A preliminary design theory for polyphase impellers in unbounded flow

The main role of preliminary design for supercavitating propellers is to supply the basic data for the final design, such as: the hydrodynamic pitch angle, the radial load distributions, the approximate cavity length and the distribution of cavity source strengths which will help determine the three dimensional cavity source distribution. For this purpose, the effective use of supercavitating cascade theory with lifting line theory is discussed together with influences of neighboring cavities on cavity drag, the hydrodynamic pitch angle, inflow retardation and the optimum pitch distribution of the propeller. The computer program developed is applied to several existing propeller models. The results show that propeller efficiency is predicted well but pitch distribution is a little larger than for the model. The results are analyzed and compared with the results of a lifting surface design method which was developed for use with the preliminary design method.