Effect of flap strakes with regard to vortex wake alleviation

Abstract

Numerical simulations based on the three-dimensional Euler equations are used to investigate the nearfield bursting of the flap tip vortex of a narrow body airliner regarding vortex wake alleviation. Strake-like flap tip modifications with 80° and 70° backswept outer side-edge of the outboard flap are tested. The simulation quality of the vortex formation and spatial development is analysed by comparison to wind tunnel measurements of the spanwise lift distribution and to experimental five-hole-probe data. Very good agreement between measurement and computational results is achieved. Flap strakes are shown to be capable to trigger both bubble type vortex bursting and bursting above the suction side of the flap, leading to a wake-like flow structure. However, the flap vortex structure recovers shortly downstream of the bursting location. For the investigated high lift configuration the performed Euler computations do not give an indication that nearfield vortex bursting could lead to a reduction of circulation.