Laminar–turbulent transition downstream of a backward-facing step (BFS) in a two-dimensional zero-pressure-gradient boundary layer is investigated computationally for step-height–to–local-displacement-thickness ratios of 0 < h / δ * < 1.6 . The nominally sharp BFS in a previous wind tunnel experiment is approximated via a smooth shape with a specified maximum slope. The laminar basic state solutions with the BFS are computed by solving the Navier–Stokes equations over a curvilinear grid. The linear amplification of Tollmien–Schlichting instabilities from the effects of basic state modification due to the BFS is quantified in terms of the logarithmic amplification ratio (or N factor) and computed with the harmonic linearized Navier–Stokes equations. The transition locations measured at nearly all test conditions with h / δ * < 1.3 correlate well with a computed N factor of N tr = 7.6 , demonstrating the first successful stability-based transition criterion related to step excrescences. An explanation for this successful correlation is that the net destabilization due to the BFS is the dominant contributor to the resulting shift in the transition onset location. The effect of any additional receptivity near the BFS does not play an important role in determining the movement of the transition front.


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    Title :

    Predicting Boundary-Layer Transition over Backward-Facing Steps via Linear Stability Analysis


    Contributors:

    Published in:

    AIAA Journal ; 58 , 9 ; 3728-3734


    Publication date :

    2020-07-24


    Size :

    7 pages




    Type of media :

    Article (Journal)


    Type of material :

    Electronic Resource


    Language :

    English




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