Rapid Aerodynamic Assessment of Flettner Rotor Installations Using an Inviscid CFD Approach

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 Euler equations combined with a dynamic momentum source term to enforce rotor circulation. By avoiding near-wall refinement and relaxing time-step constraints, the approach significantly reduces computational effort, making it particularly suitable for early-stage design tasks such as parametric studies and design space exploration. Validation against potential flow theory and viscous reference simulations shows that the method captures lift-induced forces and overall aerodynamic trends reliably. The level of agreement with viscous reference data depends on the operating conditions and numerical setup. While moderate deviations are observed for lower spinning ratios and dissipative convection schemes, larger discrepancies occur at higher spinning ratios and with low-diffusion schemes, particularly in the prediction of drag and peak lift. Three-dimensional simulations, including idealized wind tunnel setups, rotor-rotor interactions, and full-scale ship applications, demonstrate that the method provides consistent qualitative trends and robust force estimates at a fraction of the computational cost of viscous CFD. This makes the approach well-suited as a fast screening tool in early design phases, where large parameter spaces must be evaluated efficiently.