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 106 for “"Drag Reduction"”.
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Aerodynamics drag reduction of commercial trucks
… Gull Wing truck, with a view to reducing the drag of the truck. To investigate the flow over the truck, a 1:20 scale double trailer truck model was designed and constructed from chipboard for wind tunnel experiments. The overall size of the model is 1100 mm long, 130 mm wide and 215 mm high. A …
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Drag Reduction by Polymeric Additive Solutions
… known to effectively reduce turbulent friction drag by up to 80 %. Conducted in the Hydrodynamics Laboratory in Virginia Tech, this research presents a comprehensive analysis into drag reducing effects through experimental, theoretical, and computational analyses. A major focus of this research …
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Turbulent drag reduction by anisotropic permeable substrates
… 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, virtual smooth …
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Micro-textured surfaces for omniphobicity and drag-reduction
When a liquid droplet contacts a surface possessing the appropriate combination of surface texture and solid surface energy, the liquid may not penetrate into the surface texture. Instead, the droplet sits partially on air, forming a solid-liquid-air composite interface. Entrapped air pockets of …
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Drag reduction by polymer solutions in riblet pipes
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1995.
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Aerodynamic drag reduction of a racing motorcycle through vortex generation
The aerodynamic drag of a racing-class motorcycle can be accomplished through either an overall redesign of the surfaces or through some type of flow control mechanism. Due to limitations on the size of the exterior shape the flow control techniques are more practical. Small metal vanes, known as …
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Experimental implementation of Lorentz force actuators for hydrodynamic drag reduction
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002.
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Geometry mediated drag reduction using riblets and wrinkled surface textures
… such as skin friction. Inspired by the drag reducing ability of these natural structures, especially the ribbed features on shark denticles, passive drag reduction strategies such as micro-fabricated riblet surfaces have been developed and studied. Microgroove textures on the surface of …
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Implementation of travelling waves on lifting surface for drag reduction
… of such airfoils is to attain a large lift-to-drag ratio, namely increasing the lift force while reducing the drag force. At moderate angles of attack, boundary layer separation begins near the trailing edge, and moves up to the leading edge as the angle increases. Such a phenomenon raises the …
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Skin friction drag reduction in turbulent flows using superhydrophobic surfaces
… interest as a 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 …
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Active Drag Reduction of Ground Vehicles Using Air-Jet Wheel Deflectors
… k-e, k-w, DES, and LES all trended towards a drag coefficient which was 20% lower than the experimental value. In all numerical cases, the lift coefficient was found to be at least 60% greater than the experimental value, but was consistent with numerical studies by other authors. The standard …
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Numerical Prediction of Drag Reduction and Interfacial Shapes Over Superhydrophobic Surfaces
… methodologies are developed to study the drag-reducing effects of superhydrophobicity for realistic surfaces. A multiphase Navier--Stokes volume-of-fluid based approach is developed to investigate the effect of interface curvature, and turbulence on drag reduction in the presence of …
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Drag reduction using riblet film applied to airfoils for wind turbines
… presents results of a study to investigate the drag reduction properties of riblet film on airfoils specifically designed for wind turbine applications. The S809 and DU 96-W-180 airfoils were tested with four different symmetrical V-shaped riblet sizes (44, 62, 100 and 150 μm) at three Reynolds …
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Turbulent flow enhancement by polyelectrolyte additives : mechanistic implications for drag reduction
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1992.
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Hydrophobic coatings for film boiling based drag reduction on a torpedo model
… porous, hydrophobic surfaces exhibit a dramatic reduction in critical heat flux (CHF), the amount of heat over a surface area required to initiate film boiling. Film boiling is characterized by the presence of a vapor layer which remains as long as the surface temperature stays above the …
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Analysis of Viscous Drag Reduction and Thermal Transport Effects for Microengineered Ultrahydrophobic Surfaces
… pressure is not too high. The net result is a reduction in the surface contact area between channel walls and the flowing liquid. For micro-ribs and cavities that are aligned normal to the channel axis (principal flow direction), these micropatterns form a repeating, periodic structure. This …
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Polymers and plastrons : active and passive drag reduction in wall-bounded turbulent flows
… the flow of liquids through pipelines, to the drag-inducing boundary layer around ships and submarines. The effective mitigation of this frictional drag is therefore of great practical interest, and offers substantial economic and environmental benefits. This thesis focuses on two complementary …
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Active and passive separation control for drag reduction of a maneuvering hull form
… cross-flow separation to reduce the drag of hull forms in maneuvers. A new strategy is proposed for designing flow control mechanisms for the three dimensional flow past maneuvering hull forms based on the unsteady cross-flow analogy. The unsteady cross-flow analogy relates the steady …
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Composite compliant coatings for drag reduction utilizing low modulus high damping silicone rubber
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1985.
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Passive and active approaches to sustained turbulent hydrodynamic drag reduction using superhydrophobic surfaces
… the water and 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 …
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