LINK BETWEEN FLOW SEPARATION AND TRANSITION ONSET

The relationship between the location of boundary-layer separation and transition onset in compressible subsonic now is studied. The now sep aration considered in this study is caused by a localized adverse pres sure gradient that results from a single roughness element (a hump) on an otherwise smooth flat plate. The mean flow is computed with the in teracting boundary-layer (IBL) approach, and a quasiparallel stability analysis of the resulting profiles is performed. The N-factor criteri on with N = 9 is used to correlate transition. The effects of unit Rey nolds number, hump location, hump length, and freestream Mach number o n the relationship between separation and transition location are eval uated. Our results support the customary assumption that the separatio n location can be taken as the transition onset location in a certain parameter space; however, this assumption is not valid in other ranges of the parameter space, particularly at low unit Reynolds numbers, fo r short humps, and at relatively high freestream Mach numbers.