Effect of rudder on propulsion performance and structural deformation of composite propellers

A vessel's rudder interferes with the wake field of the composite propeller, which in turn affects not only the propulsion performance but also the structural deformation. To analyse the effect of the rudder on the composite propeller, a computational fluid dynamics (CFD) combined with finite element method (FEM)'s fluid-solid interaction (FSI) numerical method for calculating the composite propeller-rudder system (CPRS) was developed and verified. Analysis of the propulsion performance shows that the rudder can improve the propulsion efficiency of composite propellers. Such improvement also occurs with rigid propellers; however, the degree of efficiency improvement is higher for composite propellers. Analysis of structural deformation showed larger displacement; however, this does not lead to efficiency induction. The blade has a unique bend-twist coupling characteristics (i.e., the deformation of the bend is combined with a passive twist); changing the direction of the twist while changing the advance coefficient can improve efficiency. In addition, we analysed the effect of the propeller-rudder distance and the angle on the composite propellers. Considering energy saving and fatigue reduction, a propeller-rudder distance of 0.525D or an angle of 30 degrees are favourable.