The Effect Of Forward Sweep On A Wing/Body Junction

Abstract

A study has been carried out of the aerodynamic interference flow arising at the junction of a swept-forward wing, which is cambered, but without taper or twist and a flat plate on which a fully-developed, turbulent boundary layer approaches the junction. Initial CFD predictions of the pressures over the wing were carried out by the author at BAe, Hatfield. Flow visualisation tests and surface pressure measurements over the wind tunnel model were conducted at wing incidences from -3' to +9'. With the wing at 0' incidence, a single-tube yawmeter was used to explore the flow field around the leading-edge of the junction and an X-wire anemometer to examine the mean velocity and turbulence fields in the streamwise corners and at the trailing edge. The Reynolds number of the tests, based on the streamwise chord and free stream velocity of 30 m/s, was 1.03 A06. At low incidence,, a very weak separation occurred in the plate boundary layer, a very short distance upstream of the junction. However the oncoming stream converges into the junction, appearing to confine any vortical motion at the leading edge to within a very thin layer below the closest point of measurement to the plate. Rudimentary vortical flow developed slightly downstream of the leading edge, but dissipated further downstream. Although weak vortices were measured in the trailing-edge, cross-plane, these were attributed to comer separations just upstream. The turbulence activity in the streamwise corners was found to be surprisingly low, especially in the compression side of the junction. Estimates of skin-friction showed that it was lower over the majority of the trailing-edge cross-plane than in the plate boundary layer upstream of the junction. At higher incidence, flow visualisation showed that the junction region had severe stall characteristics, with 3-dimensional recirculation regions forming.