This paper presents a numerical unsteady analysis of a SJA impact on a car wake flow. First, for the optimal reduced frequency F+, the influence of the Cμ on the mean aerodynamic drag reduction 〈Cd〉 is observed. A spectral analysis of the vortex shedding coming from the upper and the lower part of the car and of the drag coefficient is then presented for different Cμ values. Preliminary results suggest that maximum drag reduction is obtained when most energy in the wake comes from the actuator forcing frequency rather than the natural vortex shedding frequencies of the two contributions. This work is completed by a phase locked analysis of the synthetic jet actuator local effect on the turbulent boundary layer just before the flow separation. For the fixed optimal F+, different Cμ values are compared. The streamwise velocity profiles seem to show that maximal efficiency of the control is obtained when the synthetic jet injected momentum is introduced in the logarithmic sub-layer part of the turbulent boundary layer.
Scalings for rectangular synthetic jet trajectory in a turbulent boundary layer
