Separation Control Characteristics of Synthetic Jets Depending on Exit Configuration

Abstract

Synthetic jets have been widely used for flow control applications and heat-transfer enhancements. A significant amount of research has been carried out on formation, evolution, and interaction of a synthetic jet under various flow conditions. This paper presents experimental and computational investigations on the characteristics of synthetic jets for different exit configurations under various flow condition. The exit configuration of a synthetic jet substantially affects the process of vortex generation and its evolution, which eventually determines the mechanism of jet momentum transport. According to the observed vortex structure, two types of exit configurations were considered; one is a conventional rectangular slot, and the other is a series of circular holes. Comparative studies were then conducted for a quiescent condition, a crossflow field, and a forced separated flow, For the quiescent condition, the velocity profiles, flow structures, and input power efficiencies of the exit configurations were examined. For the crossflow condition, interactions of synthetic jets with a freestream were studied by measuring the boundary layer profiles. For the separated flow condition, characteristics of pressure distributions and separation control capability along an inclined plate were compared. The static velocity data show the flow structure around the two exits, and the dynamic data reveal the efficacy of synthetic jets in separation control. Through various comparisons, it was observed that the exit configuration should be regarded as an important design parameter, and the circular exit provides better performance than the rectangular exit in terms of separation control and sustainable vortical structure.