Enhanced design performance prediction methods for rudders operating downstream of a propeller

Using a design spiral philosophy, methods have been developed and employed to predict rudder performance downstream of a propeller. The result of this work has been the development of a proven methodology that accounts for the physical basis of the interaction between the rudder and propeller of a ship.The principal factors in rudder-propeller interaction have been assessed and a coherent presentation system for quantifying rudder and propeller performance has been discussed. Systematic experimental tests on a skeg-rudder and all-movable rudder downstream of a propeller have been carried out in a 3.5m by 2.5m low speed wind tunnel and an open laboratory. Results for the ship bollard pull condition and a further range of propeller thrust loading have been presented and discussed. The data created in experimental work has been harnessed with physical understanding through analytical interpretation to create an interpolation and correction method for predicting rudder performance with the upstream influence of a propeller in the form of a software program. A finding of the work has been a method for accurately predicting performance data at any propeller thrust loading from rudder free stream (2-D sectional lift coefficient) and bollard pull performance data. For detailed analysis of the flow regime of rudder propeller interaction computational fluid dynamics in the form of a surface panel method has been investigated as a tool to provide detailed design information on a skeg-rudder operating downstream of a propeller. By way of example several design investigations are presented using the aforementioned analysis methods.