Numerical and experimental investigation of ship performance and hull-propeller-rudder interaction of a twin-propeller/twin-rudder ship with different angle

The change of rudder angle will change the surrounding flow field, resulting in different loads and interactions on the hull-propeller-rudder, which will affect the resistance and self-propulsion performance of the ship, and this effect will be amplified on the twin-propeller / twin-rudder ship. The CFD(Computational Fluid Dynamics) method is used to analyze the resistance of the ship-rudder at the rudder angle of 0 ° -8 °, the rudder lift, moment, axial wake, the rudder profile velocity vector at the propeller shaft height, and the dynamic pressure distribution on the inner and outer surfaces of the rudder. The resistance of the ship-rudder at different rudder angles is verified by the EFD(Experimental Fluid Dynamics) method. After installing the propeller, the self-propulsion performance of the hull-propeller-rudder with rudder angle of 0 ° -6 ° is calculated and analyzed by CFD method, and compared with the EFD results. The axial wake, the dynamic pressure on the surface of the propeller and rudder and the velocity vector near the rudder are analyzed, and the flow field and vorticity field of the hull-propeller-rudder are analyzed. The results show that : 1 ) When the ship-rudder is combined, the change of resistance is mainly reflected in the force change of the rudder in the flow field behind the stern. The CFD results show the same trend as the EFD results. When the rudder angle is 6 °, the total resistance of the ship-rudder is the smallest, and the resistance decreases by about 1%. 2 ) The change of rudder angle has little effect on the wake field in front, but it has a great influence on the flow field around the rudder, which in turn affects the resistance, lift and moment. 3 ) When the hull-propeller-rudder is combined, the self-propulsion performance is the best when the rudder angle is 4 °, and the self-propulsion power can decrease by about 4%. This is mainly due to the beneficial interaction between the propeller and the rudder. 4 ) The change of rudder angle has little effect on the surface pressure of the propeller, but it will slightly change the axial wake behind the propeller, and the surface dynamic pressure of the rudder is quite different. 5 ) When the rudder angle exceeds the optimal rudder angle of 4 °, the interaction between the hull-propeller-rudder becomes unfavorable, resulting in the chaos of the vorticity field and the overall performance degradation. For twin-propeller / twin-rudder, proper arrangement of rudder angle can effectively improve ship performance and achieve energy saving purpose.