The ground effect on the vortical flow formation and the aerodynamic characteristics of slender and double delta wings

The ground effect (GE) on the formation of the vortical flow over a slender and a double delta wing having a sweep angle of Λ=70° and 70°/40° was examined using Particle Image Velocimetry (PIV) and dye flow visualization methods in this study. Qualitatively and quantitatively measured results are shown for angles of attack, α=15° and 25° for double delta wing, and α=25° and 35° for slender delta wing in the side and cross-flow planes to reveal the details of the flow structure. The distance, h between the surfaces of the ground and the delta wing, which is normalized with the chord length of the double delta wing, c, was selected as h/c=0.1, 0.25 0.55, and the ground-free case (GFE). Also, the experiments were conducted at the chordwise location over the cross-flow plane at x/c=0.8 which was normalized with the chord length of the double delta wing, c. The Reynolds number was set as Re=2x104 for dye visualization and PIV experiments. For the experiments in the wind tunnel, the Reynolds number was taken as Re=1x105 within the various angles of attack 5°≤α≤45° and ground distances from GFE to h/c=0.55, 0.25, 0.10. The results demonstrate that the magnitudes of the vortices progressively diminish when the delta wing moves from the free-stream flow region into the boundary layer region close to the ground surface, h/c=0.1. The efficiency of the wing aerodynamics is positively affected by its closeness to the ground due to the dynamic air cushion.