domínio com as mesmas dimensões da seção de testes do túnel de vento. A esse domínio foi empregada uma malha de elementos tetraédricos. A modelagem numérica e as simulações foram efetuadas através do código comercial ANSYS FLUENT 13.0 e utilizaram as equações médias de Reynolds e modelos de turbulência k  SST e Spalart-Allmaras. A turbina simulada possui ângulo de giro (yaw) e de cone de 0°. Os casos simulados foram de turbina com ângulos de passo das pás de 0° e 3°, para velocidades de ar na entrada do domínio de 5 m/s, 7 m/s e 9 m/s. As simulações foram feitas em regime transiente utilizando o método de malha móvel. Dados provenientes da simulação numérica são comparados aos dados experimentais de empuxo, torque e potência, divulgados pelo laboratório. Os modelos de turbulência testados apresentaram boa concordância com os resultados experimentais de empuxo. O torque e a potência foram bem previstos para velocidades de entrada do domínio baixas, mas foram subdimensionados para velocidades mais altas. A separação da camada limite foi prevista por ambos os modelos. Na comparação com resultados obtidos com outros autores para o mesmo caso, o início de descolamento da camada limite se deu antes do previsto. A metodologia adotada nas simulações numéricas realizadas mostrou-se adequada e representativa nas análises desse estudo. / This study makes a CFD analysis of the aerodynamic performance of the NREL UAE Phase VI two-bladed wind turbine, which have been tested in the NASA Ames wind tunnel. Fundamental concepts on the evaluation of turbine performance, the applied methodology for the numerical analysis and the results are presented. A numerical model has been inserted in a computational environment that has the same dimensions as the real wind tunnel section, and a tetrahedral mesh has been created to fill this domain. Numerical modeling and the simulations have been performed using the ANSYS FLUENT 13.0 commercial code, making use of the RANS equations and the k  SST and Spalart-Allmaras turbulence models. The simulated turbine has 0 degrees of cone and yaw angle. Simulations were performed in unsteady state using the moving mesh technique. Results are compared to experimental data regarding to thrust, torque and power. The k  SST and Spalart-Allmaras turbulence models have shown good agreement with experimental values of thrust. Torque and power have been adequately predicted to lower free flow velocities, but have been underpredicted to higher velocities. Separation of the boundary layer has been adequately predicted by both models, but the beginning of the separation occurred earlier than expected in comparison with results of other authors to the same case. The methodology used in the numerical simulations proved to be adequate and representative in this study.

This thesis presents the development of a novel numerical model capable of evaluating suspended sediment dynamics under breaking waves, and is based in the open source Computational Fluid Dynamics software, OpenFOAM®. The hydrodynamics were determined by solving the incompressible, Reynolds-Averaged Navier-Stokes equations for a two-phase fluid using the Finite Volume method, along with a Volume of Fluid scheme that modelled the interface between the air and water phases. A new library of five turbulence models was developed to include weakly compressible effects through the introduction of density variations in the conservation equations. This library was thoroughly evaluated against existing physical data for surf zone dynamics. A skill score was applied, based on the MSE, to rank the models, with the nonlinear k−ε performing best overall, and the k−ω predicting turbulent kinetic energy most accurately. Furthermore, the numerical model was shown to predict the near-bed hydrodynamics well, through comparison with new in-house physical data obtained in the COAST laboratory. Suspended sediment concentrations were determined using an advection-diffusion methodology, with near-bed processes modelled using a flux based approach that balances entrainment and deposition. The model was validated against existing experimental data for steady state flow conditions, as well as for regular and breaking waves. The agreement was generally good, with the results indicating that the model is capable of capturing complicated processes such as sediment plumes under plunging breakers. The validated model was applied to investigate the properties of the sediment diffusivity, which is a vital parameter in suspended sediment dynamics. In physical experiments, sediment diffusivity is commonly estimated implicitly, based on the vertical concentration profile. In this work, this approach was applied to the numerical concentration predictions, and compared with the value directly determined within the model. The estimated value was generally acceptable providing that large horizontal concentration gradients were not present, and diffusion dominated flow advection. However, near the breaking point of waves, large errors were observed at mid-depth of the water column, which strongly correlates with a region of large flow advection relative to diffusion. Therefore, when using this estimation, caution is recommended since this approach can potentially lead to substantial discrepancies.

Made available in DSpace on 2014-06-11T19:23:38Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-12-20Bitstream added on 2014-06-13T19:47:44Z : No. of bitstreams: 1 souza_eg_me_ilha.pdf: 959550 bytes, checksum: b4784dbcc883b1be2d0c6b7cce83f54b (MD5) / Fundação de Ensino Pesquisa e Extensão de Ilha Solteira (FEPISA) / O objetivo deste trabalho é a análise numérica e experimental de escoamento viscoso, incompressível, permanente, com transferência de calor, em um canal estreito contendo um arranjo de obstáculos retangulares. A análise experimental envolveu determinação de coeficiente de transferência de calor médio bem como o número de Nusselt médio e medidas de temperatura em esteira térmica para comparação com os resultados obtidos por simulação numérica. Para a análise numérica usamos o programa comercial de mecânica dos fluidos e transferência de calor computacional ICEPAK®. Verificamos que quanto mais adentro o obstáculo estiver no arranjo maior é a transferência de calor por convecção forçada. Determinamos coeficientes de transferência de calor médio e número de Nusselt médio (com incerteza entre 6 e 15%) e verificamos que o efeito da posição diminui à medida que a velocidade aumenta. Concluímos também que ambos os modelos de turbulência utilizados, k-ε padrão e k-ε RNG, foram incapazes de predizer o efeito da posição apropriadamente. Entretanto, o modelo k-ε RNG apresentou melhor comportamento, pois o seu uso resultou em soluções com valores de temperatura intermediários aos experimentais / The purpose of this work is the study of the numerical and experimental viscous incompressible steady flow with heat transfer into a narrow channel containing a rectangular array of obstacles. The experimental approach involves determining the coefficient of heat transfer and temperature measurements in thermal wake for comparison with the results obtained in numerical simulations. For the numerical analysis we use the commercial program of fluid mechanics and heat transfer computational ICEPAK™. We confirmed that in the last lines of the array the biggest is the heat transfer by forced convection. We determined the average heat transfer coefficients (with uncertainty between 6 and 15%) and found that the effect of the position decreases as flow speed increases. We use in the simulations the k-ε turbulence model and the k-ε RNG turbulence model. We conclude that both turbulence models used were unable to predict the effect of the position properly. However, the k-ε RNG model showed better behavior. The numerical temperatures with this model were consistent to the experimental temperature