Main objectives : To characterize the synthetic jet generated from a circular orifice by varying the actuation frequency and the Reynolds number using particle image velocimetry (PIV) as synthetic jets have potential applications in flow control and cooling of miniature devices. Other objectives were: developing experimental facilities (wind tunnel, water tunnel, electronic cooling and blast wave attenuation) using particle image velocimetry (micro PIV in fluidic devices to Supersonic flow over objects).

What was achieved :

• The effect of different orifices diameters (15 and 25 mm) on the evolution of synthetic jet is studied using PIV, high speed flow visualizations and hot wire anemometry measurements. The reduction in orifice diameter increases the instantaneous velocity of the discrete vortices for a given actuation frequency and the cavity size.
• The effect of actuator frequencies on synthetic jet evolution has been studied. The velocity and vorticity field during formation and evolution of discrete vortex rings generated at different actuation frequencies are obtained using particle image velocimetry. The jet velocity near the orifice exit increases with increase in actuation frequencies.
• The results obtained with particle image velocimetry are verified with hotwire anemometry velocity measurements. The discrete vortices generated for lower frequencies (up to 50 Hz) travel a long distance along the downstream direction before collapsing into a turbulent structure. The vortex rings generated for higher frequencies break into a turbulent jet at a lesser distance compared to a low-frequency jet. The time history of synthetic jet velocity measured for various actuation frequencies at different axial distances using hot wire anemometry showed that the mean velocity of the jet increases with increase in actuation frequencies.
• The cooling effectiveness of synthetic jet is studied by varying the actuation frequency and the nondimensional spacing using thermal imaging camera. The temperature field obtained using a thermal imager showed that the effectiveness of synthetic jet increases with  increase in actuation frequencies.