Active Flow Control of the 3D Separation on a Ahmed Body Using Steady Microjet Arrays

A model of a generic vehicle shape, the Ahmed body with a slant angle of 25°, is equipped with an array of blowing steady microjets 6mm downstream of the separation line between the roof and the slanted rear window. The goal of the present study is to evaluate the effectiveness of this actuation method in reducing the aerodynamic drag, by reducing or suppressing the 3D closed separation bubble located on the slanted surface. The efficiency of this control approach is quantified with the help of aerodynamic load measurements. The changes in the flow field when control is applied are examined using PIV measurements and skin friction visualizations. By activating the steady microjet array, the drag coefficient was reduced by 9 to 11%, depending on the Reynolds number. The modification of the flow topology under progressive flow control is particularly studied.