Numerical Study on Flow Characteristics of Synthetic Jets with Rectangular and Circular Exits

Abstract

Flow characteristics of synthetic jets have been computationally investigated for different exit configurations under a cross flow condition. The exit configuration of a synthetic jet substantially affects the process of vortex generation and evolution, which eventually determines the mechanism of jet momentum transport. Two types of exit configurations were considered: one is a conventional rectangular exit, and the other is a series of circular holes. The interactions of synthetic jets with a free stream were performed by analyzing the vortical structure characteristics. The effectiveness of flow control was evaluated by examining the behavior of the wall shear stress. It was observed that the circular exit provides better performance than the rectangular exit in terms of sustainable vortical structure and flow control capability. In order to obtain an optimal shape of a multiple serial circular exits, comparative studies were then conducted according to hole gap and hole diameter. Detailed computations revealed that the hole gap yields a much more significant effect on flow characteristics than the hole diameter, which turned out to be relatively minor. Based on the initial strength and persistency of jet vortices, the circular exit with a suitable hole gap formed critical jet vortices that benefically affected separation control. This indicates that the flow control performance of circular exit array could be remarkably improved by applying a suitable dimensionless hole parameter