The steady flows and hydrodynamic performances of a propeller without and with the Propeller Boss Cap Fins (PBCFs) are simulated by solving the Reynolds-averaged Navier-Stokes (RANS) equations using the software package STAR-CCM+. To determine a suitable grid setting, a grid convergence study is carried out first by changing the grid sizes separately in the sub-domains enclosing the propeller blades and the PBCFs. The CFD investigation into the energy-saving rate of the PBCFs with systematically varied section profiles at model-scale shows the PBCFs with modified ‘NACA M7’ section geometry performs better than the flat plate in energy-saving effect. Full-scale simulations are also carried out using typical PBCF geometries investigated at model scale, and the results are compared with model-scale ones to evaluate the Reynolds scale effects on the energy-saving rate. The hydrodynamic forces acting on the propeller blades, the PBCFs, and the boss cap are compared to explore the mechanism behind the scale effects on the PBCFs. The study indicates that the scale effect positively influences the energy-saving effect of all the PBCFs investigated, while the flat-plate PBCFs benefit more from the scale effect
