UNSTEADY AERODYNAMIC CHARACTERISTICS OF A DUAL-ELEMENT AIRFOIL

Unsteady aerodynamic behavior and load characteristics of a VR-7 slat/airfoil combination oscillating sinusoidally between 5-25 deg have been studied. The unsteady, compressible Navier-Stokes equations are solved on a multiblock grid using an approximate factorization finite difference scheme. In the case of a single airfoil, a massive flow separation and formation of a strong vortex is observed. The vortex-induced suction and the shedding of the vortex into the wake is responsible for high aerodynamic loads and the subsequent stall of the airfoil. In the case of a slat/airfoil combination, the suction peak at the leading edge of the airfoil is reduced significantly in comparison to the single airfoil. Flow separation is confined to the trailing edge of the main airfoil, and the formation of a strong vortical structure is not observed. The slat/airfoil combination does not experience a massive flow separation, and the aerodynamic lift does not undergo the characteristic deep dynamic stall hysteresis loops.