Abstract: The optimal pitch of a locked controllable pitch propeller corresponding to minimal additional drag and minimal hydrodynamic moment was investigated by means of computational fluid dynamics for a ship that is propelled by part of propellers. A typical fiveblade controllable pitch propeller was calculated numerically to gain the characteristics of additional drag and hydrodynamic moment as functions of its pitch and advance velocity. The numerical calculations are based on finite volume method. The RANS equations of the 3D incompressible viscous flows are solved iteratively to simulate the flow behavior around the propeller. The calculation results show: ① The additional drag of the locked propeller is maximal when the propeller is set on maximal ahead pitch, which accounts for about 80% of the hull resistance at the same speed. The value of hydrodynamic moment also reaches maximum; ②The additional drag of the locked propeller is minimal when the propeller is set on maximal astern pitch, which accounts for about 50% of the hull resistance at the same speed. The hydrodynamic moment decrease markedly compared with the maximal ahead pitch; ③At zero pitch the additional drag lies between maximal ahead pitch and maximal astern pitch, and the hydrodynamic moment is very small which comes close to zero. These conclusions are helpful for marine engineers not only to determine joint control curve of the propulsion plant for the operating condition that the ship is propelled by part of propellers, but also to design the shaft brake rightly.

Key words: computational fluid dynamics, controllable pitch propeller, locked shaft, additional resistance