Hydrodynamic Analysis of Propellers in Unsteady Flow Using a Surface Panel Method

A surface panel method for the analysis of propellers operating in non-uniform flow is described. The surface panel method which was originally developed for the analysis of steady propeller problems is extended to the unsteady propeller problems. The surface of propeller blade and hub is approximated by a number of small hyperboloidal quadrilateral panels with constant source and doublet distributions whose strengths are varying with time. The surface of trailing vortex sheet is also represented by hyperboloidal quadrilateral panels with constant doublet distributions whose strengths are changing along downstream direction. The strengths of source and doublet are determined by solving the boundary value problem at each time step. First, calculations were conducted for a one bladed propeller rotating impulsively from rest in a uniform flow to confirm the accuracy and the applicability of the present panel method. Next, the problems of the propellers operating in non-uniform flow were solved by the present method. The unsteady pressure distributions on the propeller blades calculated by the present method are in good agreement with the experimental data in full scale propellers. Further, it is shown that the fluctuating thrust of one blade and propeller shaft forces calculated by the present method agree well with experiments.