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In the present work, Comparison of Energy Efficiency Performance between a twisted rudder and an ordinary spade rudder is conducted during self-propulsion. The energy-saving mechanism of twisted rudder is revealed by numerical simulation. This study is carried out using our solver naoe-FOAM-SJTU. The governing equations are unsteady Reynolds-Averaged Navier-Stokes (URANS) equations discretized by finite volume method (FVM). Overset technique is employed to handle the propeller rotation. To prepare for self-propulsion simulations, the open water curves of propeller and bare hull resistance are previously obtained by our solver. These two results show good agreement with experimental data. Based on that, the self-propulsion simulations to estimate the speed performance with twisted rudder and spade rudder are carried out. The results show that twisted rudder boosted hull efficiency by 2.4% through reducing the thrust deduction fraction and raising the hull efficiency. The delivered power is also decreased by 3.9% in the model scale comparing with ordinary rudder. The flow field around the propeller- rudder system shows that twisted rudder efficiently retrieves y-direction momentum to x-direction and improves the propulsive performance.

 

twisted rudder; self-propulsion; overset grids; naoe-FOAM-SJTU solver