Numerical investigations of aerodynamic performance for flettner rotors in the presence of full-scale ship-rotor interaction

This study presents numerical investigations of aerodynamic characteristics (lift and drag coefficients) for Flettner rotors in the presence of the interaction between the rotor and the full-scale merchant ship. For this purpose, several numerical investigations have been conducted for two different isolated rotors in model and full-scale conditions using Reynolds Averaged Navier-Stokes (RANS) based Computational Fluid Dynamics (CFD) approaches. The effects of different turbulence models, mesh types and sizes, and boundary conditions on the domain's bottom surface have been investigated for a reference rotor in isolation and model-scale conditions. After that, selected methods were implemented on a full-scale isolated rotor geometry. The results of the computations were compared with experimental and computational results from the open literature and showed good agreement. As a result of the validation studies in isolated conditions, a similar CFD approach was applied on a full-scale rotor, which is operating on a capsize bulk carrier (merchant ship) to investigate the interaction between the rotor and the ship. During these numerical calculations, different ship and wind speeds, rotation rates for rotor and Thom, and also different wind profiles such as Straight and Atmospheric Boundary Layer (ABL) were investigated for the Flettner rotors in interaction with the full-scale ship. In conclusion, not only the aerodynamic characteristics of the Flettner rotor but also the effects of this complex interaction between the rotor and ship were analysed and investigated computationally. Results show that rotor-ship interaction significantly affects aerodynamic performance at spin ratios above 3, with drag forces increasing and lift forces decreasing compared to isolated conditions. Moreover, ABL profiles consistently led to lower lift coefficients than uniform wind conditions, underlining the importance of realistic environmental modeling.