Spelling suggestions: "subject:" boundary"" "subject:" foundary""
381 |
Numerical Investigations of Transition in Hypersonic Flows over Circular ConesHusmeier, Frank January 2008 (has links)
This thesis focuses on secondary instability mechanisms of high-speed boundary layers over cones with a circular cross section. Hypersonic transition investigations at Mach 8 are performed using Direct Numerical Simulations (DNS). At wind-tunnel conditions, these simulations allow for comparison with experimental measurements to verify fundamental stability characteristics.To better understand geometrical influences, flat-plate and cylindrical geometries are studied using after-shock conditions of the conical investigations. This allows for a direct comparison with the results of the sharp cone to evaluate the influence of the spanwise curvature and the cone opening angle. The ratio of the boundary-layer thickness to the spanwise radius is used to determine the importance of spanwise curvature effects. When advancing in the downstream direction the radius increaseslinearly while the boundary-layer thickness stays almost constant. Hence, spanwise curvature effects are strongest close to the nose and decrease in downstream direction. Their influences on the secondary instability mechanisms provide some rudimentary guidance in the design of future high-speed air vehicles.In experiments, blunting of the nose tip of the circular cone results in an increase in critical Reynolds number (c.f. Stetson et al. (1984)). However, once a certain threshold of the nose radius is exceeded, the critical Reynolds number decreases even to lower values than for the sharp cone. So far, conclusive explanations for this behavior could not be derived based on the available experimental data. Therefore, here DNS is used to study the effect of nose bluntness on secondary instability mechanisms in order to shed light on the underlying flow physics. To this end, three different nose tip radii are considered-the sharp cone, a small nose radius and a large nose radius. A small nose radius moves the transition on-set downstream, while for a large nose radius the so-called transition reversal is observed. Experimentalists hold influences of the entropy layer responsible but detailed numerical studies may lead to alternateconclusions.
|
382 |
Flow in a porous medium driven by differential heatingPunpocha, Mahosut January 2000 (has links)
No description available.
|
383 |
On the influence of lateral boundaries in nonlinear convectionHo, Diep January 2000 (has links)
No description available.
|
384 |
On the behaviour of nanoscale fluid samples far from equilibriumHouston, Peter Henry Robert January 2000 (has links)
No description available.
|
385 |
Numerical failure modeling of composite structuresPadhi, Gouri S. January 2000 (has links)
No description available.
|
386 |
Analytical and numerical methods for the acoustic scattering from finite structuresJames, David Alun January 1999 (has links)
No description available.
|
387 |
Direct and inverse scattering by rough surfacesRoss, Christopher Roger January 1996 (has links)
No description available.
|
388 |
The scattering of elastic waves by rough surfacesArens, Tilo January 2000 (has links)
No description available.
|
389 |
Weathering history of a late Cretaceous palaeosol, Northeast IrelandMc Cann, Oonagh January 1999 (has links)
No description available.
|
390 |
Modelling the sources of marine CCN and their contribution to global albedoYoon, Young Jun January 2001 (has links)
No description available.
|
Page generated in 0.0577 seconds