Com os grandes avanços ocorridos na disponibilização de computadores, existe uma tendência contínua para a utilização de técnicas computacionais auxiliando no projeto de equipamentos de engenharia. Cada vez mais estão se obtendo resultados bastante próximos às condições reais, incluindo a simulação de motores de combustão interna. Neste sentido o presente trabalho tem o objetivo de analisar o escoamento turbulento no processo de admissão de ar em um motor operando em ciclo Diesel. A investigação é focada na determinação da influência do passo de tempo no cálculo do coeficiente de descarga e razão de swirl. Adicionalmente, o campo de velocidades, pressão, energia cinética turbulenta e outros parâmetros são apresentados e analisados, com o objetivo de auxiliar no entendimento da dinâmica envolvida. Essencialmente, dois modelos de turbulência são empregados, juntamente com dois tratamentos de parede. Seus resultados também são confrontados e discutidos. A geometria considerada é de um motor Fiat 1.9 L quatro tempos com duas válvulas. A análise é concentrada em um único cilindro. O pacote computacional utilizado é o Star-cd, e seu aplicativo es-ice. A independência de malha foi obtida, chegando a 1.672.056 volumes. Os resultados são apresentados de duas formas. A primeira delas refere-se a resultados de simulações em regime permanente, realizadas em boa parte por outros autores, com ênfase na determinação do coeficiente de descarga e razão de swirl, estes confrontados com valores experimentais, visando à validação da metodologia. Fica evidente a importância da escolha do modelo de turbulência na simulação de motores de combustão interna, assim como das funções de interpolação utilizadas. Na segunda parte os resultados referem-se a uma análise transiente, considerando o movimento do pistão e válvulas, a 1500 RPM. Observa-se a grande exigência quanto ao passo de tempo requerido no transiente real, ficando demonstrado que para esta velocidade o menor passo de tempo utilizado, 0,05° (5.5555E-6 s), ainda é insuficiente para alguns momentos do ciclo. É possível notar maior influência no coeficiente de descarga do que na razão de swirl, em relação aos passos de tempo utilizados. A forte dependência do modelo de turbulência nos resultados obtidos é mais uma vez confirmada, conforme o esperado, já que as hipóteses sobre a física do fenômeno são diferentes em cada modelo. Os resultados quanto ao tratamento na parede não apresentaram significantes diferenças, quando aplicados junto ao modelo de turbulência k-ω SST. / Considering the increase in the availability of computers, there is a continuing trend toward the use of computational simulation aiding in the design of engineering equipments. Reasonable results, close to the real conditions, are obtained, including the simulation of internal combustion engines. In this way, the present work has the objective of analyzing the turbulent flow in the air intake process of an engine operating in Diesel cycle. The investigation focuses on the determination of the time step in the calculation of the air discharge coefficient and swirl ratio. Additionally, the turbulent kinetic energy, pressure and velocity fields, besides other parameters, are presented and analyzed, with the objective of aiding in the understanding of the involved dynamics. Essentially, two turbulence models are employed, together with two wall treatments. Their results are also confronted and discussed. The considered geometry is a four-stroke, 1.9-L FIAT engine, with two valves. The analysis is concentrated on a single cylinder. The software package used is the Star-cd, and its application es-ice. The mesh independence is carried out, arriving in 1.672.056 volumes. The results are presented in two ways. The first one refers to simulation results of the steady state, also accomplished by other authors, with emphasis in the determination of the discharge coefficient and swirl ratio. These data are confronted with experimental values, aiming to validate the applied methodology. The importance of the choice of the turbulent model becomes evident in the simulation of internal combustion engines, as well as the interpolation functions used. In the second part the results refer to a transient analysis, considering the valves and piston movement, at 1500 rpm. It is observed the great demand on time step required is observed for the real transient, demonstrating that, for this speed, the smallest time step used, 0.05º (5.5555E-6 s), is still insufficient for some moments of the cycle. Also regarding the time step, it is possible to notice a greater influence in the discharge coefficient than in the swirl ratio. The strong dependence of the turbulence model on the results is once again confirmed, as expected, since the hypotheses about the physics of the phenomenon are different in each model. The results, regarding the wall treatment, presented no significant differences, when applied together with the SST k-ω turbulence model.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Realizou-se o levantamento de curvas de eficiÃncia utilizando odelos numÃricos RANS de uma e duas equaÃÃes para um erogerador com 3m de diÃmetro, utilizando pÃs projetadas para operar em diferentes condiÃÃes de λ com perfis NACA 0012, 4412 e 6412. A parametrizaÃÃo da geometria da malha para a dimensÃo do rotor, juntamente com a parametrizaÃÃo do refinamento frente à capacidade dos modelos RANS obteve a independÃncia da malha à soluÃÃo. Posteriormente a anÃlise numÃrica realizou a comparaÃÃo do melhor resultado â pà projetada λ=6 com o perfil NACA 6412 â com dados experimentais. O aparato experimental foi capaz de coletar dados de rotaÃÃo e torque do rotor simultaneamente com a mediÃÃo da velocidade do vento, no qual foi obtido um valor mÃximo de eficiÃncia de aproximadamente 25% e uma faixa de operaÃÃo limitada a λ=6. Conclui-se que os modelos fornecem boa precisÃo em predizer a faixa operacional de λ, no entanto os valores de Cp foram subestimados. O modelo k-ω SST apresentou o melhor resultados dentre todos. / A survey was conducted, consisting of efficiency curves applying RANS turbulence numerical models of one and two equations for a wind turbine with a diameter of 3m, using blades designed to operate under different λ with NACA 0012, 4412 and 6412 profiles. The parameterization of the mesh geometry to the size of the rotor, together with the parameterization of the refinement level compared to the ability of RANS models reached independence from the grid to the solution. Later, a numerical analysis was performed to compare the best result â a blade designed to operate under λ = 6 with the NACA 6412 profile - against experimental data. The experimental apparatus was able to collect data rotation and torque of the rotor simultaneously with the measurement of wind velocity, which obtained a maximum efficiency of approximately 25% and an operating range limited to λ = 6. It can be concluded that the models provide good accuracy in predicting the operating range of λ, however the values of Cp were underestimated. The k-ω SST model showed the best results among all.

The aim of this paper is to investigate using of hybrid turbulence models for strongly swirling flows. The work is focused on the possibility of applying a hybrid SBES model to simulate flow around a hydrofoil. The work further describes the creation of a mesh for the solved domain, the setting of boundary conditions and the setting of the solution for the software FLUENT. The simulation results are compared with experimentally measured values. The work also uses and evaluates data from PIV measurements. The knowledge that the paper brings as part of the results of a research project can be applied in the future in the design of blades of water turbines.

This Diploma thesis deals with CFD simulations of flow around vehicles subjected to a crosswind with MIRA Reference Car in three body shapes with a diffuser serving as a vehicle. It contains tuning of computational grid and chosen solver settings in Fluent, mostly for v2f turbulence model. The main output of this thesis is a simulation of all body shapes in several crosswind angles in steady state and one chosen body shape with one chosen crosswind angle in unsteady state. All results are validated against measurements taken with full scale models in MIRA windtunnel.

The present study utilizes the relational turbulence model (RTM) to illuminate stepparent experiences of relational uncertainty and partner interference within the context of the stepparent-biological parent marriage. In-depth, semi-structured interviews with 6 stepparents revealed four primary themes pertaining to how stepparents experienced relational uncertainty: (a) enactment of parenting, (b) competing expectations, (c) shifts in attitude and behavior by spouse, and (d) differences between marriage partners. Interference from partners was experienced by stepparents in relation to the enactment of parenting and the maintaining of the marriage as an intimate relationship.

Finite Element computer codes in two and three dimensions were written that solve both laminar and turbulent flow. These codes use the two equation (k and E) turbulence model to evaluate turbulent viscosity. They were tested with 29 different flow problems. The largest two dimensional turbulent problem solved is flow under a sluice gate. A three dimensional vortex flow problem was attempted but was not feasible due to the size of the available computer. The Harwell sparse matrix subroutines of the United Kingdom Atomic Energy Authority were used to solve the set of simultaneous equations. The performance of these subroutines is evaluated. The importance of defining adequate finite element grids and setting proper boundary and initial conditions is discussed.

A turbulence model was developed for computing surface velocity coefficients and discharge under steady, uniform flow conditions for rectangular and compound open-channel cross sections. Reynolds-Average Navier-Stokes (RANS) equations, Reynolds stress equations, and kinetic energy and dissipation equations were applied in the model using the finite-volume method with the SIMPLER algorithm. The models show graphical results of the velocity distributions in the longitudinal bed slope direction, secondary velocities, pressure, turbulence kinetic energy, and kinetic energy dissipation rate across the cross section. Also, the surface velocity coefficients were computed at increments of one-eighth of the base width from the vertical walls to the center of the cross section, and the submergence depth of the floating object from zero to 30 cm, with a 5-cm depth increment. Four different sets of Reynolds stress equations (one set by Boussinesq hypothesis and three sets of algebraic stress model) were used to calculate the results. Only one version of the algebraic stress model was successful in predicting the depression of the maximum streamwise velocity below the water surface. The model was calibrated and verified using laboratory data collected at Utah State University. Calculated discharges from the turbulence model had very good agreement with the laboratory data. The surface velocity coefficients from model results were generally lower than the results from the laboratory data, but higher than the values published by the United States Bureau of Reclamation. Standard cross sections of rectangular and compound cross sections were defined to simulate the model results and model sensitivity to parameter changes. The model results were summarized to show the relationship between surface velocity coefficient and channel characteristics compared with the published values by the USBR. For rectangular cross sections, the coefficients from the model are higher than the published USBR values. But the coefficients from the model and USBR are in very close agreement for the tested compound cross sections. The published coefficients by the USBR are a function of only average water depth. However, the model results show that the coefficients are also related to channel size, surface roughness height, float submergence depth, and lateral location of the float object. These factors should be included in the determination of the surface velocity coefficient to improve the discharge estimations from the application of the float method.

Wind resource assessment at California Polytechnic State University shows there is potential for wind power generation on Cal Poly land. A computational fluid dynamics model based on wind data collected from a campus maintained meteorological tower on Escuela Ranch approximately 5 miles northwest of campus suggests there are areas of Cal Poly land with an IEC Class III wind resource at a height of 80 meters above ground. In addition during the daytime when the campus uses the most energy there are large portions of land with annual average daytime wind speeds above 6.9m/s. These areas have been identified by analyzing the wind speed and directional data collected at the meteorological tower and using it to create the boundary conditions and turbulence parameters for the computer model. The model boundary conditions and turbulence parameters have been verified through comparison between data collected at Askervein hill in Scotland during the 1980’s and the results of a simulation of Askervein hill using the same model. Before constructing a wind farm for power generation, additional meteorological towers should be constructed in Poly Canyon to further confirm the wind resource prediction.

No / Nazarbayev University Seed Grant, entitled “Environmental assessment of sediment pollution impact on hydropower plants”.

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