Suppression of the wing-body junction vortex by body surface suction

Abstract

A horseshoe-shaped vortex, known as a wing-body junction vortex or horseshoe vortex, forms when spanwise vorticity in the boundary layer along a surface wraps around a wing protruding from the surface. In the past, various techniques of suppressing the wing-body junction vortex have been attempted. Reported here is a novel approach whereby the oncoming wall boundary layer is removed by suction along the body surface immediately upstream of the wing. The idea is that elimination of the boundary layer essentially removes the spanwise vorticity, and inhibits the formation of a wing-body junction vortex. To test this concept experimentally, velocity data were acquired via five-hole probe surveys in a plane normal to one of the walls of a semi-infinite symmetrical airfoil. Differentiation of these data yielded mean stream wise vorticity contours and values of net circulation. In the unmodified (no suction) case, the streamwise leg of the horseshoe vortex was clearly identified. The addition of suction successfully reduced the size and circulation of the large scale vortex. In fact, at a suction volumetric flow rate of about twice that through the boundary layer, the large scale horseshoe vortex could no longer be found for our configuration. Nomenclature Q bl= boundary-layer volumetric flow rate Q s = suction volumetric flow rate Q* = nondimensional suction volumetric flow rate = QJQ H

Use of Wall Suction In Half Model Wind Tunnel Testing

“…Due to balance limitations it wasn't possible to take the half model up to stall at a Reynolds number of 1 x10 6 . The choice of Reynolds number was determined by the available full span data.…”

“…In the present experiment, locating a suction hole here was not practical for many reasons. Philips 6 demonstrated that the horseshoe vortex could be removed using increased suction upstream of the separation point. Based on Philips' 6 findings the suction system was designed to be capable of removing 1.9 times and greater of the boundary layer volume flow rate over the width of the suction hole.…”

“…The tests were done for no suction (hole taped) and with 1.36Q suction rate and at a Reynolds numbers of 0.44 x 10 6 . Fig.…”

Effects of an upstream tetrahedron on the circular cylinder–flat plate juncture flow

“…Besides, boundary-layer separation occurred at the lateral edges of the fillet. Philips et al (1992) indicated that suction applied at the upstream surface could reduce the size of the horseshoe vortex around the wingbody junction. Barberis et al (1998) attached several types of strake fillet to the wing-surface junction and observed no noticeable decrease in the vortex structure.…”

Analysis of a Three-Dimensional Corner Flow with One Rough Surface

“…The associated horseshoe vortex does not form and the stability of the flow near the junction is improved. Similarly, Philips, Cimbala and Treaster (1992) showed that eliminating the leading edge separation in the junction of a flat plate and constant thickness test surface eliminates the vortex in the downstream corner.…”