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PARAMETERS CONTROLLING ROUGHNESS EFFECTS IN A SEPARATING BOUNDARY LAYER

Carolyn D. Aubertine
Department of Mechanical Engineering, Stanford University Stanford, California 94305-3030, USA

John K. Eaton
Dept. of Mechanical Engineering Stanford University 488 Panama Mall Stanford, CA 94305 USA

Simon Song
Department of Mechanical Engineering Stanford University Stanford, CA 94305-3030, USA; Sandia National Laboratory Livermore, California 94551-9951, USA; Department of Mechanical Engineering, Hanyang University, Korea

Resumo

The effects of wall roughness were examined experimentally for two different rough-wall cases involving flow over a ramp with separation and reattachment. For these cases, the roughness Reynolds number was matched at two different momentum thickness Reynolds numbers. Both flow conditions were fully rough. The effect of increasing the wall roughness was to increase the friction velocity and increase the separation region size. The two rough-wall cases produced different size separation regions and different friction velocity values. In both cases, the outer layer turbulence was mainly affected by the change in the friction velocity.