Effect of Ground Boundary Condition on Aerodynamics of a Non-Slender Delta Wing in Static Ground Effect

Aerodynamics of a non-slender delta wing in static ground effect was studied in a low-speed wind tunnel. Ground boundary conditions in static ground effect at three different fidelity levels including a fixed flat plate, tunnel floor (belt off), and dynamic ground condition with a moving belt mechanism (belt on) were characterized using surface pressure measurements and force measurements. The findings suggest that the aerodynamic performance and longitudinal static stability exhibit significant differences in static and dynamic boundary conditions. In dynamic ground condition, the lift-to-drag ratio versus angle of attack curve shows a larger area underneath compared to out of ground cases, rather than increased peak values observed in static ground conditions. Considering the belt on and off cases, the slopes of the aerodynamic coefficients are reduced compared to the static ground condition (a fixed flat plate), which in turn, result in different positions of the aerodynamic center along the longitudinal axis. It is possible that changes in dynamic pressure loss and flow angularity caused by the ground boundary condition are the main factors contributing to these altered stability characteristics.