High Efficiency Co-Flow Jet Wingsail Airfoil for Sustainable Maritime Transportation

This paper studies Co-Flow Jet (CFJ) active flow control (AFC) on a NACA 0015 wingsail airfoil to improve its performance at various angles of attack (AoA). The objective is to enhance lift at minimal energy expenditure for maximizing thrust and net power saving of the wingsail. The parametric study is conducted on the jet momentum coefficient (Cµ), and various locations and sizes of the injection and suction slots. The 2D Unsteady Reynolds Averaged Navier-Stokes (URANS) simulation is conducted with a two-equation k-ω shear stress transport (SST) turbulence model and a Gamma-ReTheta (γ−Reθ) transition model. Numerical validation is conducted on the NACA 0015 airfoil by comparing the lift coefficient (CL) and drag coefficient (CD) with those of experiments, which achieves a good agreement up to the post-stall condition of 17° AoA. From the parametric study of CFJ location and size, the optimized design has the injection slot size of 0.5%C located at 3%C and a suction slot size of 1.2%C located at 85%C. Compared to the baseline airfoil with the maximum CL acquired at 15° AoA, the optimum CFJ airfoil is able to extend the stall AoA to 24° and achieve a CL increase of 122% and a CD reduction of 24%. Using the optimized CFJ wingsail airfoil for ship propulsion, the net power saving is increased by 111% as compared to the baseline wingsail at an apparent wind angle (AWA) of 90°. Furthermore, the practical energy saving of the wingsail is evaluated along three representative shipping routes using the real-world wind and operation data. Depending on the selected route, the CFJ wingsail can increase the energy savings by 63.3% to 109% as compared to the baseline wingsail, which corresponds to a 0.98% to 3.0% reduction of the total energy consumption over the routes.