Wingtip Jets Effects on Flow Entrainment and Aerodynamic Loads

This work presents experimental and computational investigations of effects of wingtip jets on flow and aerodynamic loads. Wind tunnel experiments were conducted using NACA 0012 wing model with an internal flow chamber and jet slots at the tip. Tests were carried out at 5, 10, and 15 m/s and at an angle of attack of 7.5 degrees. Average aerodynamic forces and moments were recorded using six-component external balance. To complement the experimental approach, studies were performed using computational fluid dynamics (CFD) of the blowing jet near wingtips to better understand the effects on the flow field and wing performance. These simulations were performed using a compressible Reynold’s Averaged Navier-Stokes (RANS) solver and investigated similar conditions used in the experimental setup. 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.