Calculation of the pressure distribution on wing profiles in a flow of water with gas content

The paper is concerned with the two-dimensional steady and compressible flow of water with gas content around hydrofoils. The term gas means both the free air contained in water and the vapor resulting from cavitation. For the sake of simplicity we have neglected the movement of gas bubbles relative to the surrounding water. Therefore a unified velocity and pressure field is adopted. Besides, we have assumed that the mass ratio of gas to water is only a function of the local pressure. Following an efficient method of the theory of transonic gasdynamics, the pressure field around the profile is calculated solving a nonlinear integral equation. The theory is tested on some numerical examples. It turns out that the gas content in water gives remarkable differences in comparison with the incompressible pressure field only when, as a result of the low velocity of sound, local supersonic regions occur which end with shocks. A comparison with available experimental data shows at least a qualitative agreement with the theoretical results.