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Languages : en
Pages : 7
Book Description
We report progress in our ongoing effort to compute and understand the three-dimensional instabilities (resonance) of open cavity flows from incompressible to supersonic speeds. In particular, our work is aimed at regimes where significant interactions occur between the shear layer spanning the cavity and the recirculating flow within the cavity, as encountered in many experiments and numerical simulations reported in the literature. Complementary methodologies for extracting information about global instabilities (including their receptivity and optimal control) of two- and three-dimensional cavity flows have been developed. We present here some sample calculations that show that for a low Mach number cavity with a length-to-depth ratio of two, the two-dimensional steady flow is unstable to three-dimensional (spanwise homogeneous) disturbances that consist of spanwise modulation of the recirculating vortex interior to the cavity. The oscillations are unstable over a narrow band of spanwise wavelengths comparable to the cavity depth. They are oscillatory in time, but with a very slow frequency that is about ten times slower than the incipient two-dimensional Rossiter instability. Instability seems to be related to cellular patterns observed in surface streamline patterns on cavity bottoms in some previous experiments.
