The main motivation of this thesis is the analysis of turbulent flows. Turbulence plays an important role in engineering applications due to the fact that most flows in industrial equipment and surroundings are in turbulent regime. The thesis has a double purpose and is divided in two main parts. The first one is focussed on the basic and fundamental analysis of turbulence models. In the second part the know-how acquired in the first part is applied to the study of air curtains.Regarding to the first part, the principal difficulty of computing and modelling turbulent flows resides in the dominance of non-linear effects and the continuous and wide spectrum of time and length scales. Therefore, the use of turbulence modelling employing statistical techniques for high Reynolds numbers or complex geometries is still necessary. In general, this modelization is based on time averaging of the Navier-Stokes equations (this approach is known as Reynolds-Averaged Navier-Stokes Simulations, RANS). As consequence of the average new unknowns, so-called Reynolds stresses, arise. Different approaches to evaluate them are: i) Differentially Reynolds Stress Models (DRSM), ii) Explicit Algebraic Reynolds Stress Models (EARSM), and iii) Eddy Viscosity Models (EVM).Although EVM models assuming a linear relation between the turbulent stresses and the mean rate of strain tensor are extensively used, they present various limitations. In the last few years, with the even-increasing computational capacity, new proposals to overcome many of these deficiencies have started to find their way. Thus, algebraic or non-linear relations are used to determinate the Reynolds stress tensor without introducing any additional differential equation.Therefore, the first part of this thesis is devoted to the study of several EARSM and EVM models involving linear and higher order terms in the constitutive relation to evaluate turbulent stresses. Accuracy and numerical performance of these models is tested in different flow configurations such as plane channel, backward facing step, and both plane and round impinging jets. Special attention is paid to the verification of the code and numerical solutions, and the validation of the mathematical models used. In the impinging plane configuration, improvements of models using higher order terms in the constitutive relation are limited. Whereas, in the rest of studied cases these non-linear models show a reasonably good behaviour.Moreover, taken into account models convergence, robustness and predictive realism observed in the analysis of these benchmark flows, some of them are selected for the study of air curtains and their interaction with the environment where they are placed. Air curtains are generally one or a set of vertical or horizontal plane jets used as ambient separator of adjacent areas presenting different conditions. The jet acts as a screen against energy losses/gains, moisture or mass exchanges between the areas.As was indicated before, the main purpose of the second part of this thesis is to characterize in detail actual air curtains using both experimental and different numerical approaches. Semi-empirical models to design air curtains are presented. Then, an experimental set-up used to study air curtain discharge and jet downstream is explained. Experimental measurements of velocity and temperature are shown. As a result of the experiments carried out, an improved air curtain with a new design of the discharge nozzle is obtained. Furthermore, air curtain experiments are numerically reproduced and predictions validated against the experimental data acquired. Good agreement between numerical and experimental results is observed.Finally, systematic parametric studies of air curtains in heating and refrigeration applications are done. Global energetic balances are specially considered together with global parameters selected in order to evaluate air curtain performance. It is found that discharge velocity, discharge angle and turbulence intensity of the jet are the most sensitive parameters. Inadequate values for these variables can produce undesirable effects and contribute to increase energy gains/losses.

The harsh winter conditions on the Canadian prairies impose special challenges in providing acceptable environmental conditions for broiler chickens during transportation. A research program was developed aiming to improve the transport conditions for broilers. As part of the research program, a research project was developed to design and construct an experimental trailer equipped with active ventilation and heating, to characterize the performance of the experimental trailer in field tests under Canadian Prairie winter conditions, to develop, calibrate and validate CFD models used for simulating the environmental conditions found inside the experimental trailer, and to utilize one of the CFD models to predict the performance of the experimental trailer when subjected to different operational conditions. This dissertation consists of six chapters. The first introductory chapter reviews economical, logistical and legislative aspects surrounding the poultry transport industry. This chapter also includes a discussion of important parameters for the design of an experimental transport system, a review of fundamental concepts of the Computational Fluid Dynamics (CFD) modeling method, and why CFD was chosen as a tool to complement the experimental work in this project. The second chapter reviews the designs of commercial poultry transport equipment and how they inspired the design of an actively heated and ventilated experimental vehicle. The setup of the experimental trailer was also discussed in detail. The third chapter reviews the experimental protocol used to evaluate the performance of the experimental trailer. The performance of this experimental trailer was evaluated in a series of field tests conducted under commercial loading operations, in winter conditions on the Canadian Prairies. It was found that the average load temperature varied from 7.1 to 15.6°C in the nine sts of data. The system was able to maintain an environment above 1°C. As for the humidity level inside the trailer, the majority of sensors had representative relative humidity (RH*) values between 10 and 40%, with the rest having RH* values below saturation. The fourth chapter reviews the development, calibration and validation of the 3-D CFD models developed to simulate the environmental conditions inside the experimental trailer. A total of three CFD models were developed to simulate the three different ventilation regimes encountered in field tests. Sensitivity studies revealed that inlet velocities, heat and moisture production had a great impact on the results obtained from the CFD models. The levels of porosity investigated did not play a significant role. The standard error of estimate was selected as a statistical measure to evaluate the accuracy of the CFD models against experimental data. For temperature data, its standard error of estimate varied from 3.2 to 7.3°C. For humidity ratio, its standard error of estimate varied from 1.7 to 5.0 g of water vapour per kg of dry air. The CFD models were able to recreate the temperature trends as observed from experimental data. It was concluded that these CFD models have adequate accuracy to be used as a design tool for comparative studies. The fifth chapter investigates the use of the 1-fan CFD model to study several scenarios. Three cases were investigated, based on conditions which may be encountered by the poultry transport industry. The first case examined the effects of vehicle travel speed and ambient temperature. The second case looked at the effects of bird size, loading density and ambient temperature. The last case studied the effects of side tarp insulation and ambient temperature. For the range of values examined, results from the simulations concluded that ambient temperature, bird sizes, loading density and side tarp insulation value were important factors to consider in the design of an actively ventilated poultry transport vehicle. The last chapter of this dissertation summarizes the main findings in this research project, discussed future work and presented final conclusions. Overall, this research project answered two key questions in the poultry transport research program. Firstly, the experimental work proved that the concept of active ventilation and heating is a promising option to improve the transport conditions for broiler chickens during cold ambient conditions. Secondly, the CFD work demonstrated that CFD modeling is a valuable tool for designing the next generation of actively ventilated poultry transport vehicle.

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Att använda fjärrvärme till lågenergihus kan vara olämpligt pga. höga kulvertförluster jämfört med kulvertförluster för traditionella hus. Detta beror på att det låga värmebehovet i lågenergihusen ger en hög returtemperatur i ledningarna. Ett steg för att öka värmebehovet och göra fjärrvärme mer attraktivt för lågenergihus är att börja värma upp vitvaror (tvätt-, diskmaskin och torktumlare) med fjärrvärme istället för att använda traditionella eluppvärma vitvaror. Vid installation av dessa vitvaror tillkommer en rördragning vars värmeförluster är önskvärda att hålla nere för att dels säkerställa önskad temperatur till vitvarorna men även för att hålla nere internvärmen i huset. I studien har olika rördimensioner och isoleringstjocklek analyserats för att se hur värmeförlusterna beror på strömningsparametrar. Av analysen ska de bästa alternativen för val av rör tas fram för en rördragning i luft respektive i betong. För att beräkna värmeförlusterna har simuleringsmodeller tagits fram i CFD-programmet (Computational fluid dynamics) Comsol Multiphysics. Studien är indelad i två delar. Första delen analyserar fem stycken standardrör med givna rördimensioner och isoleringstjocklek. Den andra delen av studien analyserar värmeförlusterna beroende på varierad isoleringstjocklek för de två minsta rördiametrarna hos standardrören. Resultatet i första studien visar att värmeförlusterna ökar med ökande rördiameter och att rörströmningen inte har någon betydande påverkan för värmeförlusterna. Andra studien visar att redan vid halva standardisoleringstjockleken kan värmeförlusterna minskas med 91 % jämfört med ett oisolerat rör. Simuleringarna visar att en rördragning i betong ger större värmeförluster än vid en rördragning i luft. Det beror på att betongen med dess ledningsförmåga förbättrar värmeavgivningen från röret mer än vad egenkonvektionen påverkar värmeförlusterna för en rördragning i luft. Vid val av vilket standardrör som skall användas med hänsyn till lägsta värmeförlust, är den minsta rördiametern bäst för en rördragning i luft. I betong däremot är värmeförlusterna lika stora för både det minsta röret och det mellersta standardröret. Skillnaden mellan de två rören är rördiametern samt att det är tjockare isolering på det mellersta röret.

The energy requirements of forage harvesters can be quite high and can sometimes determine the size of tractor needed on a farm. Therefore, improving the energy efficiency of the forage harvester could allow a farm to reduce costs by using a smaller tractor that is less expensive and more efficient. The objective of this research was to increase the throwing distance of a forage harvester by modeling the flow of forage in the spout and the air flow in the blower and spout. These models can then be used to compare the efficiencies of prototype designs. The air flow in the blower and spout was modeled using the commercial computational fluid dynamics software FLUENT. The simulation results of air velocities and flow patterns were compared to experimental values and it was found that both were of the same order of magnitude with the model predicting slightly higher air velocities than those measured. The flow of forage in the spout was modeled analytically by taking into account the friction between the forage and the spout surface and the aerodynamic resistance after the forage leaves the spout. From this model, two improved prototype spouts that should theoretically result in longer throwing distances were designed. However, field testing of the two prototypes did not reveal any significant improvements over the current design. It was also found that the model under-predicted the throwing distance of one prototype by 2 % and over estimated the other by 12 %.

The original design of a water-washed air cleaner, which developed by industry, only takes external design and assemblage into account, but the analysis of the overall performance wasn¡¦t studied. The air in the original water-washed air cleaner doesn¡¦t flow smoothly, which cause the inefficiency of the inlet and outlet flow, so there is a necessity to improve its performance. At beginning of this thesis study, the researcher designed the shape of the blades, and then analyzed the internal fluid field of the water-washed air cleaner. He also studied the impact of the efficiency of the aperture of diaphragm and the gap between blade and diaphragm. Finally, he obtained a series of result of simulation with simulating flow field produced by CFD to find out the best shape and amount of blades. The outlet flow performs better when £] is greater. However, when extreme values are between 50 degrees to 60 degrees, the smaller inclination of blade has better efficiency of the outlet flow. The amount of blades is not always positive to the efficiency. When the number of blades is more than 9, there is no significant increase of the outlet flow. The larger aperture of diaphragm has better efficiency, and decreases the gap between the blade and the diaphragm can increase outlet flow. Finally we obtained the result of optimization efficiency by Taguchi Method. After designing the best water washed air cleaner, the vibration is also simulated. The result of simulation showed that the nature frequency of overall structure is much higher than motor¡¦s, so that would not cause the resonant vibration.

There has been a continuous effort to unveil the physics of hypersonic flows both experimentally and numerically, in order to achieve an efficient hypersonic vehicle design. With the advent of the high speed computers, a lot of focus has been given on research pertaining to numerical approach to understand this physics. The features of such flows are quite different from those of subsonic, transonic and supersonic ones and thus normal CFD methodologies fail to capture the high speed flows efficiently. Such calculations are made even more challenging by the presence of nonequilibrium thermodynamic and chemical effects. Thus further research in the field of nonequilibrium thermodynamics is required for the accurate prediction of such high enthalpy flows. The objective of this thesis is to develop improved computational tools for hypersonic aerodynamics accounting for non-equilibrium effects. A survey of the fundamental theory and mathematical modeling pertaining to modeling high temperature flow physics is presented. The computational approaches and numerical methods pertaining to high speed flows are discussed. In the first part of this work, the fundamental theory and mathematical modeling pertaining to modeling high temperature flow physics is presented. Continuum based approach (Navier Stokes) and Boltzmann equation based approach (Gas Kinetic) are discussed. It is shown mathematically that unlike the most popular continuum based methods, Gas Kinetic method presented in this work satisfies the entropy condition. In the second part of this work, the computational approaches and numerical methods pertaining to high speed flows is discussed. In the continuum methods, the Steger Warming schemes and Roe’s scheme are discussed. The kinetic approach discussed is the Boltzmann equation with Bhatnagar Gross Krook (BGK) collision operator. In the third part, the results from new computational fluid dynamics code developed are presented. A range of validation and verification test cases are presented. A comparison of the two common reconstruction techniques: Green Gauss gradient method and MUSCL scheme are discussed. Two of the most common failings of continuum based methods: excessive numerical dissipation and carbuncle phenomenon techniques, are investigated. It is found that for the blunt body problem, Boltzmann BGK method is free of these failings.

An interface-preserving level set method is incorporated into the Reynolds-Averaged Navier-Stokes (RANS) numerical method to simulate the application of the green water phenomena around a platform and the breaking wave above the deck. In the present study, this method is used to evaluate the laminar in two dimension plane with fixed orthogonal grids. In this method, it is assumed that the free surface is modeled as immiscible two-phase flow (air and water). A level set function can present the individual fluids, and the interface between two-phase is represented by the zero level set. In addition, the level set evolution equation is coupled with the conservation equations for mass and momentum, which will be solved in the transformed plane. For different purposes, there are several block domains in the application grid. Chimera domain decomposition technique is employed to handle such embedding, overlapping, or matching grids. Several simple test cases were performed to demonstrate the feasibility of this method. The comparisons between the ENO scheme and the WENO scheme will be illustrated in the Zalesak's disk case and will further prove that the WENO scheme is superior to the ENO scheme. The propagation of continuous wave case will validate some properties of wave and determine the importance of some parameters in code. Moreover, the method will be applied in simulation of green water around a two dimensional platform. By configuring different deck heights, some distinct phenomena can be represented. Lastly, it is crucial to observe the green water phenomena around the platform deck by applying the velocity-extrapolation routine.

The study of the effect of different orbit paths and whirl ratios on the rotordynamic coefficients of a smooth eccentric annular seal, using Computational Fluid Dynamics (CFD) was performed. The flow was simulated for two different orbits - linear and circular for orbit speeds ranging from 0 to 1. This was done using the FLUENT CFD code with a time - dependent solver which allowed the use of dynamic meshing and User Defined Functions (UDFs). The effect of clearance was also studied by simulating the flow through an eccentric seal with one-tenth the clearance and comparing the results. It was seen that the flow field varies significantly with both the change in orbit and clearance and this in turn affects the forces and rotordynamic coefficients. The linear orbit showed major changes in terms of both the flow fields and the resulting forces. The velocities, pressure magnitudes and forces were much larger than the circular orbit. Another important finding was that the behavior of the flow for the smaller clearance is viscosity dominated compared to the inertia dominated flow seen for large clearances. The computation of rotordynamic coefficients for the circular orbits used Childs' theory and it was seen that for larger clearances the CFD predictions were not in agreement with the expected trends from this theory. The smaller clearance simulations, however, show force predictions from which the rotordynamic coefficients obtained match the theory.

The design of passive heat removal systems is one of the main concerns for the modular Very High Temperature Gas-Cooled Reactors (VHTR) vessel cavity. The Reactor Cavity Cooling System (RCCS) is an important heat removal system in case of accidents. The design and validation of the RCCS is necessary to demonstrate that VHTRs can survive to the postulated accidents. The commercial Computational Fluid Dynamics (CFD) STAR-CCM+/ V3.06.006 code was used for three-dimensional system modeling and analysis of the RCCS. Two models were developed to analyze heat exchange in the RCCS. Both models incorporate a 180 degree section resembling the VHTR RCCS bench table test facility performed at Texas A&M University. All the key features of the experimental facility were taken into account during the numerical simulations. Two cooling fluids (i.e., water and air) were considered to test the capability of maintaining the RCCS concrete walls temperature below design limits. Mesh convergence was achieved with an intensive parametric study of the two different cooling configurations and selected boundary conditions. To test the effect of turbulence modeling on the RCCS heat exchange, predictions using several different turbulence models and near-wall treatments were evaluated and compared. The models considered included the first-moment closure one equation Spalart-Allmaras model, the first-moment closure two-equation k-e and k-w models and the second-moment closure Reynolds Stress Transport (RST) model. For the near wall treatments, the low y+ and the all y+ wall treatments were considered. The two-layer model was also used to investigate the effect of near-wall treatment. The comparison of the experimental data with the simulations showed a satisfactory agreement for the temperature distribution inside the RCCS cavity medium and at the standpipes walls. The tested turbulence models demonstrated that the Realizable k-e model with two-layer all y+ wall treatment performs better than the other k-e models for such a complicated geometry and flow conditions. Results are in satisfactory agreement with the RST simulations and experimental data available. A scaling analysis was developed to address the distortion introduced by the experimental facility and CFD model in simulating the physics inside the RCCS system with respect to the real plant configuration. The scaling analysis demonstrated that both the experimental facility and CFD model give a satisfactory reproduction of the main flow characteristics inside the RCCS cavity region, with convection and radiation heat exchange phenomena being properly scaled from the real plant to the model analyzed.