Flow Structures in the Initial Region of a Round Jet with Azimuthally Deformed Vortex Rings Utilizing a Sound Wave

Vortex ring is formed and breaks down through wavy deformation in the initial region of a round jet. We attempted to deform a vortex ring of the round jet azimuthally and wavily using synthetic jets. The synthetic jets are generated at the side of a round nozzle by a sound wave. From flow visualization of the excited jet, it is found that the vortex ring is azimuthally and wavily deformed by the synthetic jets and the deformed shape is determined by the number of synthetic jets. Outflows from the jet column appear between the synthetic jets. From the results by a PIV, the velocity and pressure of outflows are large and low. The velocity in the jet column is fluctuated largely and periodically. The separated flow formed by the synthetic jets are similar to the side jets in a helium gas jet.