Objectives  With the increasing popularity of the concept of green ships, marine hydrodynamic energy-saving technology has drawn more attention from researchers. This paper studies the way to reduce energy consumption of ships at sea.

  Methods  naoe-FOAM-SJTU solver independently developed by Prof. Wan Decheng's research team in Shanghai Jiao Tong University is used to numerically investigate the hydrodynamic characteristics of Propeller Boss Cap Fins (PBCF). In order to better investigate the interaction between PBCF and propeller, the influences of PBCF on blades, hubs and hub caps are studied respectively.

  Results  It is found that the hubs and hub caps are less affected by PBCF, and despite sharp reduction of the propeller torque, the influence of PBCF on the overall thrust is limited. Further it is found that the Reynolds number has great influence on the energy-saving characteristic of PBCF and has a critical value below which the increasing Reynolds number will give rise to greatly improved energy-saving effect, and above which, the energy-saving effect is basically unchanged. This shows that PBCF may have better energy-saving characteristics in the full scale which has the critical Reynolds number.

  Conclusions  The findings are satisfactory and shows that the naoe-FOAM-SJTU solver is feasible for the direct simulation of hydrodynamic characteristics of PBCF, and this research method can be applied to other energy-saving devices.