Experimental and Numerical Investigations of Flow Entrainment and Aerodynamic Performance for Small Aspect Ratio Wings with Wingtip Jets

Wind tunnel and CFD experiments were conducted using a NACA 0012 wing model to investigate effects of wingtip jets on flow and aerodynamic loads. Tests were conducted at 5, 10, and 15 m/s at 7.5° angle of attack. Average aerodynamic forces and moments were obtained using a six-component external balance. CFD simulations were performed using the RANS solver to investigate conditions similar to the physical experiment. This was done to better understand the effects on the flow field and wing performance.

Changes in spanwise velocity show critical differences between the jet on and off cases and provide insight into the difference in lift. The jet causes a negligible change to the spanwise velocity below the airfoil, and significantly reduces and even reverses the spanwise velocity above the airfoil. This reversal of the spanwise flow is due to the air entrainment caused by the jet. Under the steady blowing, the wingtip vortex is displaced upward and outward from the wingtip.

Results show that the blowing jet from the wingtip reduces the pressure on the top of the wing whereas the effect on the pressure on the bottom of the wing is minimal. Observed changes in pressure distribution explain forces and moments changes, specifically the total lift and drag increase.