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Sedimentation is a phenomenon well characterized in nature by the fallout of solids and liquids from the atmosphere, and the settling out of sediment in the oceans and inland waterways. It has been used on an industrial scale in many applications notably in the separation of solids and liquids in gravity settling tanks and in centrifugal devices for the rapid dewatering of slurries. In the laboratory it is adapted to techniques for characterizing fine particles. Observation of the phenomenon may be complicated by electrostatic or magnetic fields, thermal gradients, eddy currents, complicated rheological properties of the sedimenting fluid or irregular particle shape and density, and particle concentration.

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Digital microscopic holographic particle image velocimetry (DµHPIV) is a technique which records scattered coherent light and uses it to measure displacement of particles in a fluid flow. The work in this thesis begins with the construction of a digital holographic microscope and explores the different possible methods of recording and holographic reconstruction, finding an off-axis forward-scatter geometry to be most suitable for the task. A comparison follows of methods to measure displacement in a sparsely seeded environment by performing a simple experiment. It finds that complex amplitude correlation performs significantly better than both intensity correlation and nearest neighbour analysis; the two other possible methods of displacement tracking. Later, an experiment is performed to investigate the behaviour of a microfluidic blood separator. The separator is intended to remove blood plasma from whole blood without other contaminants such as red blood cells and without the need for expensive laboratory equipment. In this chapter a new technique, higher order correlation, is introduced which can be used to strengthen the peaks in correlations of three or more particle images in a flow, and a potential flow CFD model of the separator is built from scratch to predict whether the separator will work, and against which the results can be compared. Finally, there is an experiment carried out which for the first time allows aberration free imaging within objects with irregular, highly curved surfaces; in this case optical fibres and inkjet droplets, by numerically reconstructing the droplet surface.

This PhD dissertation investigates the noise radiation produced by a rotor inside a duct, which is convected by a swirling-translating mean flow. The study is based on an extension of Gennaretti's and Morino's boundary element method to the frequency domain for scattering problems in conjunction with a spinning rotor source model in the presence of a swirling-translating flow. Firstly, two different source models of the rotor are analyzed in absence of mean flow. The parametric study of the two dipole components distributed over a ring or a disc shows that the source radius is a crucial parameter. The scattered pressure directivity patterns of the ring and disc source models are in perfect agreement when a particular ratio between the two model radii is adopted. Therefore, the present analysis justifies the preference for the ring source model due to its simplicity. The proposed formulation is validated by means of exact solutions and used to investigate the effects of the translating flow Mach number and swirling flow angular velocity on noise radiation both in the far and in the near field. The scattered sound is highly affected by the convecting mean flow. The modal content of the scattered field increases when increasing the translating flow Mach number, while a swirling flow leads to a reduction of the mode propagation, if co-rotating with respect to the azimuthal order of the spinning source, or an increase of the modal content, if counter-rotating with respect to the source. This is clearly confirmed by the scattered pressure patterns and levels both in the far and in the near field for all the source frequencies. In general, the mean translating flow moves the main lobes of the directivity patterns downstream, whereas in some cases the mean swirling flow appears to neglect this effect and the downstream lobe is completely shifted. However, the investigation on the in-duct propagation shows that the main effect of the convecting mean flow is to change the modal duct characteristics, more than the pattern itself. This results in turn in the strong modification of the patterns noted in the far field.

Ducts can be found in ventilation systems, cooling ducts and blade passages of turbines, centrifugal pumps and many other engineering installations. The properties of the flow in ducts can significantly affect the performance and efficiency of these installation areas. The majority of the flows in ducts and engineering applications are turbulent. The work presented in this thesis focuses on the analysis of turbulent flows inside square sectioned ducts and ducts with bends. The accuracy of three different high resolution high order schemes in the context of Implicit Large Eddy Simulation (ILES) is analysed. The influence of a low Mach limiting technique, Low Mach Number Treatment (LMNT) is also studied. The schemes employed are Monotonic Upwind Scheme for Scalar Conservation Laws (MUSCL) with a 2nd order Monotonized Central (MC) and 5th order limiter, and a 9th order Weighted Essential Non-Oscillatory (WENO) limiter. The first case studied is a duct of square cross section . In the absence of experimental data for the duct case, the data from a plain channel flow is used to shed light on the results. The flow analysis points out the generation of secondary motions created by the existence of surrounding walls. All schemes employed lead to a similarly developed turbulent flow that is used to provide the turbulent boundary profile for the following case. LMNT proves to significantly assist MUSCL 2nd and 5th, that use it, in providing a turbulent profile similar to that of WENO 9th that did not employ the technique but is inherently less dissipative. The second case under study is that of a square sectioned duct with a 90o bend. The simulation output is in good agreement both qualitatively and quantitatively with the experimental data available in the literature. The generation of secondary flows inside the bend is observed without flow separation. Although the turbulent flow entering the domain is almost the same for all cases, differences between the schemes are noticed especially after the middle of the bend. LMNT leads to an overprediction of turbulence after that area for both schemes employing it while WENO 9th without LMNT provides the most accurate results compared to those provided by the experiment. The results demonstrate applicability of ILES to strongly confined flows with secondary motions and shed light on cognitive properties of a wide range of state of the art schemes.

The interest in hypersonic flow phenomena has peaked in recent years where number of experimental and computational work has been carried out. The Computational Fluid Dynamics (CFD) is fast becoming an invaluable tool to investigate compressible hypersonic flow phenomena that are extremely complex in nature. Mathematical models employed to describe complex physical phenomena that take place at hypersonic speeds inherit varying degrees of accuracy and reliability. Therefore, further studies, numerical and experimental, are needed to clarify and improve these models. Numerical computation is one of the tasks that are vital in the overall hypersonic flow research effort. This work investigated the applicability and performance of higher resolution methods to simulate high enthalpy real gas flows. Furthermore, gas-surface interaction and ablation effects are also investigated. In order to achieve the set task, it is imperative that the numerical code (CNS3D) used is equipped with necessary numerical and physical models to tackle flow behaviour typically unique to hypersonic flow. Therefore, the implementation of mathematical models that describe the real gas phenomena, such as vibrational effects, chemical dissociation, diffusion, and high enthalpy effects, has been carried out. The test cases, the HB-2 flare and the double-cone have been considered for the purposes of verification and validation. The experimental data for heat transfer and pressure are compared with numerical predictions to assess the behaviour of modified CNS3D overall and each numerical scheme with regards to reconstruction methods. The overall agreement between the predicted results for both cases and the experimental data is satisfactory. The stagnation point values of pressure and heat flux for HB-2 flare testcase at varying Mach numbers from 5 to 17.8 has been established; these values are expected aid future validation efforts. It was also found that very high-order schemes, such as WENO 5th and 9th -order methods, may provide slightly better results for free stream Mach numbers less than 10; however, there are no obvious benefits over second-order methods for Mach numbers greater than 10. Furthermore, it has been substantiated that increasing order of accuracy compared to increments in the grid resolution is much more effective way of gaining accuracy in the case of real gas flows.