Direct numerical simulation is used to investigate the transition induced by three-dimensional isolated roughness elements in a supersonic boundary layer at a freestream Mach number of 3.5. Simulations are performed for two different configurations: one is a square planform roughness element, and the other is a diamond planform roughness element. The mean flow calculations show that the roughness element induces counter-rotating streamwise vortices downstream of the roughness element. These vortices persist for a long distance downstream, lift the low-momentum fluid from the near-wall region, and place it near the outer part of the boundary layer. This forms highly inflectional boundary-layer profiles. These observations agree with recent experimental observations. The receptivity calculations show that the amplitudes of the mass-flux fluctuations near the neutral point for the diamond-shaped roughness element are the same as the amplitude of the acoustic disturbances. They are three times smaller for the square-shaped roughness element.


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    Title :

    Roughness-Induced Transition in a Supersonic Boundary Layer


    Contributors:

    Published in:

    AIAA journal ; 2322-2337


    Publication date :

    2016




    Type of media :

    Article (Journal)


    Type of material :

    Print


    Language :

    English



    Classification :

    BKL:    50.93 / 55.50 Luftfahrzeugtechnik / 50.93 Weltraumforschung / 55.60 Raumfahrttechnik / 55.50 / 55.60
    Local classification TIB:    770/7040




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