Electronic Resource
[S.l.]
:
American Institute of Physics (AIP)
Physics of Fluids
29 (1986), S. 3199-3213
ISSN:
1089-7666
Source:
AIP Digital Archive
Topics:
Physics
Notes:
Distributed roughness with nominal height k in a boundary layer with displacement thickness δ* is known to lead to early non-Tollmien–Schlichting–Schubauer (TS) transition when k/δ* exceeds unity in nonaccelerated flows. But could commonly occurring milder random roughness enhance the regular phase-conditioned TS mechanisms and also lead to early transition? The new affirmative answer rests on extensive hot-wire explorations and smoke-wire visualization of flow over smooth and rough walls. The effects appear to be threefold. First, the low-inertia fluid in the valleys between the elements evidently respond more readily to free-stream disturbances. Second, once the TS fluctuations commence, they grow faster. Whether this is caused by continued input from free-stream disturbances along the path or to an increased destabilization of the system or both remains unclear. No inflected mean boundary-layer profiles were registered in careful measurements. Third, there is evidence of roughness-induced three-dimensionalization of the wave fronts which leads to earlier secondary subharmonic instabilities and, hence, to turbulence.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.865838
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