Numerical investigation on synthetic jet control for flow over two-dimensional square cylinder

Flow around a square cylinder with synthetic jet located at the cylinder's rear surface is investigated numerically. The numerical analysis is carried out at low Reynolds number of 100 with the excitation frequency normalized by the natural vortex-shedding frequency f_e/f₀ varying from 1 to 6 and the peak velocity normalized by the free-stream velocity U_e/U_∞ varying from 1 to 5. It is found that drag reduction can be achieved by applying synthetic jet control, and a maximum drag reduction rate of about 29.2% is obtained for the case of U_e/U_∞ = 5 and f_e/f₀ = 3. For the wake vortex structures under present synthetic jet control, four typical patterns, named as no-effect mode, alternative shedding mode with half frequency lock-in, asymmetric shedding mode of unilateral deflection and symmetric shedding mode, are observed.