Numerical study of scale effects on the open water performance of a rim-driven thruster

Abstract

This paper presents the study of scale effects on the open water performance of a rim-driven thruster (RDT) based on Computational Fluid Dynamics (CFD) simulations. For marine propellers, the effects of viscosity are often significant when there is a dramatic change in Reynolds number, which occurs when the results from model scale tests are extrapolated to propellers at full scale. Reynolds-Averaged Navier–Stokes (RANS) simulations with the Moving Reference Frame (MRF) approach are carried out in ANSYS Fluent for the RDTs under different working conditions. Considering the potential transitional flow on the propeller at model scale, the γ−Reθ transition model is adopted which can better resolve the boundary layer and yield more accurate results for transitional flows. From the simulations, it is observed that the duct and rim are more affected by the scale effects than the propeller. When the Reynolds number increases, there is a small amount of increment in the total thrust coefficient but a significant decrease in the total torque coefficient, resulting in a substantial improvement in hydrodynamic efficiency of the full scale RDT compared to the model scale.