Co-Flow Jet Crescent-Shaped Airfoil for High-Thrust Wind Propulsion

Paper i proceeding, 2026

This paper numerically investigates Co-Flow Jet (CFJ) active flow control applied to a crescent-shaped wingsail airfoil over a range of angles of attack (AoA). A parametric study is conducted to study the effects of the jet momentum coefficient (Cμ), CFJ slot location, and slot size on improving wind propulsion performance. The objectives of the study are to maximize the thrust coefficient and energy savings while minimizing energy consumption of CFJ. A symmetric CFJ configuration is proposed to enable effective operation under wind from both port and starboard directions, with the injection and suction slots functioning interchangeably. The numerical simulation is conducted using Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations with k-ω shear stress transport (SST) model and is validated using an NACA 0015 airfoil at a Reynolds number of 0.36 million, corresponding to the model-scale condition. Results show that the configuration with a closer injection and suction location yields smaller CL enhancements but provides a larger stall margin. In contrast, increasing the slot size reduces the required control power but decreases the achievable lift enhancement. Considering the balance between the effectiveness (CL enhancement and CD reduction) and energy efficiency (PC required), the best CFJ crescent configuration places the injection slot at 15%C and the suction slot at 85%C, with both slots having a size of 1.4%C. At a Cμ of 0.1, the CFJ case can increase CL by 66% and reduce CD by 84% at a low PC with a 389% improved corrected aerodynamic efficiency ((CL/CD)c) as compared to the baseline case. Projecting this performance improvement to wingsail propulsion, the CFJ case achieves a 148% increase of thrust and 134% of power saving. Moreover, CFJ also reduces the force fluctuation that mitigates the root-mean-square-deviation (RMSD) of CL and CD by 93% and 79%, respectively.