Control of flow structure over a non-slender delta wing using passive bleeding

Abstract

Recently, it has been demonstrated that the bleeding, which utilizes passages inside the wing to allow the fluid flowing from the pressure side to the suction side by using inherent pressure difference, could be used as an effective flow control method for non-slender delta wings. In the present study, this technique is applied to a non-slender delta wing with sweep angle of Λ=45 deg with particular interests in delaying stall and eradication of three-dimensional surface separation. The experiments are conducted in a low speed wind tunnel using surface pressure measurements, Particle Image Velocimetry (PIV) measurements on near surface and cross flow planes, and aerodynamic force measurements. The bleeding passage orientation defined as back angle θ and bleeding passage size defined as bleed opening ratio bor are varied and the corresponding wings along with the Base planform are tested for the Reynolds numbers 35000≤Re≤100000 and the angles of attack 0≤α≤36 deg. The results indicate that at sufficiently high angle of attack where the pronounced surface separation appears on the Base planform, which is indicated by focus point along with large-scale swirl in the near surface streamline pattern, the elimination of surface separation is achieved with passive bleeding. This is incorporated with significant increases in the magnitudes of surface normal vorticity and suction pressure coefficient −Cp, which indicate recovery of leading-edge vortex. Considering the back angle and bleed opening ratio, the results indicate that increases in both parameters provide better performances in terms of elimination of surface separation. In addition, aerodynamic coefficient measurements show that proper bleeding configuration provides significant improvement in stall angle and lift coefficients.