Boundary layer effects on a wing in ground-effect

摘要

Purpose - The purpose of this paper is to investigate the effect a variety of different boundary layers have on a wing in ground-effect. Design/methodology/approach - Experiments were carried out in the University of Southampton's 3[variant prime]×2[variant prime] wind tunnel. A variable length splitter plate was designed and manufactured in order to generate four boundary-layer thicknesses at a selected measurement position. A single element inverted GA(W)-1 aerofoil was then introduced to the flow at varying heights above the plate. Laser Doppler anemometry (LDA) and surface static pressure measurements (both on the aerofoil surface and on the splitter plate) were recorded. Findings - The flow beneath the wing is found to be affected considerably by the presence of the boundary layer. As the boundary-layer thickness is increased, the under-wing pressure is observed to increase, hence resulting in decreased suction. Further, the LDA results indicate a modification to the wake profile. In particular, at low wing heights, the wake is observed to become entrained in the boundary layer, to differing degrees dependant on the boundary layer present and the wing height. Research limitations/implications - The acquisition of force values from the tests will have allowed further understanding of the "real world" implications of the presence of the boundary-layer thicknesses on a wing in ground-effect but this is not possible in the test facility used. Practical implications - The aerodynamics of a wing in ground-effect are of great interest for both lifting surfaces for aircraft and downforce generation in motorsport applications. The implications of this paper enhance the importance of understanding the boundary conditions present when wind tunnel testing for these applications. Originality/value - Although the influence of the boundary layer on low ground clearance objects has been well documented, the methods used here, in particular the use of the pressure tapped splitter plate and LDA, allow a further insight into the explanations behind this influence.