Oscillations in cylinder wakes at Mach 4
The wake behind a circular cylinder in Mach 4 flow is examined experimentally in the Reynolds number range 2×10^4 to 5×10^5. Periodic oscillations of the sliplines in the wake are observed. The Strouhal number of the oscillations based on the diameter of the cylinder is found to increase monotonically from 0.30 to 0.50 with increasing Reynolds number. If the Strouhal number is formed using the length of the sliplines, however, it has a constant value of approximately 0.48 for all Reynolds numbers studied. This scaling indicates that the oscillations in supersonic flow are likely driven by acoustic signals propagating back and forth through the subsonic region between the separation points on the cylinder and the neck where the sliplines converge, unlike in subsonic flow where oscillations are caused by vortices shed from the cylinder surface.
© 2015 Cambridge University Press. Received 3 August 2015; revised 13 October 2015; accepted 8 November 2015; first published online 23 November 2015. The authors would like to thank Professor H. Hornung for performing the Euler computations used in this work. Additional thanks are due to A. Kiani and J. Haggerty for their work machining the models and mount. Finally, the authors would like to thank B. Valiferdowsi for assistance in the laboratory. B.E.S. acknowledges the support of the Foster and Coco Stanback STEM Fellowship for his graduate studies.
Published - S0022112015006680a.pdf
Supplemental Material - Euler_movie.mov
Supplemental Material - Experiment_movie.avi