Experimental investigation of aerodynamic flow over a bluff body in ground proximity with drag reduction devices

An experimental investigation of several drag reduction devices installed in the rear of a bluff body with square back geometry in ground proximity has been conducted. The experiments include drag, base pressure measurements and velocity measurements using particle image velocimetry (PIV). The results of the drag and base pressure measurements show that significant reductions of the total aerodynamic drag (as high as 48%) can be achieved. The results also indicated that models with base cavity have lower drag than their counterparts without it. The base pressure distributions showed a strong effect of the ground, resulting in decrease of pressure towards the lower half of the base. The devices were found to have a strong effect on the underbody flow. For the drag reduction devices a rapid upward deflection of the underbody flow in the near wake was observed. The devices were also found to reduce the turbulent intensities in the near wake region.