Study on the Fundamental Flow Characteristics of Synthetic Jets (1st Report : Behavior of Free Synthetic Jets)

Abstract

Jet flows have been applied in a number of fields in order to control flow separation. Over the last decade, several studies have been carried out on the production of synthetic jets. However, there are still a large number of unknown quantities, including details of the structure and the formation mechanism of such jets. The present study attempts to clarify some of the fundamental flow characteristics of free synthetic jets, based on experiments and numerical simulations. Experimental velocity measurements and flow visualizations are performed using the hot-wire anemometer and the smoke wire method, respectively. It is found that both the temporal change in flow pattern and time-averaged velocity distribution at the centerline depend on K=ReU/S2 (the ratio of the Reynolds number to the square of the Stokes number). The unsteady downstream flow characteristics are discussed, in addition to the relation between the formative point of the synthetic jet and the value of K. Furthermore, the flow pattern and the unsteady flow characteristics of the synthetic jet are compared with those of a continuous jet.