Sweeping Jet Actuator

When pressurized with a fluid, the sweeping jet actuator (SWJA) emits a self-induced and self-sustained temporally continuous, but spatially oscillating bi-stable jet at the outlet. The results showed that external geometric variations at the nozzle exit had a negligible impact on the oscillation frequency. However, there were notable effects on the pressure and velocity distribution in the flow field, indicating that the actuator had sensitivity towards the geometric variation of the exit nozzle—the wider the exit nozzle, the lower the downstream velocity. Notably, we observed that the mean velocity at the exit nozzle downstream for the curvature case was 40.3% higher than the reference SWJA.

Slight localized modifications of the curved sweeping jet actuator geometry can lead to a complete change in the external flow regime, making the jet velocity distribution homogeneous, similar to the angled variant of the actuator.

The jet oscillation frequency is predicted by analyzing velocity time histories at the actuator exit. A linear relationship between the jet oscillation frequency and time-averaged exit nozzle Mach number is found. We calculated the Strouhal number and founds that it is constant with the Mach number for the subsonic oscillating jet and has an average value of St = 0.0131.

The SWJ actuator reduced the separation bubble size in all cases, and the reattachment point moved upstream by 41%.

We investigated the heat transfer of a sweeping jet impinging on a flat wall and analyzed the unsteady flow structures using proper orthogonal decomposition. We observed that two distinct regions of local Nusselt number formed along the wall correlating with flow structures.