Experimental study of effects of multi-winglets and tip blowing upon wingtip vortex

The effects of multi-winglets and wingtip blowing on the wing tip vortex are exper-imentally studied.On the basis of those results,a wing tip vortex control strategy which com-bines multi-winglets and tip blowing is proposed and justified.The experiments have been con-ducted at a low speed wind tunnel.The basic wing model is a rectangular NACA 0015 airfoil. Reynolds number (Re)defined by the chord length of wing and the free flow speed is 5.3×104 . The blowing coefficient (Cμ)defined by the momentum ratio of blowing to free flow is 0.017. The results show that the multi-winglets divide the wing tip vortex into several co-rotating vorti-ces which decreases the effect of the downwash flow generated by wingtip vortex,and thus im-prove the quality of the local flow.The lift coefficient increases forα>4°.The maximum lift co-efficient increases up to 1 2 .3%.Blowing strengthens the “wandering”of vortex core to change the position of the tip vortex.Blowing suppresses the formation of the wingtip vortex to some ex-tent.The joint control strategies have achieved a well control effect,meanwhile,the blowing en-hances the interaction of the co-rotating vortices.The peak of mean instantaneous vorticity is de-creased by 37% compared with the individual “+0-”multi-winglets configuration,and by 79%compared with the basic wing.The control effect of the joint strategy is subjected to whether the blowing could enhance the interaction of the co-rotating vortices or not.The moving direction of wingtip vortex also has a substantial influence on the control effects.