Research in Engineering and Aviation
Comparative Study of the Elimination of the Wing Fuselage Junction Vortex by Boundary Layer Suction and Blowing
Author(s): Johnson, M., Ravindra, K., Andres, R.M.
Volume 10 of 32nd Aerospace Sciences Meeting & Exhibit: January 10-13, 1994, Reno, NV, 32nd Aerospace Sciences Meeting & Exhibit: January 10-13, 1994, Reno, NV.
The flow over a wing fuselage junction is complex and three dimensional in nature. Due to the adverse pressure gradient created by the protruding wing, the flow separates ahead of the junction and forms a junction root vortex. Recent studies have determined that this “horseshoe” shaped vortex is formed from the fuselage boundary layer vorticity. This vortex is known to be a significant contributor to overall drag and can also
degrade the performance of downstream lifting and control surfaces as well as propulsive devices. Numerous studies have been conducted to determine the effectiveness of various methods to suppress or eliminate this vortex. An experimental investigation was conducted using a water tunnel and laser doppler anemometry system to compare two methods to suppress or eliminate the wing fuselage junction vortex. The first method involved the effective removal of the fuselage boundary layer by surface suction applied just upstream of the junction. This essentially removed the vorticity contained in the fuselage boundary layer, from which the junction root vortex is formed. The second method attempted to energize the flow by injecting high momentum fluid into the fuselage boundary layer just upstream of the junction. Velocity data was gathered for varying angle of incidence, Reynolds number, and volumetric suction and blowing rates. The data showed conclusively the reduction in strength of the vortex for various volumetric suction and blowing rates. At the highest volumetric suction rate tested, the vortex was essentially eliminated; no boundary layer can be completely removed, due to the no slip condition, and thus some boundary layer vorticity remained, from which a very weak vortex formed. At the highest volumetric blowing rate tested, a structure was formed that was actually larger than the original junction root vortex. Also, the well known bimodal characteristics of the junction root vortex structure were identified.