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# The effect of flow oscillations on cavity drag

Gharib, M. and Roshko, A. (1987) The effect of flow oscillations on cavity drag. Journal of Fluid Mechanics, 177 . pp. 501-530. ISSN 0022-1120. https://resolver.caltech.edu/CaltechAUTHORS:GHAjfm87

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## Abstract

An experimental investigation of flow over an axisymmetric cavity shows that self-sustained, periodic oscillations of the cavity shear layer are associated with low cavity drag. In this low-drag mode the flow regulates itself to fix the mean-shear-layer stagnation point at the downstream corner. Above a critical value of the cavity width-to-depth ratio there is an abrupt and large increase of drag due to the onset of the ‘wake mode’ of instability. It is also shown by measurement of the momentum balance how the drag of the cavity is related to the state of the shear layer, as defined by the mean momentum transport $\rho\overline{u}\overline{v}$ and the Reynolds stress $\rho\overline{u^{\prime}v^{\prime}}$, and how these are related to the amplifying oscillations in the shear layer. The cavity shear layer is found to be different, in several respects, from a free shear layer.

Item Type:Article
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https://doi.org/10.1017/S002211208700106XDOIUNSPECIFIED
Additional Information:Copyright © 1987 Cambridge University Press. Reprinted with permission. (Received 11 March 1986 and in revised form 10 September 1986) The research described in this paper was carried out at the Jet Propulsion Laboratory, California Institute of Technology and was sponsored by the US Army Research Office and the National Aeronautics and Space Administration. Support was also received from the National Science Foundation. Valuable discussions of aspects of the research with V. Sarohia and D. Rockwell are also acknowledged.
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