Aerodynamic characteristics of a wing-in-ground effect with micro-vortex generators

Micro-vortex generators (MVGs) are simple passive flow control devices mounted on the base surfaces to mitigate the boundary layer flow separation. The effect of the MVGs installed on the aircraft lifting surfaces, i.e., wing, operating close to the ground (ground effect), is not well understood. In this work, the aerodynamic performance of a National Advisory Committee for Aeronautics (NACA) 4412 wing in ground effect equipped with MVGs is numerically investigated. Installed at 10% or 25% chord of the wing, the MVGs are arranged in a row in a counter-rotating pattern. The analysis is carried out at 18°angle of attack, which is close to the stall angle of attack of the wing. Four different cases of h/b = 0.1, 0.5, 1, and free flight (no ground effect) are considered in this analysis. The Reynolds number based on the wing chord is around 3 million. In this work, the detached eddy simulation (DES) method is employed to accurately capture the high energy levels of the vortex formed behind the MVGs, the wing tip vortex, and their contact with the ground. The DES simulations accurately depict the intricate flow dynamics of the NACA 4412 wing, and the use of MVGs enhances its performance while in close proximity to the ground. A negative Cp peak at the leading edge of the wing increases as it approaches the ground, according to the analysis. For h/b = 0.1, the lower wing over pressure is much higher than for other cases. The Q-criterion shows flow unsteadiness and wing tip vortex evolution. The flow region's vortical structures increase as the wing descends. The flow has the most coherent vortical forms at 0.1 aspect ratio. The ground effect leads to an increase in lift and a decrease in drag as the wing gets closer to the ground.