Numerical simulation of the flowfield of an airfoil in dynamic ground effect

An NACA4412 airfoil moving toward the ground is simulated numerically using computational fluid dynamics (CFD). First, the differences in the aerodynamic forces between dynamic ground effect (DGE) and static ground effect (SGE) are computed and analyzed. Next, the pressure distribution and the flowfield structure in DGE are studied in detail to understand the physical mechanisms. In region DGE 1, the lift in DGE is equal to that in SGE with the same angle of attack and does not change with the ride height. This region is out of ground effect, and the main physics that governs the flow is the angle-of-attack correction induced by the sinking movement. In region DGE 2, the lift in DGE is almost equal to that in SGE with the same angle of attack, and it increases with decreasing ride height. It is because of the pressure increase on the lower surface of the airfoil. The main factors that govern the flow are both SGE and angle-of-attack correction. In region DGE 3, the lift in DGE gradually becomes larger than that in SGE with the same angle of attack when the ride height decreases.