PROPELLER DESIGN AND ANALYSIS BASED ON NUMERICAL LIFTING-SURFACE CALCULATION

Marine propellers have been designed by using the design charts based on methodical series tests. In the recent years however, propellers with various bled geometrics such as a highly skewed propeller are often fitted to ships in order to reduce the propeller induced vibration and noise, or to improve the propulsive performance of the propeller. In the design of such propellers, the design charts based on methodical series tests are to be supplemented by the theoretical calculations of propeller design and the accurate estimation of propeller open water characteristics. Further, non-uniformity of ship's stern flow produces the fluctuation of the pressure distribution on the propeller blades, giving rise to the unsteady propeller shaft forces and the unsteady cavitation on the blades. Time variation of the extent and volume of the unsteady cavity is a principal source for the generation of hull pressure fluctuations and the radiation of noise (Hoshino 1, 1982). Deeper understanding of such unsteady flow phenomena on the propeller blades is indispensable for the reliable estimation of the propeller induced vibratory forces at the design stage and for the determination of appropriate countermeasure, if necessary. The present paper describes the numerical methods to design such propellers and analyse the steady and unsteady characteristics of the propellers by using a propeller lifting surface theory.