Aerodynamics and flow physics of a two-element airfoil in ground effect

A new evolution method is proposed to study the ground effect (GE) of multi-element airfoils. The aerodynamic forces and flow physics of a typical two-element airfoil with Fowler flap in GE are studied using Computational Fluid Dynamics and the evolution method. The compressible Reynolds-Averaged Navier-Stokes (RANS) equations with Spalart-Allmaras (S-A) turbulence model are discretized using the finite volume method. The results show that the GE of a two-element airfoil includes four characteristics: (a) the angle of attack (AOA) effect controls the GE features of each element of the two-element airfoil as a single element airfoil; (b) the camber effect strengthens the reduction of effective AOA and limits the capability of lift enhancement of lower surface in GE; (c) the gap effect decreases speed and increases pressure for the airflow in the gap in GE; and (d) the deflection angle of flap effect simultaneously influences the camber effect, the gap effect and the GE characteristics of the flap as a single element airfoil.