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 13 of 13 for “"Skin Friction Drag"”.
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Skin friction drag reduction in turbulent flows using superhydrophobic surfaces
… potential approach for the passive reduction of skinfriction on the hull of ships, submarines and underwater projectiles. When submerged in water, these surfaces trap a layer of air (or 'plastron') within their texture, which allows the external fluid to partially slip over the boundary, …
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Experimental investigation into the reduction of supersonic skin-friction drag on a flat plate using transpiration and a cavity with mass addition
… evaluation of an operational facility for wall drag measurement and evaluation of the total drag of various wall configurations. The drag of three possible supersonic combustor wall configurations was measured to determine if reduction in skin friction and/or wave drag could be achieved through …
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High Fidelity Studies in Closed-Loop Control of Unsteady Aerodynamics
… boundary-layer to be lengthened, decreasing skin-friction drag on an airfoil. Analyses are conducted on a flat plate with an elliptical leading edge, later to be implemented in future studies with real airfoil geometry. The feedback control design employs strategically placed synthetic-jet …
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Aerodynamics study of the flowfield at a shelterbelt
… of the aerodynamic parameters, normal pressure drag and skin friction drag. The results obtained from this newly developed numerical scheme show satisfactory agreement with both field experiments and other numerical simulations. In addition, this procedure offers a generalized technique for …
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An Investigation of Dolphin-Groove Inspired Surface Patterning on Flow Control
… result from the micro-grooves found on dolphin skin (Tursiops truncates). A water tunnel was used to study a turbulent boundary layer over rigid 3D printed plastic models, and an adverse pressure gradient was created with a rotating cylinder to induce flow separation in the region of study. Each …
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Impact of Liquefied Natural Gas usage and payload size on Hybrid Wing Body aircraft fuel efficiency
… on 16% higher fuel specific energy, 17% lower skin friction drag through wall cooling on the wing bottom and 11-16% lower SFC through alternative cycles. Considerations were made for 1% insulation/fuel weight and 39% additional fuel volume but secondary systems and icing issues were not …
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Turbulent Boundary Layer over a Piezoelectrically Excited Traveling Wave Surface
… boundary layer with the aim of reducing skin friction drag. Spanwise traveling waves are a promising active drag reduction technique; however, the wave generation methods used in previous studies are bulky and could not be practically implemented. This research has developed an …
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Exploring plastron stability and fluid friction reduction on robust micro-textured non-wetting surfaces
… The utility of these surfaces in reducing skin friction in viscous laminar and turbulent flows is experimentally and theoretically investigated and is the main focus of this thesis. The development of a surface coating that reduces fluid drag can potentially lead to a number of practical …
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Turbulent drag reduction by anisotropic permeable substrates
… permeable substrates reduce turbulent skin-friction drag?' The first part of the thesis aims to extend the existing understanding on how complex surfaces of small texture size can reduce drag. We show that the effect of these surfaces can be reduced to an offset between the apparent, …
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Passive and active approaches to sustained turbulent hydrodynamic drag reduction using superhydrophobic surfaces
… the submerged body, allowing for a reduction in skin friction drag. I begin by identifying and fabricating several superhydrophobic surfaces, and testing their ability to reduce skin friction in turbulent flows using a bespoke Taylor-Couette apparatus. These superhydrophobic surfaces possess …
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Droplet levitation and underwater plastron restoration using aerophilic surface textures
… water droplets on the surface and lowering the skin friction drag experienced by the surface underwater. However, these aerophilic textures are prone to impregnation by water due to turbulent pressure fluctuations from external flows and dissolution of the trapped gas into the water. It is …
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Effects of Various Shaped Roughness Elements in Two-Dimensional High Reynolds Number Turbulent Boundary Layers
… element heights, k+, non-dimensionalized by the friction velocity (U_tau) of the approaching turbulent boundary layer, are 145, 145, 145, 145, 80, 98, and 98 respectively. Analysis of a three-dimensional fetch of the same Gaussian-shaped elements described previously was also undertaken. In order …
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Effects of surface roughness on the flow characteristics in a turbulent boundary layer
… data, a novel correlation that relates the skin friction to the ratio of the displacement and boundary layer thicknesses, which is valid for both smooth- and rough-wall flows, was proposed. In addition, it was also found that the application of a “mixed outer scale” caused the velocity …