Flow Characterization and Modeling of Strong Round Synthetic Jets in Crossflow

摘要

This study focuses on the flow field of a round synthetic jet issuing into a crossflow. Six cases are investigated in which the jet-to-freestream velocity ratios range between 2.8 and 8.3. This corresponds to a medium-to-strong transverse jet, which is characterized using both two-dimensional hot-wire anemometry and particle image velocimetry techniques. A self-similar model is developed for the centerline trajectory and velocity of a transverse synthetic jet. The resulting scaling laws are validated with experimental data. The scaling coefficients are found to be independent of the synthetic jet strength (characterized by the stroke ratio) for large-velocity-ratio cases, provided that the jet velocity is calculated based on the momentum flux of the leading vortex ring of the synthetic jet. Furthermore, the velocity component parallel to the crossflow is enhanced over the crossflow velocity in the near field and fundamentally different from continuous jets. This can be explained by the induced effect of the asymmetric vortex rings in the near field, which are a result of the interaction between the crossflow and the synthetic jet.