Effects of Perturbed Flow on the Stability of a Cavity's Boundaries

Drag reduction has made supercavitation very popular. One of the most important issues in supercavitation is its stability and control. It would be unsuitable if cavity closure occurs on a body resulting in some instability. Current work focuses on the nature of cavity instability and thus it was required to apply a dynamical model for such flow simulation. Using source and sink model attributes implemented in this study had some modifications. Semi-Hill vortex, as an impulse disturbance, was inserted into the Navier-Stokes equations to investigate the cavity instability. Finally, image processing technique was used to study the instability effects on cavity boundary and was found that a convective instability exists on the boundary of the cavity. Instability analysis on cavities of different lengths revealed that longer cavities are more sensitive to the disturbances. Hence, existing natural disturbances in a cavitating flow makes a long cavity boundary to fluctuate and finally collapse. This is the main reason that long cavities are not seen in nature.