This thesis presents the work undertaken to assess potential improvements in high performance bicycles. There are several wheel options available for elite riders to use in competition and this research has investigated the aerodynamic properties of different wheel type. The research has also developed CFD and FEA models of carbon fibre bicycle wheels to assist in the wheel improvements process. An accurate and repeatable experimental test rig was developed to measure the aerodynamic properties of bicycle wheels in the wind tunnel, namely translational drag, rotational drag and side force. Both disk wheels and spoked wheels were tested. It was found that disk wheels of different hub widths have different aerodynamic properties with the 53mm wide Zen disk wheel requiring the lowest total power of the wheels tested. There was little difference between the translational power requirements of the wheels but there was greater variation in the rotational power requirements. Compression spoked wheels of 3 and 5 spokes were found to require less power than wire spoked wheels. There was little difference between the total power requirements of the compression spoked wheels tested, with the differences at 50km/hr being less than the experimental uncertainty. The Zipp 808 wheel demonstrated considerably lower axial force than all other wheels at 10° yaw angle, confirming Zipp design intention to have optimum wheel performance between 0-20°. The Zen 3-spoke wheel showed the lowest axial drag and side force at yaw of the compression spoked wheels tested and had similar side force results to the Zipp 808. CFD models of the disk and 3-spoke wheel achieved good agreement with the experimental results in terms of translational drag. Rotational drag did not agree so well, most likely due to the turbulence model being designed for higher Reynolds number flows. A FE model of the disk wheel was validated with experimental testing. In order to simplify modelling, the FE model of the 3-spoke wheel did not include the hub, which led to a large discrepancy with experimental results for the particular loading scenario. The experimental rig and CFD models were used to develop aerodynamic improvements to the wheel and the FE models were used to identify the implication of geometric changes to the wheel structural integrity. These improvements are not reported in this thesis due to the results being commercially sensitive.

Active flow control is an area of heightened interest in the aerospace community. Previous research on flow control design processes heavily depended on trial and error and the designers knowledge and intuition. Such an approach cannot always meet the growing demands of higher design quality in less time. Successful application of computational fluid dynamics (CFD) to this kind of control problem critically depends on an efficient searching algorithm for design optimization. CFD in conjunction with Genetic Algorithms (GA) potentially offers an efficient and robust optimization method and is a promising solution for current flow control designs. Current research has combined different existing GA techniques and motivation from the two-jet GA-CFD system previously developed at the University of Kentucky propose the applications of a real coded Continuous Genetic Algorithm (CGA) to optimize a four-jet and a synthetic jet control system on a NACA0012 airfoil. The control system is an array of jets on a NACA0012 airfoil and the critical parameters considered for optimization are the angle, the amplitude, the location, and the frequency of the jets. The design parameters of a steady four-jet and an unsteady synthetic jet system are proposed and optimized. The proposed algorithm is built on top of CFD code (GHOST), guiding the movement of jets along the airfoils upper surface. The near optimum control values are determined within the control parameter range. The current study of different Genetic Algorithms on airfoil flow control has been demonstrated to be a successful optimization application.

A new parallel implicit adaptive mesh refinement (AMR) algorithm is developed for the prediction of unsteady behaviour of laminar flames. The scheme is applied to the solution of the system of partial-differential equations governing time-dependent, two- and three-dimensional, compressible laminar flows for reactive thermally perfect gaseous mixtures. A high-resolution finite-volume spatial discretization procedure is used to solve the conservation form of these equations on body-fitted multi-block hexahedral meshes. A local preconditioning technique is used to remove numerical stiffness and maintain solution accuracy for low-Mach-number, nearly incompressible flows. A flexible block-based octree data structure has been developed and is used to facilitate automatic solution-directed mesh adaptation according to physics-based refinement criteria. The data structure also enables an efficient and scalable parallel implementation via domain decomposition. The parallel implicit formulation makes use of a dual-time-stepping like approach with an implicit second-order backward discretization of the physical time, in which a Jacobian-free inexact Newton method with a preconditioned generalized minimal residual (GMRES) algorithm is used to solve the system of nonlinear algebraic equations arising from the temporal and spatial discretization procedures. An additive Schwarz global preconditioner is used in conjunction with block incomplete LU type local preconditioners for each sub-domain. The Schwarz preconditioning and block-based data structure readily allow efficient and scalable parallel implementations of the implicit AMR approach on distributed-memory multi-processor architectures. The scheme was applied to solutions of steady and unsteady laminar diffusion and premixed methane-air combustion and was found to accurately predict key flame characteristics. For a premixed flame under terrestrial gravity, the scheme accurately predicted the frequency of the natural buoyancy induced oscillations. The performance of the proposed parallel implicit algorithm was assessed by comparisons to more conventional solution procedures and was found to significantly reduce the computational time required to achieve a solution in all cases investigated.

The main aim of this thesis is to compare actual power production from an existing wind farm with power production prediction by WindSim, which is a CFD tool based on the nonlinear flow model. The wind farm that is being worked on is located in Northern Sweden and has high orographic complexity with forested hilly terrain. There is 1 year record of met-mast wind measurements and nearly 2 years record of production data.Firstly roughness and height contours data are put as an input in order to simulate and generate wind fields over the complex terrain. In addition forest model is used to get more detailed roughness height. After generating wind fields existing turbine locations and 1-year wind speed measurement are imported.The results show that how accurate are the CFD calculations to solve turbulence in a complex terrain. Comparison between actual production data with energy production results by simulations is the main approach of this thesis work to validate the simulations.The results indicate that both WAsP and WindSim have overestimated energy production and wind speed as well. However particularly with WindSim forest module CFD calculations have more accurate results than without forest module and WAsP estimations.

Photocatalysis is a green technology that has been widely used in wastewater treatment. In this work, mass transfer processes in corrugated photocatalytic reactors were characterized both experimentally and through computer simulations. For the experimental work, various drum rotational speeds, reactor liquid volumes and number of corrugations were studied to elucidate their effects on mass transfer phenomena. The mass transfer rate was found to increase with increasing rotational speed. Liquid volumes in the reactor significantly affect the mass transfer rate when 20% of the surface area of the drum was immersed. A higher mass transfer rate was found using the drum with 28 corrugations, which had the lowest mass transfer coefficient when compared to the drums with 13 and 16 corrugations. In the computer simulations, velocity and concentration fields within the corrugated reactors were modelled to explore the characteristics of mass transfer processes. The mass transfer coefficients predicted by the simulations were lower than those measured experimentally due to mass transfer limitations occurring between the corrugation volume and bulk solution in the simulations. Based on mass transfer characteristics, it was determined that the drum with 28 corrugations was the most efficient photocatalytic reactor, and had the lowest mass transfer coefficient among those studied.

In SCUBA diving, the propulsive efficiency of a diver regulates, in part, his autonomy. An inefficient method of propulsion will increase the power output required and, therefore, the intake of oxygen and increase fatigue. Since the development of the SCUBA apparatus, fins have evolved based on the designer's intuition and knowledge of hydrodynamics. Some experimental work has been performed, but it is usually limited to studying the diver as whole and does not focus on the fin design. In this dissertation, a state-of-the-art fluid-structure interaction framework is developed and then used to study fin propulsion. This framework couples the structural dynamics of the fin with the fluid dynamics surrounding it using a modular framework. This way, mature state-of-the-art solvers can be used in each domain (structural and fluid). The flow field is solved using a computational fluid dynamics solver which resolves the Navier-Stokes equations. Coupled with these equations are a variety of turbulence models which can be used to resolve the turbulence in the flow. The CFD method is validated using a two-dimensional circular cylinder and a pitching and heaving airfoil, both immersed in a turbulent flow field. A commercial structural dynamics solver, is used to resolve the structural dynamics. The coupling of the two solvers is also described in detail. The basic design of a fin (a simple flat plate) is studied and modified in order to test the effect that altering key structural parameters has on the thrust, power and efficiency of the fin. The end result is a set of design recommendations which can be used to enhance the performance of a SCUBA fin. These recommendations are based on both quantitative and qualitative analysis of the performance characteristics of the fin.

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In this work a cooling system connected to a reactor pressure vessel has been studied using the CFD method for the purpose of investigating the strengths and shortcomings of using CFD as a tool in similar fluid flow problems within nuclear power plants. The cooling system is used to transport water of 288K (15°C) into a nuclear reactor vessel filled with water of about 555K (282°C) during certain operating scenarios. After the system has been used, the warm water inside the vessel will be carried into the cooling system by buoyancy forces. It was of interest to investigate how quickly the warm water moves into the cooling system and how the temperature field of the water changes over time. Using the open source CFD code OpenFOAM 2.3.x and the LES turbulence modelling method, a certain operating scenario of the cooling system was simulated. A simplified computational domain was created to represent the geometries of the downcomer region within the reactor pressure vessel and the pipe structure of the cooling system. Boundary conditions and other domain properties were chosen and motivated to represent the real scenario as good as possible. For the geometry, four computational grids of different sizes and design were generated. Three of these were generated using the ANSA pre-processing tool, and they all have the same general structure only with different cell sizes. The fourth grid was made by the OpenFOAM application snappyHexMesh, which automatically creates the volume mesh with little user input. It was found that for the case at hand, the different computational grids produced roughly the same results despite the number of cells ranging from 0,14M to 3,2M. A major difference between the simulations was the maximum size of the time steps which ranged from 0,3ms for the finest ANSA mesh to 2ms for the snappy mesh, a difference which has a large impact on the total time consumption of the simulations. Furthermore, a comparison of the CFD results was made with those of a simpler 1D thermal hydraulic code, Relap5. The difference in time consumption between the two analyses were of course large and it was found that although the CFD analysis provided more detailed information about the flow field, the cheaper 1D analysis managed to capture the important phenomena for this particular case. However, it cannot be guaranteed that the 1D analysis is sufficient for all similar flow scenarios as it may not always be able to sufficiently capture phenomena such as thermal shocks and sharp temperature gradients in the fluid. Regardless of whether the CFD method or a simpler analysis is used, conservativeness in the flow simulation results needs to be ensured. If the simplifications introduced in the computational models cannot be proved to always give conservative results, the final simulation results need to be modified to ensure conservativeness although no such modifications were made in this work.