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Published February 1968 | public
Journal Article

Far wake behind cylinders at hypersonic speeds: II. Stability

Behrens, W.

Abstract

At Reynolds numbers below 10^4 the inner viscous wake behind cylinders at Mach 6 is entirely laminar. At these low Reynolds numbers the outer wake caused by the bow shock becomes transitional thousands of diameters downstream. Flowfield measurements (Part I) indicated strong deviations from the behavior of laminar steady flow from a certain point on, suggesting a division into linear and nonlinear wake instability regions. Fluctuation measurements confirm this supposition at four Reynolds numbers. Wake instabilities were investigated experimentally up to a distance of 12,000 dimeters behind the cylinder in a Reynolds number range of 200 to 4,000. Additional measurements were performed in the regime where both inner and outer wake instabilities occur. In the linear region close correspondence with linear inviscid stability theory was found. The nonlinear instability region is a long stretched-out region in comparison with the wake at low speeds behind a flat plate. A further increase of the fundamentally instability component and a sudden growth of the first harmonic is observed. A tentative picture is given of the onset of nonlinearity and/or transition in the inner and outer wakes behind blunt bodies at hypersonic speeds.

Additional Information

© 1968 AIAA. Presented as Part II of Paper 67-32 at the AIAA 5th Aerospace Sciences Meeting, New York, January 23-26, 1967. Submitted April 17, 1967; revision received August 9, 1967. This work was carried out under the sponsorship and with the financial support of the U.S. Army Research Office and the Advanced Research Projects Agency under Contract DA-31-124-ARO(D)-33. This research is part of Project Defender sponsored by the Advanced Research Projects Agency. The author wishes to express his sincere thanks and deep appreciation to L. Lees for his guidance and support throughout this research and to T. Kubota, who was always available to give invaluable advice.

Additional details

Created:
August 19, 2023
Modified:
October 26, 2023