Effect of bleeding on aerodynamics of non-slender delta wing in ground effect

This article experimentally investigates the influence of the passive bleeding technique on the flow structure and aerodynamic coefficients of a non-slender delta wing with a 45-degree sweep angle in Static Ground Effect (SGE). The study was conducted under both static and dynamic boundary conditions using a fixed plate and a moving belt, respectively. Particle Image Velocimetry (PIV) and force/moment measurements were performed in a low-speed wind tunnel at Reynolds number, Re = 9 × 10⁴. The results indicate that bleeding in ground effect shifts the focal point toward the leading-edge and increases inboard/outboard vorticity at low angle of attack α = 6°, which may enhance the shear-layer feeding mechanism. At high angle of attack α = 17°, bleeding in ground effect reduces the adverse effects introduced by the ground proximity, potentially delaying stall. Regarding aerodynamic coefficients, bleeding overall reduces their sensitivity to the ground. In addition, the dynamic boundary condition results in decreased magnitudes of the aerodynamic coefficients and does not negatively affect the stall angle delay provided by the bleeding mechanism, unlike the static boundary condition.