In this work, numerical simulations of flow separation control are performed. The sep-aration control technique studied is called 'synthetic jet actuation'. The developed code employs a cell centered finite volume scheme which handles viscous, steady and unsteady compressible turbulent flows. The pulsating zero mass jet flow is simulated by imposing a harmonically varying transpiration boundary condition on the airfoil's surface. Turbulence is modeled with the algebraic model of Baldwin and Lomax. The application of synthetic jet actuators is based in their ability to energize the boundary layer, thereby providing signifcant increase in the lift coefficient. This has been corroborated experimentally and it is corroborated numerically in this research. The performed numerical simulation investigates the flow over a NACA0015 air-foil. For this flow Re = 9??105 and the reduced frequency and momentum coefficient are F+ = 1:1 and C?? = 0:04 respectively. The oscillatory injection takes place at 12.27% chord from the leading edge. A maximum increase in the mean lift coefficient of 93% is predicted by the code. A discrepancy of approximately 10% is observed with corresponding experimental data from the literature. The general trend is, how-ever, well captured. The discrepancy is attributed to the modeling of the injection boundary condition and to the turbulence model.A sensitivity analysis of the lift coefficient to different values of the oscillation parameters is performed. It is concluded that tangential injection, F + ?? O(1) and the utilized grid resolution around the site of injection are optimal. Streamline fields ob-tained for different angles of injection are analyzed. Flow separation and attachment as functions of the injection angle and of the velocity of injection can be observed. It is finally concluded that a reliable numerical tool has been developed which can be utilized as a support tool in the optimization of the synthetic jet operation and in the modeling of its operation.

Reconfiguration refers to the ability of a flexible structure to change its shape, allowing it to reduce its area perpendicular to the flow, to reduce drag. Decreasing the flexural rigidity of human-made structures can lead to improved designs that operate at higher propulsive efficiencies. The work presented in this thesis examines the physics surrounding a flexible plate under prescribed oscillatory heaving motions. White light movies were recorded at constant frequency and varying proximity to the free surface to investigate the change in reconfiguration as the plate approaches the free surface. Results, analyzed in terms of deformed plate shape, deflection, and plate tip kinematics, found that free surface effects increase the deflection of the plate as the plate approaches the free surface. Expanding on the initial experiments, a variety of frequencies were tested. The results show that each heaving frequency has a different critical height to the free surface in which deep water behavior is distinguished from shallow water behavior. At the critical depth, the plate deflection becomes asymmetric due to free surface effects. The second stage of experiments focused on measuring the fluid loading and fluid flow surrounding the flexible plate. The fluid loading, or drag force, acting on the plate was estimated by using a strain gauge load cell. Results of these experiments found that the drag force is equivalent on plates with lower heaving frequencies when compared to the highest heaving frequency tested due to increased reconfiguration at the higher frequency. The fluid moved from the keel to the edge of the plate as seen in the particle image velocimetry experiments. Higher heaving frequencies created faster fluid flow off the plate and stronger tip vortices being shed from the plate. When the flexible plate operated at large distances from the free surface, the fluid dynamics showed the same behavior for the upstroke and downstroke of the plate. Whereas, when the plate operated close to the free surface, a vortex only forms on the upstroke, leading to asymmetric loading and deformations. / Master of Science / The ability for a structure to bend under loading and return to its original shape after the load is removed presents a desirable characteristic for structural design. The flexibility of the structure can lead to significant weight loss in contrast to rigid structures. In nature, almost all structures are able to bend when faced with fluid forces which decreases the loading the structure has to handle. Decreasing the stiffness of human-made structures can lead to improved designs that operate at higher propulsive efficiencies. The work presented here examines the physics surrounding a flexible plate under prescribed oscillatory heaving motions, which are motions that are purely vertical. White light movies were recorded at constant frequency and varying proximity to the free surface to investigate the change in plate shape as the plate approaches the free surface. Results, analyzed in terms of deformed plate shape, deflection, and plate tip kinematics, found that free surface effects increase the deflection of the plate as the plate approaches the free surface. Expanding on the initial experiments, a variety of frequencies were tested. The results show that each heaving frequency has a different critical height to the free surface in which deep water behavior is distinguished from shallow water behavior. At the critical depth, the plate deflection becomes asymmetric due to free surface effects. The second stage of experiments focused on describing the fluid loading and fluid flow surrounding the flexible plate. The fluid loading, or drag force, acting on the plate was estimated by using a strain gauge load cell. Results of these experiments found that the drag force is equivalent on plates with lower heaving frequencies when compared to the highest heaving frequency tested due to increased reconfiguration at the higher frequency. The fluid moved from the center of the plate to the edge of the plate as seen in the particle image velocimetry experiments, which track the movement of particles in the fluid. Higher heaving frequencies created faster fluid flow off the plate. When the flexible plate operated at large distances from the free surface, the fluid flow showed the same behavior for the upstroke and downstroke of the plate. Whereas, when the plate operates close to the free surface, the fluid flow behaves differently leading to asymmetric loading and deformations.

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Many applications in engineering practice can be described by thehyperbolic partial differential equations (PDEs). Numerical modeling of this typeof equations often involves large gradients or shocks, which makes it achallenging task for conventional numerical methods to accurately simulate suchsystems. Thus developing accurate and efficient shock capturing numericalschemes becomes important for the study of hyperbolic equations.In this dissertation, a detailed study of the numerical methods for linearand nonlinear unsteady hyperbolic equations was carried out. A new finitedifference shock capturing scheme of finite volume style was developed. Thisscheme is based on the high order Pad?? type compact central finite differencemethod with the weighted essentially non-oscillatory (WENO) reconstruction toeliminate non-physical oscillations near the discontinuities while maintain stablesolution in the smooth areas. The unconditionally stable semi-implicit Crank-Nicolson (CN) scheme is used for time integration.The theoretical development was conducted based on one-dimensionalhomogeneous scalar equation and system equations. Discussions were alsoextended to include source terms and to deal with problems of higher dimension.For the treatment of source terms, Strang splitting was used. For multidimensionalequations, the ?? -form Douglas-Gunn alternating direction implicit(ADI) method was employed. To compare the performance of the scheme withENO type interpolation, the current numerical framework was also applied usingENO reconstruction.The numerical schemes were tested on 1-D and 2-D benchmark problems,as well as published experimental results. The simulated results show thecapability of the proposed scheme to resolve discontinuities while maintainingaccuracy in smooth regions. Comparisons with the experimental results validatethe method for dam break problems. It is concluded that the proposed scheme isa useful tool for solving hyperbolic equations in general, and from engineeringapplication perspective it provides a new way of modeling open channel flows.

Oscillatory integral operators have been of interest to both mathematicians and physicists ever since the emergence of the work Theorie Analytique de la Chaleur of Joseph Fourier in 1822, in which his chief concern was to give a mathematical account of the diffusion of heat. For example, oscillatory integrals naturally arise when one studies the behaviour at infinity of the Fourier transform of a Borel measure that is supported on a certain hypersurface. One reduces the study of such a problem to that of having to obtain estimates on oscillatory integrals. However, sub-level set operators have only come to the fore at the end of the 20th Century, where it has been discovered that the decay rates of the oscillatory integral I(lambda) above may be obtainable once the measure of the associated sub-level sets are known. This discovery has been fully developed in a paper of A. Carbery, M. Christ and J.Wright. A principal goal of this thesis is to explore certain uniformity issues arising in the study of sub-level set estimates.

Caramel is a mixture of sugars, milk proteins, fat and water cooked at high temperatures to initiate Maillard reactions. We study caramels as ‘active emulsion-filled protein gels’, in which fat droplets are chemically-bonded to a background gel matrix of cross-linked proteins in a concentrated aqueous sugar solution. A ‘caramel region’ in composition space is delimited by the varying the four ingredients; sugar, milk protein, fat and water. The boundaries of the composition space define various modes of ‘failure’. Boundaries are determined for transitions to toffee and emulsification failure leaking out of the caramel, and protocol dependent failures, scum formation during the cooking step and subsequent boil over or the formation of a ‘creme Chantilly. Oscillatory rheology within the caramel region reveals that we can superpose the mechanical spectra of all caramels into a single pair of G'(ω),G''(ω) master curves using time-composition superposition (tCS) over 12 decades of frequency, so that all caramels are instances of an underlying ‘universal material’. The master curve is an example of a very lightly cross-linked amorphous polymer, a weak rubber. Utilising the cross-over point of G'(ω) and G''(ω) as a common point to compare caramel master curves the viscous and elastic dependency of caramel is determined and linked to the caramels ingredients. Viscosity is dependent on the aqueous sugar content and the elastic dependency on protein content. This insight constrains the molecular mechanisms for structure formation, and implies that measuring a couple of parameters suffices to predict the rheology of caramels over 12 orders of magnitude in frequency.

Osteocytes are believed to be the mechanosensory cells that detect and respond to mechanical loading. Physiological loading by oscillatory fluid flow (OFF) activates osteocytes to increase intracellular calcium concentration and release prostaglandin E2 (PGE2). Osteocytes are also sensitive to chemical stimulations such as serotonin, which can also increase PGE2 release. However, it is unclear whether mechanical stimulation can influence osteocyte sensitivity towards serotonin. In this thesis, MLO-Y4 osteocyte-like cells were subjected to serotonin with or without precondition by OFF, the responses of intracellular calcium and PGE2 release were measured. Serotonin increased intracellular calcium and PGE2 release in osteocytes. The effects were significantly reduced by OFF precondition, suggesting mechanical precondition by OFF can reduce osteocyte sensitivity towards serotonin. In terms of mechanisms, OFF- and serotonin-induced calcium responses depended on intra- and extracellular calcium stores. ATP was found to partially mediate OFF modulation of serotonin-induced PGE2 release but not calcium.

Osteocytes are believed to be the mechanosensory cells that detect and respond to mechanical loading. Physiological loading by oscillatory fluid flow (OFF) activates osteocytes to increase intracellular calcium concentration and release prostaglandin E2 (PGE2). Osteocytes are also sensitive to chemical stimulations such as serotonin, which can also increase PGE2 release. However, it is unclear whether mechanical stimulation can influence osteocyte sensitivity towards serotonin. In this thesis, MLO-Y4 osteocyte-like cells were subjected to serotonin with or without precondition by OFF, the responses of intracellular calcium and PGE2 release were measured. Serotonin increased intracellular calcium and PGE2 release in osteocytes. The effects were significantly reduced by OFF precondition, suggesting mechanical precondition by OFF can reduce osteocyte sensitivity towards serotonin. In terms of mechanisms, OFF- and serotonin-induced calcium responses depended on intra- and extracellular calcium stores. ATP was found to partially mediate OFF modulation of serotonin-induced PGE2 release but not calcium.

This study aims to search the optimal system structure for a specific type of oscillatory wave-energy acquisition system, which owns the highest efficiency in acquiring the energy from sea wave. The system is mainly consisted of a float, a generator and several oscillators that are connected to the float or to each other by the elastic springs. In addition, all the components are capsulated in the float. For the purpose of comparison, when aided with an active control, the acquiring efficiency of the system with a near optimal structure is analyzed. Under the assumption of random sea wave, three steps are adopted to investigate the optimal system structure. First, the mathematical model of the capsulated float that can acquire the maxima power from sea wave is derived by the spectrum analysis. They offer the messages that what the dynamic properties of an optimal structure should be in order to acquire the maxima power. Second, the dynamic properties of the general system are analyzed. It is to examine the effect of increasing system¡¦s degrees of freedom in offering the flexibility of varying system dynamics to match the desired ones. The limitation of increasing the degrees of freedom is especially examined. Then, the maxima attainable powers for the systems with different degrees of freedom are simulated by the genetic algorithm. It is to support the inference made from the analysis about the effect of increasing the system¡¦s degrees of freedom. Finally, a preliminary examination of the effect of active control in power acquisition is done. The study indicates that an oscillatory system structure with two degrees of freedom is a near optimal structure for energy acquisition. An increase of system¡¦s degree of freedom shows little effect in improving system¡¦s dynamic characteristics in the main frequency range of sea wave. The proposed active control scheme is shown to be effective in improving the system¡¦s dynamic characteristics to enhance the energy acquisition from sea wave. However, the extra-energy consumed in the control action makes the increase of net energy acquisition negligible.

The purpose of this thesis is to develop a novel design of the oscillatory type of wave-energy acquisition system. It is aimed to increase the efficiency of wave-power acquisition from random sea. The main feature of the new system structure is its flexibility to adjust the system dynamics to satisfy two optimal criteria. The effects of various system parameters on the system dynamics and acquired power were analyzed. To find the set of system parameters to acquire the highest power, an optimization searching method was adopted. Finally, a regression model was established to help the user to calculate the optimal system parameters under various application conditions. The study first indicated that to acquire high power from sea wave the dynamic characteristics of the system should satisfy two criteria. However, the study also revealed that the dynamic properties of a traditional acquisition system are difficult to fulfill the two criteria in a wide frequency band. Accordingly, a new system structure was proposed. It is composed of a traditional acquisition system and a vibrating platform. The platform is linked to the acquisition system through a spring. Because of the coupling effect, the dynamic characteristics of the acquisition system are altered. The effects of varying different system parameters on the locations of pole or zero of the transfer function of acquisition system were examined. It was shown that with a proper choice of system parameters, the frequency bandwidth satisfying or close to the two criteria may be increased. The study indicated that acquired power of the proposed system is higher than the traditional one by 34%.