Self-induced vibration of impinging synthetic jets

抄録

While numerous studies have examined self-induced vibrations in jets, the focus has predominantly been on continuous jets. Reports on self-induced vibrations in synthetic jets, which are characterized by their excited-vibration frequencies, are limited. This paper presents an experimental investigation of self-induced vibrations in two-dimensional synthetic jets interacting with a flat plate target downstream of the exit slot. Using a speaker as the synthetic-jet actuator, velocity measurements were conducted with a hot-wire anemometer, and flow visualization was achieved using the smoke-wire method and particle image velocimetry (PIV) under typical conditions. This study examined the influence of the target plate’s position and shape on the flow characteristics of synthetic jets at various dimensionless frequencies. Results were compared with those from continuous jets to discuss the conditions and mechanisms of self-induced vibration. Key findings include the occurrence of self-induced vibrations in both continuous and synthetic jets when a target plate is positioned downstream of the slot, with the vibration frequency being approximately proportional to the flow velocity and inversely proportional to the slot–plate distance; however, the frequency of self-induced vibrations is largely independent of the excitation frequency that generates the synthetic jets. The self-induced vibration frequency of the continuous jet is lower than that of the synthetic jets under identical geometric and flow-velocity conditions. Additionally, reducing the target plate thickness induces edge tone in continuous jets but suppresses self-induced vibrations in synthetic jets. This suggests that the self-induced vibrations in the synthetic jet examined in this study are not edge-tone phenomena but are more similar to the flip–flop phenomenon.