Mapping noise and efficiency for marine propeller designs

The primary aim of a marine propeller is to propel a ship to a given speed. Other desirable objectives might then be to do this as quietly, and as efficiently as possible. This paper presents a general framework for mapping out the noise and efficiency space as we vary gross propeller design parameters such as diameter, blade area or pitch-diameter ratios. For propellers, thrust and efficiency are usually presented as functions of advance ratio, and may be estimated using computational methods, theoretical expressions or curves derived from experiments such as those for the Wageningen B-Series. In the test framework, we maintain the desired ship speed and the corresponding thrust as a fixed overarching requirement. This essentially determines an advance ratio for each potential propeller in a large pool of randomly generated designs. Propellers which cannot deliver the required thrust are discarded. We may insert other criteria such as cavitation onset or material stress conditions to further refine the pool of potential designs before generating a noise estimate for each remaining propeller. In this work, an empirical radiated propeller flow noise estimate is used as the noise criteria. It is demonstrated that, even in this highly idealised setting, efficiency and noise have a complicated trade-off space.