Unsteady Gaseous Diffusion Associated With a Fully Cavitating Oscillating Flat-Plate Hydrofoil

Abstract

This paper gives an analysis of convective gaseous diffusion into a full cavity behind an oscillating flat-plate hydrofoil in a turbulent flow. The unsteady diffusion theory accounts for fluctuations of cavity gas pressure and length which are assumed to be harmonic oscillations but are not necessarily in phase with the hydrofoil motion. A diffusive lag function is found which, for a given reduced frequency, determines the instantaneous diffusion rate as a product of the lag function and the quasisteady mass diffusion. The present results can be used to study the rate of gas entrainment from the cavity into the wake behind the oscillating cavity.