Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 57 for “"Vortical structures"”.
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Vortical structures in turbomachinery tip clearance flows
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1991.
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Three-dimensional vortical structures in the wake of a flexible flapping foil
… gain a qualitative view of the three-dimensional vortical structures of a flexible flapping foil at Reynolds number 164. Flexible foils were fabricated, coated with fluorescent dye, and towed with heave and pitch in a large glass tank. The foil cross section is a NACA 0030 foil shape, and the foil …
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The Near Wake of a European Starling
… imply the presence of (secondary) streamwise vortical structures, in addition to the wing tip vortices. The lack of downwash during the upstroke and the suggestion of secondary streamwise vortical structures constitute a deviation from a wake model which has been developed and supported by …
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Laboratory Analysis of Vortex Dynamics For Shallow Tidal Inlets
… is the propagation of large two dimensional vortical structures. At the mouth of an inlet, tidal flow forces the formation of two dimensional vortical structures whose lateral extent is much greater than the water depth. After the starting jet vortex dipole detaches from the inlet, secondary …
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Experimental study of turbulence past thin tabs
… the tab geometry on the strength of the induced vortical structures at the low Re. The turbulent flow regime at high Re promotes high shear stress and TKE production right past the tabs, where the rectangular tab induces greater mixing. The spanwise vortices from the rectangular tab have an …
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Lagrangian simulation of transverse jets with a distribution-based diffusion scheme
… is dominated by large-scale and small-scale vortical structures, whose inter-related dynamics is a challenging subject in modern fluid mechanics. This study seeks a mechanistic understanding of the vortical structures of the transverse jet and their evolution. A set of massively parallel …
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Hemodynamic Flow Characterization of St. Jude Medical Bileaflet Mechanical and Bioprosthetic Heart Valve Prostheses in a Left Ventricular Model via Digital Particle Image Velocimetry
… are presented. The presence and location of vortical structures were deduced as well as the level of coherence of these structures. The presence of three distinct flow patterns were identified, by the location of vortical structures and level of coherence, for the three configurations …
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Numerical Simulation of Vortex Generating Jets in Zero and Adverse Pressure Gradients
… A shell wall structure, created by smaller vortical structures surrounding the developing vortices, was also observed. A pulsed jet in a zero pressure gradient was then initialized from a no-control case. A qualitative comparison between averaged experimental and instantaneous numerical …
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Numerical investigations of vortex dynamics: bursting, twist waves, and sensitivity analysis
Vortical structures are ubiquitous in real-world fluid flows, from the vortices generated by swimming fish to the wakes of aircraft and propellers. They form the backbone of high Reynolds number turbulent flows. Their dynamics are governed by non-linear processes, leading to a range of vortical …
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An impulse framework for hydrodynamic force analysis : fish propulsion, water entry of spheres, and marine propellers
… (2) the vortex impulse required to create the vortical structures in the wake of the body. Fish generate propulsive forces by creating and manipulating large-scale vortical structures using their body and tail. High-speed particle image velocimetry experiments show that a fish generates two …
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Direct numerical simulation of large bubbles in a free shear layer
… flow field in conjunction with the large scale vortical structures of the liquid. The role of large bubbles in modifying finite Reynolds number shear flow structures was investigated, specifically for bubbles whose diameter approaches the scale of the largest liquid eddies. Both two- and …
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Experiments with impulsive motion of a foil to generate large lift and thrust forces
… with a custom wing to elucidate the wake and vortical structures produced by these strokes.
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Flow Visualization Study of Wake-Stabilized Diffusion Flames in a Crossflow: Effects of Crossflow Turbulence
… crosswind turbulence on the mechanisms and flow structures affecting emissions from non-premixed wake stabilized flames from elevated stacks are investigated. In the current work, two conditions of upstream crossflow are tested to investigate the effects of turbulence on the flame, including the …
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Investigation of the Effects of an Upstream Cavity on the Secondary Flow in Transonic Turbine Blade Passages with Endwall Contouring
… it aims to improve the understanding of vortical structures near the endwall with respect to the presence of an upstream cavity that approximates the gap present in actual engines between the rotor and stator of an HP turbine. Further, it aims to assess the viability of using …
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Aeroacoustics of perforated drag plates for quiet transport aircraft
… responsible for the noise radiated by unsteady vortical structures can be changed to small length scales driving jet noise at frequencies which are perceived unannoying by the human ear. The aeroacoustic characteristics of laboratory-scale perforated spoilers were measured in an acoustic chamber …
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Computations of Flow Structures and Heat Transfer in a Dimpled Channel at Low to Moderate Reynolds Number
… at Re = 2000. The presence of large scale vortical structures ejected from the dimple cavity dominate all aspects of the flow and heat transfer, not only on the dimpled surface but also on the smooth wall. In all cases the thermal efficiency using dimples was found to be significantly …
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The hemisphere-cylinder at an angle of attack
… to provide information on the development of vortical structures on the surface of the model. Comparisons were made of the results obtained using these two instruments. The flowfield in the wake of the hemispherecylinder was also examined at an angle of attack α = 30°. A small bead was …
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The attenuation of flow-induced tonal noise using plasma actuators
… surveys around the electrode elements reveal vortical structures produced by the plasma actuators. It is shown that these structures convect downstream with the mean flow and produce disturbances similar to that of vortex generators. This affects the convection of spanwise discrete vortices in …
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The Interaction of a Transient Forward Axial Disturbance Flow With a Rotor
… <p>Additionally, a detailed analysis of wake structures revealed substantial alterations, characterized by intensified turbulence and increased vortex interactions. The research identified a marked increase in broadband noise attributable to these turbulent phenomena and the subsequent …
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Vorticity structure and evolution in a transverse jet with new algorithms for scalable particle simulation
… they exemplify flows dominated by coherent structures that cascade into smaller scales, a source of many current challenges in fluid dynamics. This study seeks a fundamental, mechanistic understanding of the relationship between the dispersion of jet fluid and the underlying vortical …
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