Numerical study and modal analysis of electrode position and energy deposition amount effects on SparkJet actuator performance

This study investigates the impact of electrode positioning and the amount of energy deposited into the flow on the performance of SparkJet actuators, utilizing computational fluid dynamics (CFD) and modal analysis. The performance metric considered is impulse, defined as the time-integrated thrust. A parametric study was conducted by varying the electrode position from near the cavity bottom to more distant locations to assess the differences in impulse. In addition, the effect of three energy deposition amounts (3.11, 5.14, and 7.17 mJ) on impulse was examined. The results indicate that, for the same energy deposition amount, the impulse can vary by up to approximately 40% depending on electrode positioning. Furthermore, the impulse exhibited a general tendency to decrease as the electrode position moved closer to the orifice, regardless of the energy deposition amount. However, it showed a considerable rebound when the electrode position was near the interface between the cavity and the nozzle. To further analyze these findings, contour analysis of CFD results and modal analysis of the velocity field were conducted. The former revealed that the behavior of the low-density region inside the actuator significantly affects impulse, while the latter demonstrated that a wave with mode 0 and order 1 (an eigenfunction with a single node along the ξ direction) exerts a dominant influence on impulse. Moreover, a new variable related to this eigenfunction was proposed, enabling the prediction of impulse trends with respect to electrode position. Thus, this study successfully analyzed the previously unexplored effect of electrode positioning on SparkJet actuator performance using modal analysis, highlighting the importance of optimizing electrode position for enhanced SparkJet actuator performance.