Ground effect on the aerodynamic parameters and flow characteristics of a non-slender delta wing

In this study, the ground effect on the flow structure and aerodynamic coefficients of the non-slender delta wing with a sweep angle of 40° was investigated experimentally. The flow visualization experiments were carried out at Reynolds numbers, Re=10^4 and 2x10^4 for various angles of attack, α and ground distances, h/c. The results demonstrated that the ground effect causes earlier vortex breakdown and more disordered and unsteady flow structure formed on the delta wing compared to the ground free case at the Reynolds number, Re= 10^4. But when Reynolds numbers, Re is increased from 10^4 to 2x10^4 value, the impact of the ground on the vortical flow structure and the vortex breakdown position is reduced and it has virtually no effect at angles of attack of α=8°, and 14°. For the wind tunnel experiments, the Reynolds number, Re was taken as, 1.296x10^5 at different angles of attack, α and ground distances, h/c. Results revealed that ground effect gives rise to higher lift coefficients, CL compared to the ground free case. The lift increment can be attributed to the RAM pressure effect and dynamic air cushion between ground and delta wing surface. The Particle Image Velocimetry (PIV) experiments were carried out to investigate the impact of the ground on the time-averaged streamline pattern, vorticity concentrations and velocity fluctuations at the Reynolds number, Re=15.73x10^3. Results displayed that the ground effect brings about outboard movement of primary vortices compared to ground free case. Also, the size of the primary vortices gets higher under the impact of the ground.