Unsteady simulation of marine controllable pitch propeller using boundary element method

Abstract

In this paper, flow around a submerged controllable pitch propeller is analyzed by developing a general 3D unsteady numerical model, based on boundary element method (BEM) in an infinite extended flow. BEM is combined with time stepping method to model the freely moving/unsteady trailing vortex sheet emanating from each blade trailing edge. In this way, the vortex blade–wake interaction can correctly be taken into consideration. As boundary integral equations are inherently unstable, a smoothing mollifier is applied to damp the singularity effect. Through this effort, attempt has been made to investigate the effect of blade rotation about its spindle on hydrodynamic performance of the controllable pitch propeller. For this reason, relative motion is applied on equation for each blade. This is the main novelty of the paper since little or no effort has been devoted to this subject, thus far. On the other hand, by using an unsteady time stepping method, the rollup wake pattern can be captured throughout simulation by changing the propeller pitching angle. It is demonstrated that the time stepping scheme combined by filtering method can successfully capture the rollup wake pattern during simulation time.