SINOPSIS

A set of integral equations for low-disturbed flow around two-dimensional supercavitating and ventilated oscillating hydrofoils under a free surface is obtained. A method to calculate time dependence of the unsteady cavity length by numerical solving the nonlinear equation of gas mass in the cavity balance (or the equation of the cavity pressure to be constant for vapor supercavities) is proposed. It is shown that approach to a free surface results in decreasing relative amplitudes of oscillations of the cavity length and hydrodynamic forces. Taking account of the variable cavity length results in smoothing frequency responses of forces in comparison with calculation when the cavity length is constant.