Efficient Numerical Quantification of Flettner Rotor Installations

Abstract: This paper introduces an inviscid Computational Fluid Dynamics (CFD) approach for the rapid aerodynamic assessment of Flettner rotor systems on ships. The method relies on the Eulerian flow equations, approximated utilizing a state-of-the-art Finite Volume Method with a dynamic momentum source term to enforce rotor circulation. The method offers substantial computational savings by avoiding near-wall refinement and easing time step constraints, making it ideal for early design phases such as design space exploration. Validation against potential flow theory and viscous reference simulations confirms that the method reliably predicts lift-induced forces despite its limitations in capturing parasitic drag. Three-dimensional simulations, including idealized wind tunnel setups and full-scale ship applications at high Reynolds numbers (up to ReL=1E08), demonstrate that results based on low-order convection featuring a solid numerical viscosity yield deviations with respect to viscous reference data of around O(10%). Accepting this reasonable loss of predictive accuracy provides a simulation framework with response times in the order of minutes compared to hours or even days.