Performance Enhancement of Multiple Wingsail Airfoils Using Co-flow Jet Active Flow Control

Paper i proceeding, 2025

This paper numerically implements Co-flow Jet (CFJ) active flow control (AFC) on multiple wingsail airfoils to improve their aerodynamic performance at three apparent wind angles (AWA), 30◦, 90◦, and 150◦, representing the typical sailing conditions of close hauled, beam reach, and broad reach, respectively. The goal is to maximize the thrust coefficient (CT) improvement at the minimum energy consumption. The 2D Unsteady Reynolds averaged Navier-Stokes (URANS) simulation with a two equation k-ω shear stress transport (SST) turbulence model is utilized. Numerical validation is conducted on a single wingsail airfoil by comparing the lift coefficient (CL), drag coefficient (CD), and pressure coefficient (Cp) distributions with those of experiments. Good agreement is achieved for the AoA below 15◦, whereas more discrepancy occurs in higher AoA due to the URANS’s deficiency in predicting massively separated flow at deep stall. The multiple wingsail cases have three wingsails in total. At AWA of 30◦, wingsails interact with each other vigorously through the downwash and the upwash effects. To make full use of such interaction for performance improvement, a flow control strategy combining the distribution of jet momentum coefficient (Cµ) with the optimization of the wingsail’s AoA is proposed. As a result, the CFJ case achieves the CT improvement by 89% compared to the baseline. At the AWA of 90◦, the interaction effect is alleviated as wingsails are located in the same streamwise location. The CT is improved by 108% by CFJ due to the desirable AWA of 90◦ for sailing and thrust generation. In the AWA of 150◦, both CD and CL contribute positively to thrust. Redistribution of Cµ has a more significant role in increasing CFJ energy efficiency than optimizing the overall thrust. A CT improvement of 136% is achieved by CFJ wingsails at this AWA.