It is shown in this thesis that fluid dynamic forces on unsteadily moving bluff bodies depend on the history of motion as much as on the velocity and acceleration of motion. An empirical relationship between the motion of the body and the resulting force is obtained by analysing the effect of the history of motion on the fluid dynamic force at any instant. The fluid dynamic force, velocity and acceleration are obtained as functions of time, by oscillating test models in water while they are being towed at constant speed. The test models used are: 1. a two-dimensional circular cylinder, 2. a rectangular block with square frontal area and fineness ratio of 3:1, 3. a cruciform parachute canopy with arm ratio of 4:1, and 4. a ring-slot parachute canopy. The functions by which the history of flow affects the future forces, are evaluated by using the Convolution Integral. The results show that the effects due to history of both velocity and acceleration are by no means negligible, that is the velocity and the acceleration at a specific time prior to any instant is so domineering that the fluid dynamic force can approximately be expressed as being delayed by this period of time. This 'time-delay', or time lag (as opposed to phase-lag) in the part of the measured force is found to be independent of the frequency of excitation. In the light of this evidence, a prediction model is suggested for estimating unsteady fluid forces. The data required for the application of this prediction model are obtained experimentally. Chapter One of this thesis gives a brief explanation of the historical background of unsteady fluid dynamics. The effects of acceleration on the fluid dynamic force, in both ideal and real fluids, are discussed in Chapter Two. Explained in Chapter Three are the techniques used for building the force prediction model, and data acquisition. The experimental procedure is explained in Chapter Four. Chapter Five gives the empirical form of the prediction model, and some data that are used in association with this model.

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Please read the abstract in the dissertation. / Dissertation (MSc)--University of Pretoria, 1965. / gm2014 / Electrical, Electronic and Computer Engineering / Unrestricted

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In the subsurface faults can act as both barriers and conduits for fluids or gases such as CO2, hydrocarbons, or water. It is often thought that faults in porous rocks such as sandstone are barriers to fluid flow. In this study we show that this is not always the case. In sandstones like the Cedar Mesa Sandstone it is very important to understand the relationships between this history of fault slip and fluid flow. Better understanding of how fluids migrate through faults and the damaged areas surrounding these faults has strong significance to the oil and gas industry. In this study we examine a group of faults and their surrounding damage zones near Hite, Utah. We analyze three of these small-scale faults in more detail. In doing so we give insights into how these faults and their damage zones can effect fluid migration as well as the porosity and permeability in the Cedar Mesa Sandstone. Whole rock geochemistry, X-ray diffraction mineralogy, permeability data, petrography, ultraviolet photography, and outcrop observations were used to gain insights into cross-cutting relationships, past fluid compositions, and fault characteristics. From the data that was collected from these faults we have begun to describe a series of structural and fluid flow events. This series allows us to say that small-scale faults and fractures are features by which fluids can migrate preferentially. In this series of events we isolate two separate phases of movement. The first phase of movement being has a component of shear in which the edges of the fractures are not moving directly apart. This event is accompanied by a fluid flow event the emplaced iron oxide in the fractures and the surrounding formation. The second event is a phase when the faults become reactivated by a stress that created open mode fractures. This second is accompanied by a fluid flow event that has high calcium content and emplaces calcite in the fractures. Throughout this study we give evidence to support this series of movement and fluid events.

Prostaglandins (PGs) are important signalling factors for bone mechanotransduction. The inhibition of cyclooxygenase, responsible for the synthesis of PGs, with non-steroidal anti-inflammatory drugs (NSAIDs) has been shown to influence bone formation induced by mechanical stimulation. The purpose of this study was to examine the timing effects of NSAID administration on: 1) bone formation induced by multiple mechanical loading events in a rat model and 2) the PGE2 response of MLO-Y4 osteocyte like cells stimulated by fluid shear stress. The rat forelimb compression model was used to induce bone formation in male and female rats using a 1-month loading protocol (12 loading sessions). The right forelimbs were loaded and the left forelimbs served as non-loaded controls. NSAIDs were administered orally either before or after loading. Fluorochrome labels were administered to the rats to determine mineral apposition rate (MAR). The NSAIDs examined (indomethacin, NS-398 and ibuprofen) did not significantly affect periosteal MAR, administered either before or after loading, suggesting NSAIDs do not affect bone adaptation to multiple mechanical loading events. To examine in vitro effects of NSAIDs on PGE2 production, an orbital shaker was used to apply fluid shear stress to MLO-Y4 cells seeded in 6-well culture plates. Indomethacin was added to the culture media either before or after loading and media PGE2 concentrations were determined at various time points by enzyme immunoassay. Fluid shear stress increased PGE2 production of MLO-Y4 cells and indomethacin administration inhibited that response when administered both before and after fluid flow. However, PGE2 production was influenced by the media changes that occurred in the in vitro experiments, making it difficult to differentiate between indomethacin effects and media change effects. The in vitro experiments revealed the difficulties of modeling the timing effects of NSAID administration on MLO-Y4 PGE2 production in response to fluid flow. / Thesis / Doctor of Philosophy (PhD) / Bone is a dynamic tissue that can adapt to mechanical loading. Prostaglandins (PGs) are important signalling factors produced by osteocytes, the bone mechanosensing cells, that help to activate various cells and cell processes leading to changes in bone structure. Blocking PG signalling with non-steroidal anti-inflammatory drugs (NSAIDs) has been shown to influence bone formation induced by mechanical stimulation in animals and humans. The purpose of this study was to examine the timing effects of NSAID administration on: 1) bone formation induced by multiple mechanical loading events in rats and 2) the PG production of osteocyte like cells in response to fluid flow stimulation. The results of this study suggest that NSAIDs, administered either before or after loading, do not affect bone responses to multiple mechanical loading events. Further investigation is needed to determine the translatability of these findings to NSAID use around the time of exercise in humans.

Cavitation inside an automotive torque converter running at various pump speeds was simulated by using the Computational Fluid Dynamics (CFD) commercial package ANSYS-CFX 10.0/11.0. The numerical solution obtained for the case with no cavitation was used as an initial condition for the case of flow with cavitation to accelerate convergence. The converter was initially modeled using several grid sizes to evaluate the effect of grid density on the numerical solution and to select the optimum grid size for subsequent simulations. Comparison of CFD to actual test results demonstrates that the cavitation model built in the commercial code, which was developed by Zwart et. al. (2004) based on the simplified Rayleigh-Plesset equation of bubble dynamics, does not capture the full effect of cavitation inside the converter. Modifications to this model have been investigated in this study. The effect of the variation of the automotive transmission oil vapor pressure due to the rise in temperature during normal operating conditions was also investigated and found not to cause any significant change to the area of vapor formation, and hence did not have a significant effect on the converter performance. Values of the empirical coefficients of the cavitation model had to be modified in order for the model to capture the full effect of cavitation on the performance of the converter operating at high pump speeds. Results showed a much larger area of vapor over the converter stator and traces of vapor appeared inside the pump, and turbine blades. With these modifications, the model produced results in better agreement with the available experimental data. Moreover, simulations have been carried out in both steady and transient states using various turbulence models available in CFX10.0/11.0 in order to evaluate the effect of the choice of turbulence models on cavitation prediction. / Thesis / Master of Applied Science (MASc)

The accuracy of plenoptic and tomographic particle image velocimetry (PIV) experimental methods is measured by simulating three-dimensional flows and measuring the errors in the estimated versus true velocity fields. Parametric studies investigate the accuracy of these methods by simulating a range of camera numbers, camera angles, calibration errors, and particle densities. The plenoptic simulations combine lightfield imaging techniques with standard tomographic techniques and are shown to produce higher fidelity measurements than either technique alone. The tomographic PIV simulations are centered around testing software developed for processing large quantities of data that were produced during an experimental investigation of the flow field about a 3D printed model of the flying snake Chrysopelea paradisi. A description of this tomographic PIV experiment is given along with basic results and recommendations for future investigation. / Doctor of Philosophy / Two different experimental measurement techniques that can be used to measure three-dimensional fluid flow fields are discussed. The first measurement technique that is investigated in simulations uses cameras with arrays of lenses to simultaneously capture images of a flow field from multiple different angles. A method of combining the data from multiple cameras is discussed and shown to yield more accurate estimates of the three-dimensional flow fields than from a single camera alone. An additional measurement technique that uses a group of standard cameras to measure three-dimensional flow fields is also discussed with respect to software that was developed for processing a large volume dataset. This software was developed for processing data collected during an experimental investigation of the flow field about a 3D printed model of the flying snake Chrysopelea paradisi. A description of this experiment is given along with basic results and recommendations for future investigation.

We consider the application of least-squares variational principles and the finite element method to the numerical solution of boundary value problems arising in the fields of solidand fluidmechanics.For manyof these problems least-squares principles offer many theoretical and computational advantages in the implementation of the corresponding finite element model that are not present in the traditional weak form Galerkin finite element model.Most notably, the use of least-squares principles leads to a variational unconstrained minimization problem where stability conditions such as inf-sup conditions (typically arising in mixed methods using weak form Galerkin finite element formulations) never arise. In addition, the least-squares based finite elementmodelalways yields a discrete system ofequations witha symmetric positive definite coeffcientmatrix.These attributes, amongst manyothers highlightedand detailed in this work, allow the developmentofrobust andeffcient finite elementmodels for problems of practical importance. The research documented herein encompasses least-squares based formulations for incompressible and compressible viscous fluid flow, the bending of thin and thick plates, and for the analysis of shear-deformable shell structures.