A BEM for the modeling of unsteady propeller sheet cavitation inside of a cavitation tunnel

Abstract

A boundary element method is applied to predict the unsteady cavitating performance of marine propellers subject to a non-axisymmetric inflow with the complete tunnel wall effect. The tunnel and propeller problem is solved directly to predict the fully unsteady performance of the cavitating propeller. The cavitation on blade and wake surface is determined by applying the dynamic and the kinematic boundary conditions on the cavity surface. The potential on the cavity surface is known from the dynamic boundary condition and the relation between cavitation number and cavity velocity. Once the boundary value problem is solved for the unknowns-the potentials on the wetted blade surface and the normal derivative of potentials on the cavity surface -the new cavity shape is adjusted by using the normal derivative of the potential. The potential on the new cavity surface is determined by using the kinematic boundary condition on the cavity. The procedure is repeated until the cavity shape converges and the pressure on the cavity becomes constant. To validate the present method, the effects of the number of blade panels and the dimensions of the tunnel walls on blade forces are presented. The predicted cavity patterns are compared with those observed from experiment.

Blockage effect influence on model-scale marine propeller performance and cavitation pattern

“…Watanabe and Brennen (2003) investigates the unsteady dynamics and instabilities of cavitating propellers operating in a cavitation tunnel, analyzing the effect of tunnel walls on the promotion of the surge of instabilities. Lee and Kinnas (2005) applies the boundary element method to a marine propeller subject to a non-axisymmetric inflow with the blockage effect. Besides the increase of thrust and torque coefficients, the blockage effect also affects the volume of cavitation.…”

Marine propeller parametric optimisation and matching to electric motor

“…Two approaches are usually applied in propeller design: mathematical methods based on circulation theory and systematic series of propellers [1]. The former regards lifting line, lifting surface, vortex-lattice and boundary element method; examples are given in [2][3][4]. The latter is widely used in the preliminary design of light and moderately loaded propellers [5].…”