Two-dimensional, direct numerical simulations are used to study the impact of active and natural (passive) suction at forward-facing steps on laminar–turbulent transition. Suction is applied through a gap in front of a step that is located in a flat-plate boundary-layer flow without streamwise pressure gradient. A steady base flow is used with a Mach number of 0.6. Subsequently, Tollmien–Schlichting waves are introduced by suction and blowing at the wall, and their growth over the surface imperfection is evaluated by N factors. The investigated step heights are in the range of one to two times the local displacement thickness of the smooth flat plate. Both sharp and rounded step corners are investigated. Cases with and without suction are compared with the smooth flat plate without suction based on Δ N factors according to the e N method. Thus, it is shown that suction is capable to compensate or even overcompensate the negative impact of different steps on laminar–turbulent transition. The work concludes with a configuration that allows natural (passive) suction in front of a forward-facing step. Here, a significant reduction of the N factor compared to the smooth flat plate without suction is possible. Further estimations indicate that a net drag reduction may be possible as well.


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    Title :

    Active and Natural Suction at Forward-Facing Steps for Delaying Laminar–Turbulent Transition


    Contributors:

    Published in:

    AIAA Journal ; 55 , 4 ; 1343-1354


    Publication date :

    2017-04-01




    Type of media :

    Article (Journal)


    Type of material :

    Electronic Resource


    Language :

    English






    Impact of Forward-facing Steps on Laminar-turbulent Transition in Transonic Flows Without Pressure Gradient

    Edelmann, C. / Rist, U. / American Institute of Aeronautics and Astronautics | British Library Conference Proceedings | 2013