Note: ESDATSEA

Abstract: The accurate prediction of the propeller and rudder forces is crucial for an efficient design. While the calculation of transversal forces is of interest for manoeuvring, the prediction of the longitudinal forces and the propeller-rudder interaction gains in importance due to energy efficiency requirements. Therefore, this paper presents a method to quickly calculate the rudder forces including the bidirectional interaction between rudder and propeller. The method couples a lifting line approach with a panel method. The lifting line approach is used for the calculation of the propeller forces and for the initial calculation of the interaction. Thereafter, the results of the flow field are applied to the panel method which is used for the rudder force calculation. Afterwards, the result of the panel method is used to improve the inflow to the propeller in the lifting line. The paper validates the rudder force calculation and shows applications of the method in the design process.