The theoretically validated Fage’s transition criterion for predicting transition in flow over a single roughness element is used to show that in the widely used roughness Reynolds number (Rek) transition criterion, the critical value of Rek depends strongly on the length of the roughness element. At roughness length where the criterion is valid, the variation of the roughness height with free-stream Reynolds number is quantified.

Issue Section:
Technical Briefs
Topics:
Reynolds number, Surface roughness, Flow (Dynamics)
1.
Fage, A., 1943, “The Smallest Size of Spanwise Surface Corrugation Which Affect Boundary Layer Transition on an Airfoil,” British Aeronautical Research Council, Report and Memoranda No. 2120.
2.
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3.
Hansman, R. J., 1993, “Microphysical Factors Which Influence Ice Accretion,” Proceedings of the First Bombardier International Workshop on Aircraft Icing and Boundary-Layer Stability and Transition, I. Paraschivoiu, ed., ISBN 2-553-00422-2, pp. 86–103.
4.
Masad
J. A.
, and
Iyer
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,
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Transition Prediction and Control in Subsonic Flow Over a Hump
,”
Phys. Fluids
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6
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5.
Masad, J. A., and Malik, M. R., 1994, “On the Link Between Flow Separation and Transition Onset,” AIAA Paper No. 94-2370.
6.
Morkovin, M. V., 1993, “Bypass-Transition Research: Issues and Philosophy,” Instabilities and Turbulence in Engineering Flows, Ashpis, Gatski and Hirsh, eds., Kluwer Academic Publishers, pp. 3–30.
7.
Schlichting, H., 1979, Boundary-Layer Theory, 7th ed., McGraw Hill, New York, pp. 536–537.
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