Effect of Midwing Vortex Generators on V-22 Aircraft Forward-Flight Aerodynamics

Abstract

The effect of midwing vortex generatorson the V-22 aircraft forward-e ight (airplanemode )aerodynamics using computational e uid dynamics is investigated. The multizone Navier -Stokes method is applied to calculate the e ow over a V-22 wing -fuselage-nacelle cone guration in forward e ight with and without vortex generators. The calculations show that thevortex generatorsreduceseparation and producea favorableeffecton both lift and drag if they are properly designed and placed in the right position. The chordwise location and the incidence angle of the vortex generators are two important design variables in achieving the desired separation alleviation. development. 1i3 Acomprehensive reviewon the V-22 Osprey aero- dynamic development during the past 15 years is given by McVeigh et al. 4 The use of computational e uid dynamics (CFD) has been explored by the present author to analyze the complex aerodynam- ics of the V-22 aircraft. The overall e owe eld about the aircraft in hover 5 andforward-e ightmode 6i8 hasbeensimulatedand analyzed using a multizone, thin-layer Navier- Stokes solution. These anal- yses considered the clean aircraft cone guration, as well as the cone guration with external components. The V-22 employs vortex generators, strakes, and fences to en- hance aerodynamic performance. As a predesign tool, it would be desirable to use the CFD method to evaluate the effect of these de- vicesbefore thee nal evaluation on wind-tunnel or e ight tests. In the presentwork,theeffectofthemidwingfairing(alsocalledoverwing fairing) vortex generators (VGs) on the V-22 forward-e ight aerody- namicsisevaluated.TheuseofVGsisnotstraightforward,however. The effectiveness of VGs depends on how the trailing vortices are generated and used to energize the e ow inside the boundary layer. Theusermighthavetoperformalarge numberoftrial-and-errorex- periments to determine the optimum shape, incidence with respect to the oncoming e ow, and the location of the VGs before e nalizing the design applications. The use of the CFD techniques offers an excellent alternative to the required trial-and-error experiments. The present work is performed in the framework of the steady- state Navier- Stokes solution in a structured grid. A new gridding topology for embedding the VGs in an existing CFD model has been developed. The incorporation of the VGs is performed seam- lessly to allow the effect of VGs to be adequately evaluated. The VGs are not embedded using the chimera-type scheme 9 becauseof inaccuracies due to gridoverlapping and interpolations. The present work addresses the VGs installed on the midwing fairing only, and not the wing-mounted VGs nor the forebody strakes found on the engineering, manufacturing, development (EMD) cone guration of the V-22 aircraft.