Investigations of Propeller-Rudder Clearance on Propulsion Performance and Flow Field in Vicinity of Propeller

Abstract

The presence of the propeller affects the hydrodynamics of the rudder in the same way that the ship's hull interferes with the function of the propeller behind and vice versa. Therefore, the arrangement of the propeller and rudder is very important in determining the overall ship propulsion performance. This paper presents a numerical analysis of the KCS propulsion system at various longitudinal clearances with respect to rudder position. The analysis was carried out in a full ship configuration using the KCS hull, propeller and rudder. The propeller clearance was varied based on the existing KCS design, design adjustments and recommendations from DNV respectively by 0.124D, 0.129D and 0.100D. Propeller performance was analysed based on individual variations, interactions between the propeller and rudder, as well as variations in the number of meshes of 0.5 mil, 1.0 mil, and 1.5 mil. The flow distribution around the propeller and the pressure distribution of the rudder inflow onto the rudder surface are also discussed. Numerical examination revealed that DNV's recommended clearance of 0.100D provided the best results and improved KCS propulsion performance compared to existing design. The mesh sensitivity analysis performed revealed that the recommended clearance showed excellent performance in all mesh variations. In response to these findings, modification of the KCS propeller clearance following DNV recommendations would be beneficial to improve overall ship performance.