Includes bibliographical references (p. 207-212).

Thesis (Ph.D)--Aerospace Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Menon, Suresh; Committee Member: Ruffin, Stephen; Committee Member: Sankar, Lakshmi; Committee Member: Stoesser, Thorsten; Committee Member: Yeung, Pui-Kuen. Part of the SMARTech Electronic Thesis and Dissertation Collection.

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The effect of waveform shape and extension of negative flowrate are studied at two Reynolds numbers (Re = 80, Re = 200) on stented channels by looking at the kinematics and dynamics of the flow. The waveforms are reconstructed by Fourier decomposition of a waveform corresponding to left anterior descending (LAD) of coronary artery. The stents are modeled by an immersed boundary method. Two stent geometries are created which are the idealizations of two clinical ones. The first geometry is an idealization of XIENCE V stent which is called Lambda stent and the second one is the idealization of Endeavor stent and is called X stent. The former has larger inter-strut spacing and smaller thickness than the latter one. The use of immersed boundary method for creating the stents is validated, and the spatial resolution requirements are determined. The shape of the waveform is changed by systematically filtering out the higher modes of Fourier decomposition and the negative flowrate extension is reduced by shifting the waveform to the positive flowrate. The presence of the stent causes vortical structures to be created between stent struts. These vortices are migrating to the centre of the channel and disappear. It is observed that the confined geometric feature of X stent and its larger thickness, leads to larger areas of flow recirculation which causes smaller wall-shear-stress parameters with respect to Lambda stent and more deviation of the flow from a healthy vessel. The importance of the convective terms of the Navier-Stokes equations was studied at the two Reynolds numbers for both stents. It is observed that at high Reynolds number (Re = 200), the convective terms play significant role throughout the waveform cycle while at low Reynolds number (Re = 80), the effect of convective terms become negligible during negative flowrate. Moreover the convective terms become more significant for flow in a channel with Lambda stent than X stent due to the specific shape and size of the stents. The kinematics of the flow corresponds to the study of vortex timing. It was found that this timing is mainly affected by the waveform and Reynolds number rather than the stent geometry. The time at which vortex creation occurs is coincident with the time at which wall shear stress changes its sign in an unstented channel. Therefore the analytical solution of unsteady channel flow can be used as a tool for analysing the kinematics of the flow, / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2012-06-07 17:41:52.501

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A series of experiments has been conducted for comparison with the results of a computer code called CHYMES. It is intended to calculate the coarse mixing of molten metal with water by solving the equations of the Separated Flow Model. These are derived by volume averaging and the terms that relate them to the particular case of participate flow are discussed. An experimental apparatus that is compatible with CHYMES and coarse mixing has been constructed which projects a jet of ball bearings into a thin tank of water. Experiments over a wide range of conditions were conducted at room temperature. Owing to practical difficulties only one, poorly controlled experiment with hot ball bearings was performed. Under nearly all sets of conditions an arrow-shaped plume was obtained. The speed of penetration of the plume varied little with changes in experimental conditions. The width of the plume was most strongly influenced by the widths of the tank and the jet. The individual paths of some particles were followed; it appeared that their motion was mostly dependent on their position in the plume. A model of the plume is proposed, based upon its front being impermeable to water in the vertical direction. Much of the detail of the experimental plumes was not present in the computational results and they responded differently to changes in conditions. It is proposed that this is a result of the different forms of the two sets of plumes. To rectify this an experimental plume was volume averaged. A method to determine a suitable averaging volume size is described. The process results in a plume similar to the computational ones. The length scales required for volume averaging to be successful are discussed and the possibility that this method is inappropriate for describing coarse mixing is admitted.

The subject of the thesis is concerned with the study of the turbulent spreading and the gravity spreading processes in surface jets and surface plumes influenced by the cross-flow. A total of five different discharge and cross-flow configurations were under investigation. They are, namely, (i) submerged jets in unconfined cross-flow, (ii) surface jets in deep and shallow cross-flows, (iii) surface plumes in deep cross-flow, (iv) full-depth jets in cross-flow and (v) full-depth plumes in cross-flow, reported in Chapters IV, V, VI, VII and VIII respectively. / The effect of the gravity stratification, the effect of the free water surface and the confined effect of the channel bottom on the spreading of the turbulent flows have been determined from control experiments. The experimental data have been correlated in a unified manner, using suitable scales and dimensionless parameters. They are also related to a general integral formulation, established for this type of problems. / The results of an extensive series of previous experimental investigations, of related problems of jets and plumes in cross-flow have been reanalysed and they are integrated into the various parts of the thesis to complement and confirm the present investigation. / On the whole, the thesis has succeeded in providing a general description of the turbulent spreading and the gravity spreading processes in flows of different discharge and cross-flow configurations.

Bibliography: leaves 228-262. / xxvi, 262, [xxvii] leaves : ill. (chiefly col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This thesis reports on a fundamental investigation of a precessing jet flow which is analogous to that which emanates from the fluidic nozzle. A 'mechanical nozzle' is used to generate a well-defined PJ flow. / Thesis (Ph.D.)--University of Adelaide, Dept. of Mechanical Engineering, 1997?

Thesis (MSc)--University of Stellenbosch, 2007. / Bibliography. Also available via the Internet.