| Summary: | Jet flows have been applied in numerous fields to control flow separation. Over the last decade, several studies on the production of synthetic jets have been performed. However, little information is available about a number of aspects concerning synthetic jets, 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 on the basis of 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 the flow pattern and the 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.
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