Experimental study on frequency characteristics of the actuations produced by plasma synthetic jet actuator and its geometric effects

The actuations generated by the plasma synthetic jet actuator (PSJA) may become weak under multiple pulses when the discharge frequency increases. In order to further study the frequency characteristics of the actuations, the high-speed Schlieren method is adopted for the experimental study on a nanosecond plasma synthetic jet actuator (NS-PSJA) made of the machinable ceramic. Three typical working states are captured by the numbers of Schlieren measurements, which are continuous, critical, and discontinuous states. For a deep understanding, the relationship between the discharge frequency and the working states of the NS-PSJA is discussed in two aspects: heat and electric charge. The critical and the saturated discharge frequencies are defined, respectively. In addition, the effects of the geometry on the frequency characteristics of the NS-PSJA are also studied such as the shape of the orifice, the electrode spacing, the depth of the cavity, and the height of the electrode. The results suggest that those geometric parameters affect the accumulation of the heat and electric charge, causing the changes of both the critical and the saturated discharge frequencies.