Influence of roughness on propeller performance with a view to mitigating tip vortex cavitation

Abstract

This study explored the effects of uniformly and non-uniformly distributed biofouling roughness on hydrodynamic performance, particularly on the tip vortex cavitation (TVC) for model and full-scale marine propellers. The effect of roughness was investigated on a benchmark propeller belongs to the research catamaran, ‘The Princess Royal’. The investigation also explored the potential use of the roughness effect to mitigate this propeller's tip vortex cavitation with uniform, inclined and non-uniform flow conditions. In the numerical calculations, DES (Detached Eddy Simulation) approach was used to simulate the cavitating flow around the propeller. The Schneer-Sauer cavitation model was used to model the sheet and tip vortex cavitation. An advanced meshing technique called V-AMR (Vorticity-based Adaptive Mesh Refinement) was proposed to model the TVC in the propeller slipstream. The modified wall-function approach was utilised to implement the roughness effects in the calculations using the experimentally obtained roughness functions based on one of the authors' recent study. The results showed that the velocity components decreased inside the tip vortex due to roughness, resulting in a pressure increase and TVC mitigation. The suction side of the propeller blade tips was found to be an effective roughness application area for the TVC mitigation with a moderate level of loss in the propeller efficiency. The findings indicated that the cavitation volume reduction, mainly due to the TVC mitigation, was by approximately 6–38%, with a 5–10% efficiency loss in the model scale, while these figures were 4–10% and 2–5%, respectively, for the full-scale propeller under the uniform and non-uniform flow conditions.