Prediction Method for Hull Surface Force Induced by a Marine Propeller

Abstract

Cavitation is usually generated on propeller blades rotating in a ship wake, and it can dramatically increase the fluctuating pressure on the hull surface. So, it is important to estimate pressure corrctly. In the present paper, the following three methods are used to make a quasi-steady estimation of the cavitation: (1) A two-dimensional linearized cavity flow theory is applied to the equivalent hydrofoil section determined by Hanaoka-Koyama's unsteady propeller theory. (2) The cavity extent is given by measured cavity pattern on propeller blades. (3) The cavity extent is obtained by the so-called "Lift Equivalent Method" which is based on the pressure distribution determined by Hanaoka-Koyama's unsteady propeller theory and Moriya's two-dimensional hydrofoil theory. In the method (2) and (3), the cavity shape is determined by using the cavity shape-extent relation for the steady cavity which is derived by the above-mentioned two-dimensional cavity theory. And, on Huse's theory, fluctuating hull surface pressure in cavitating state is obtained based on these different estimation methods for cavitation, and the mutual comparisons are made. The "Lift Equivalent Method" seems to give more promissing fluctuating pressure than the linearized cavity flow theory.