Comparison of Steady Blowing and Synthetic Jets for Aerodynamic Drag Reduction of a Simplified Vehicle

The objective of this study is to compare steady blowing and synthetic jets for drag reduction of Ahmed body. The results based on LES were validated by force measurement, static pressure coefficient and vortex shedding frequency data from experiment. Based on LES, several forcing parameters, such as jet location, jet direction, excitation velocity and driving frequency are considered. Drag reductions of 3% (using steady blowing) and 9% (using synthetic jets) are reached, respectively. Compared with steady blowing, the results of optimal parameters for synthetic jets, which were installed between the roof and rear slant, show higher drag reduction efficiency. The difference in the mechanism of flow control on Ahmed body between steady blowing and synthetic jets is studied. The excitation with a certain frequency from synthetic jets can dominate the vortex shedding process. The instability of the shear layers is suppressed to make the flow remain attached on the rear slant, so as to produce a pressure rise and drag reduction.