Calculation of Propeller Cavitation and Pressure Fluctuation on Ship Stern Using a Simple Surface Panel Method

Abstract

It is important to predict the unsteady cavity shape in order to calculate the pressure fluctuation induced by cavitating propeller. For the purpose of this, we had already developed the calculation method for unsteady cavitation on a marine propeller using a simplified surface panel method SQCM and presented the reasonable results with respect to the cavity volume and the cavity shape.In this paper, we present a calculation method for pressure fluctuation on a hull surface induced by cavitating propeller. In the present method, first, the variation of unsteady cavity shape is calculated. Next, hull surface flow and propeller flow are calculated simultaneously in order to calculate the pressure fluctuation on the hull surface including the interaction between hull and cavitating propeller. At that time, we change the cavity shape on blade section at each time step using calculated cavity shape. The boundary condition is zero normal velocity condition on not only the wetted surface but also the cavity surface. Namely, we deal with the cavity surface as the rigid surface and regard the variations of cavity shape as the variations of blade section.The calculated results of the fluctuating pressure, the amplitude and the phase are shown about two kinds of propellers and we compare the results with experimental data. Qualitative agreements are obtained between the calculated results and the experimental data about low order blade frequency component.