Onset and influencing factors of deflecting oscillation in planar opposed jets

• The oscillation behaviors of planar opposed jets are studied.
• Different flow regimes have been identified from experimental results.
• The impingement plane flapping flow and the onset of deflecting oscillation are reported.
• The map of the flow regimes of planar opposed jets is presented.
• Influencing factors of the deflecting oscillation are investigated.

The oscillation behaviors of planar opposed jets are experimentally and numerically studied for a Reynolds number range of 16–5000. The flow of planar opposed jets is visualized by some white smoke, and the images of smoke-seeded flow are captured by a 2-D planar particle imaging velocimetry (PIV) and a high-speed camera. Effects of the nozzle separation, the exit Reynolds number, the confinement of boundary and the width-to-height ratio of exit on the oscillation behaviors of planar opposed jets are investigated and discussed. Different flow regimes have been identified at various nozzle separations and exit Reynolds numbers. The transition from the stable separated flow to the impingement plane flapping flow and the onset of deflecting oscillation are reported for the first time from experimental results. The map describing the flow regimes of planar opposed jets is presented. Results show that the confinement of boundary and the width-to-height ratio of exit have effects on the deflecting oscillation.