Downstream evolution of wingtip vortices produced from an inverted wing

Abstract

Counter-rotating vortices form from the opposite edges of lifting surfaces, and gradually move laterally and dissipate as they travel downstream (as seen in a wing-fixed reference frame). Under ground effect conditions, the vortex from a lifting wing -such as that used in an aircraft application -moves laterally outboard from the wingtip as it progresses downstream; for a downforce wing in ground effect -such as that used in an automotive application -the vortex moves laterally inboard. An interesting case is the situation where the inboard moving vortices become in close proximity to each other. The objective of the present study was to investigate counter-rotating vortices produced from a low aspect ratio downforce wing operating in ground effect. The pair of vortices move towards each other and mutually induce an upwards directed motion which in turn reduces the inboard movement driven by the ground effect. Experimental data gained from three-dimensional Laser Doppler Anemometry in a moving ground wind-tunnel was used to validate a Large Eddy Simulation computational result.

Interactions of a counter-rotating vortex pair at multiple offsets

“…As such, either Laser Doppler Anemometry (LDA) or Particle Image Velocimetry (PIV) must be used for accurate experimental results for steady vortices. However averaging point measurements can result in errors of up to 35% in tangential velocity in meandering vortex cases, emphasising the importance of a global measurement technique for meandering or unstable vortex analysis [22,23].…”