Hydrodynamic Modelling and Performance Evaluation of Cycling Varying Pitch Propeller in Non-Uniform Wake Field Using Open-Water RANS CFD Simulations

Abstract

The cyclic varying pitch propeller is a controllable pitch propeller that is able to change the pitch of the propeller blades individually during one revolution in order to compensate for the non-uniform wake field. By changing the pitch to compensate for the non-uniform wake field, the unsteady phenomena such as cavitation, vibration and noise can be reduced. This gives new possibilities when designing the propeller blades, which can result in a higher propeller efficiency. In order to make the blade design, the actuation mechanism and determing the optimum blade pitch trajectory, it is necessary to determine the hydrodynamic loads acting on the propeller blades due to the non-uniform wake field. An unsteady CFD simulation of the cyclic varying pitch propeller in a non-uniform wake field is computational expensive and is not suitable for determining the optimum pitch trajectory in an iterative manner. Hence, it is desired to have a less computational expensive method to calculate the optimum pitch trajectory. A simple method to characterize a propeller is to determine its open-water characteristics. It is therefore reasonable to try using the propellers open-water characteristics to determine the hydrodynamic loads in order to obtain a less computational expensive method. In this paper, the propellers open-water curves are determined for a range of pitch settings through steady state RANS CFD simulations. To avoid making an erroneous conclusion, the uncertainty of the simulation results are determined. The propellers open-water curves are used to evaluate the thrust and efficiency for the cyclic varying pitch propeller which are compared to the controllable pitch propeller.