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 77 for “"boundary layer thickness"”.
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Solution of the laminar boundary layer of a semi-infinite flat plate given an impulsive change in velocity and temperature
The laminar boundary layer over a semi-infinite flat plate which is impulsively set in motion in an incompressible fluid and which has a simultaneous step change in surface temperature was studied. An approximate method was derived which can be used to determine the thermal boundary layer thickness …
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Local flowfield about large distributed roughness elements in a laminar boundary layer
… elements placed in a flat plate laminar boundary layer was studied. Flowfield measurements were taken upstream, over, and downstream of an isolated hemispherical roughness element and distributed hemispherical roughness elements. The height of the roughness elements was large compared to …
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Computational analysis of magnetohydrodynamics boundary layer flow of nanofluid over a stretching sheet in the presence of heat generation or absorption and chemical reaction
… is ratio of buoyancy to viscous forces in the boundary layer it causes an increase in the buoyancy forces relative to the viscous forces which influence the velocity in the boundary layer region. An increase in the heat source/sink parameter (S) results in the increase in velocity and …
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The physiological importance of small leaf sizes in the mediterranean type ecosystem vegetation of the Cape floristic region
… and heat loss are partially dependent on boundary layer conductance, which is determined by leaf shape and size, surface modifications and wind speed. We expected fine-leaved species with higher boundary layer conductance to transpire faster than broad-leaved species at low temperatures …
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The effects of pressure waves on turbulent oblique shock wave boundary layer interactions in rectangular channels
Oblique Shock Wave--Boundary-Layer interactions (oblique SBLIs) occur in many practical applications, such as in mixed compression supersonic jet intakes and transonic compressor cascades and can have significant detrimental effects on the downstream boundary layer, resulting in flow distortion, …
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Stratified and stirred : monsoon freshwater in the Bay of Bengal
… a critical role in setting the ocean's surface boundary layer thickness and associated density stratification. Submesoscale instabilities contribute to lateral stirring and tracer dispersal. These dynamics are investigated in the Bay of Bengal, motivated by the upper ocean's potentially coupled …
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Measurements of the structure of urban-type boundary layers
… spanwise variation discovered within the boundary layer developing over the cube surface. It was found that mean velocity variation in the span at a height of 50% of the boundary layer thickness could exceed ±5%. Further testing was conducted at locations far enough downstream to minimise …
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Aerodynamics of Runback Ice Accretions
… were similar in height to the clean-model local boundary-layer thickness acted to stabilize the recovering boundary layer, delaying stall past the stalling angle-of-attack of the clean case.
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Effect of large distributed roughness near an airfoil leading edge on boundary layer development and transition
… has been performed to determine the effect on boundary-layer development and transition. Boundary-layer measurements were carried out on a two-dimensional NACA 0012 airfoil with a 21"" chord. The distributed roughness used was in the form of densely packed large hemispherical elements applied …
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Optimization of a Vortex Generator Configuration for a 1/4-Scale Piper Cherokee Wing
… vortex generator height relative to the local boundary layer thickness. The vortex generator angle of incidence relative to the freestream was varied from 10 to 30 degrees in increments of 5 degrees. Other variables included were spanwise row density, chordwise row location as well as number of …
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Experimental study of supersonic slot injection into a supersonic stream
… of 1.27 cm, which was also approximately the boundary layer thickness in the primary stream, and a thin splitter plate with a thickness of 0.052 cm. Computer controlled measurement systems were used at four streamwise stations, (x/a) = 0.25, 4, 10, 20, to determine cone static pressure, pitot …
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Modeling of Kinetically Limited Growth Rate for Solution-Synthesized Germanium Nanocrystals
… of 10-5 to 10-4 cm2/sec, while the mass transfer boundary layer thickness is estimated to be on the order of a few nanometers, similar to the nanocrystal size. These two realistic conditions strongly suggest that the common assumption on diffusion limitation may not be warranted and that surface …
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The effects of periodic wake disturbances on flat-plate turbulent boundary layers
… unsteady periodic wakes that interact with the boundary layer and free stream flows about downstream blades. This study modelled these flow conditions, with circular cylinders periodically traversing in front of a turbulent flat plate boundary layer inside a low speed wind tunnel. These cylinder …
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Boundary Layer Characteristics on a Tiltrotor Blade Model
Boundary layer characteristics at the trailing edge of a tiltrotor blade model were measured using a flattened pitot probe and a single hot wire. The blade was mounted in Virginia Tech Stability Wind tunnel stationary on a turntable on the wind tunnel's upper wall with the tip pointing down. The …
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Application of a Helmholtz resonator excited by grazing flow for manipulation of a turbulent boundary layer.
… is typically sufficiently high such that the boundary layer is turbulent. Flow instabilities within the turbulent boundary layer can result in an excessive drag penalty which is considered to be the main parameter affecting the aerodynamic efficiency in numerous applications including aircraft …
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The Space-time Structure of an Axisymmetric Turbulent Boundary Layer Ingested by a Rotor
A low-speed, axisymmetric turbulent boundary layer under a strong adverse pressure gradient is experimentally studied for its relevance to marine applications, urban air-transportation and turbulence ingestion noise. The combined effect of lateral curvature and streamwise pressure gradient are …
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An experimental investigation of unsteady separation shock wave motion in a plume-induced, separated flowfield
… separation shock wave motion in plume-induced, boundary layer separated (PIBLS) flowfields has been conducted. The PIBLS flowfields were created in a blowdown-type wind tunnel designed specifically to produce PIBLS in a planar, two-stream, supersonic flow. In this unique wind tunnel, separation …
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The penetration and mixing of a sonic hydrogen jet injected normal to Mach 4 airstream
… flush mounted in a flat plate with a turbulent boundary-layer thickness of 2.70 injector exit diameters at the injector station. The investigation was conducted for values of the dynamic pressure ratio ranging from 0.5 to 1.5. At five downstream stations between 7 and 200 injector diameters the …
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The Noise of a Boundary Layer Flowing Over Discrete Roughness Elements
… recording for the flow of a turbulent wall jet boundary layer over cubes, hemispheres, and gravel, with element heights in the range of 14.3 - 55.2% of the boundary layer thickness. The sound radiated from the various layouts showed that the elements acted as independent sources when separated …
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Numerical simulations of vortices near free and solid surfaces
… the two-dimensional interaction between a boundary layer and a convecting vortex. The size and height above the wall of the vortex are the same order of magnitude as the boundary layer thickness. A strong primary vortex creates a secondary vortex which causes the rebound of the primary, a …
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