Correlation between drag variation and rear surface pressure of an Ahmed body

The correlation between drag variation and rear surface pressure of an Ahmed body with a slant angle of 25° is experimentally studied. The body is forced with several independent steady blowings deployed around the rear window and the vertical base. Several combinations of the independent blowings are investigated, which produce a drag reduction of 16–26%. It is found that the drag or total pressure variation associated with each combination of blowings could always be reasonably well represented by two local pressures, one on the rear window and the other on the base, and the correlation between this drag and a linear combination of the variations in the two local pressures is approximately linear. Extensive flow measurements are conducted to understand the flow physics behind the finding, which provides a valuable guidance on the choice of the feedback pressure signals for future closed-loop drag reduction control studies. Graphic abstract