The computational fluids dynamics experts at ANSYS, Inc. and SVA (with Schiffbau-Versuchanstalt Potsdam GmbH) have a well-established relationship dedicated to using CFD to predict the interaction between the hull of a ship and its propeller. An area of specific interest for this partnership is focused upon improving understanding of the unsteady flow past the propeller as it rotates behind the ship. Computations with the different rotor-stator interaction methods available in CFX software have been undertaken, and demonstrated that the simulation of this flow with a true time-dependent rotor-stator interface provides a significantly higher level of accuracy than the usual steady-state simulations. This approach also permits prediction of the unsteady pressure fluctuations on the hull and on the rudder, which are a main source for noise and vibration within a ship.

Several joint projects resulted in the first ever simulation of a surface ship with rotating propeller. This study was, in large part, made possible due to the flexibility within CFX which made the creation of the rotor-stator interface possible by permitting topologically different grids to be connected and generating high quality meshes in the two regions with speed and ease.

The ability to take into consideration the behavior of the propeller in the numerical computation of the viscous flow on a ship hull introduces valuable new perspectives for improving hull designs. It is now possible to calculate the power required in order for the propeller to achieve a certain ship speed. Previously hull improvement studies have focused upon reducing hull resistance while neglecting to take into account the effect of the propeller on the flow and the interaction between the ship hull and the propeller. This has resulted in ship designs with low bare hull resistance but with high power requirements. It is possible to investigate the impact of improvements in both hull and propeller design simultaneously.

Wake-propeller interaction as test case for unsteady rotor-stator interface	Streamlines originating at different upstream locations and passing through the propeller region. The swirl introduced by the propeller is clearly visible.