Some Characteristics of a Partially Cavitating Hydrofoil

Abstract

Cavitation is one of the most important problems in the field of ship hydrodynamics. It is almost unavoidable phenomena for heavily loaded screw propellers. In spite of many investigations that have been carried out for a long time, there are many problems left to be pursued. Especially quantitative explanations of cavitation are lacking or left vague.
An experimental research on the steady state cavitation on a two-dimensional hydrofoil was undertaken at the cavitation tunnel of Tokyo University. We have aimed at adding some experimental data, emphasizing the importance of pressure distribution itself rather than the total force or moment acting on a hydrofoil. To this end local pressures at four points on the suction side of the profile were measured and compared with calculation.
Conclusions obtained are as follows.
1) A complicated type of cavitation named “activated sheet cavitation” occurs and plays a significant part as far as a two-dimensional hydrofoil at high angle of attack is concerned.
2) Pressure distributions in the wetted area are scarcely affected by the presence of partial cavitation that covers the fore surface of a hydrofoil.
3) The pressure at the rear end of cavity does not reach the stagnation pressure, and the reduction of C_P is less than 20 percent of the non-cavitating C_P.
4) Mathematical model of cavity that the rear part of cavity is represented by a distribution of weak sink shows fairly good agreement with experiment.