Active control of turbulent flow over a model vehicle for drag reduction

The objective of the present study is to reduce drag on a two-dimensional model vehicle using the distributed forcing (Kim and Choi 2002 Proc. 5th JSME-KSME Fluids Engineering Conf., 17-21 November). The forcing (blowing and suction) is applied at the upper and lower trailing edges, and is steady in time but varies sinusoidally in the spanwise direction. Both the large eddy simulation (LES) and wind-tunnel experiment are carried out. LES is performed at the Reynolds number (Re_h) of u_∞h/ν = 4200, whereas Re_h = 20 000 and 40 000 are considered in the experiment, where u_∞ is the freestream velocity and h is the height of the model vehicle. It is shown by LES that a significant base-pressure recovery (i.e. drag reduction) is obtained with the present distributed forcing, together with a substantial suppression of vortex shedding in the wake behind the model vehicle. Similar results are also obtained from the experiment at higher Reynolds numbers, indicating that the present distributed forcing for drag reduction is applicable to a two-dimensional bluff body at various Reynolds numbers.