Aerodynamic characteristics and stall behavior study of co-flow jet airfoil

The co-flow jet (CFJ), as a novel active flow control technique, has demonstrated significant potential in enhancing aerodynamic performance and suppressing flow separation. However, existing studies have largely focused on validating the performance improvement of airfoils, while investigations into its aerodynamic characteristics, flow separation behavior, and stall development remain relatively limited. This study applies the Reynolds-averaged Navier–Stokes equations with the Spalart–Allmaras turbulence model to investigate the aerodynamic characteristics, flow separation, and stall development of a CFJ airfoil in both CFJ-off and CFJ-on states. Furthermore, the influence of different jet momentum coefficients on aerodynamic performance is explored. The results indicate that, once the CFJ is activated, two distinct stall modes are observed: suction-slot bubble stall and leading-edge bubble stall. A small jet momentum coefficient can improve pre-stall aerodynamic performance but also increases the risk of earlier stall. Different jet momentum coefficients show their best corrected aerodynamic performance in different angle-of-attack ranges. This study advances the understanding of the CFJ flow control mechanism and supplies theoretical support for its application in aerodynamic optimization design and engineering practice.