The evolution of edge vortices underneath a diffuser equipped bluff body

The edge vortices generated by a diffuser equipped bluff body in ground effect were experimentally studied using a range of methods including particle image velocimetry (PIV), oil flow visualisation andforces. Two edge vortices were observed originating from each side of the diffuser caused by the flow separating off the side off the model and swirling underneath the model. The edge vortices were foundto enhance the downforce generated by the model as the ride height was decreased. At low values of ride height the edge vortices broke down due to the streamwise pressure gradient within the diffuser becoming too severe. This impacted on the forces such that a reduction in downforce and increase in drag was observed. The vortices were generated close the diffuser inlet, evolving from regions of weak recirculation into concentrated vortices which moved inboard and vertically up as the location moved downstream