Control of a Round Jet Intermittency and Transition to Turbulence by Means of an Annular Synthetic Jet

This paper deals with active control of a continuous jet issuing from a long pipe nozzle by means of a concentrically placed annular synthetic jet. The experiments in air cover regimes of laminar, transitional, and turbulent main jet flows (Reynolds number ranges 1082-5181). The velocity profiles (time-mean and fluctuation components) of unforced and forced jets were measured using hot-wire anemometry. Six flow regimes are distinguished, and their parameter map is proposed. The possibility of turbulence reduction by forcing in transitional jets is demonstrated, and the maximal effect is revealed at Re = 2555, where the ratio of the turbulence intensities of the forced and unforced jets is decreased up to 0.45.

Automated summary

This paper investigates the active control of a continuous jet by using a concentrically placed annular synthetic jet. Experiments were conducted in different flow regimes with varying Reynolds numbers, showing the possibility of turbulence reduction through forcing in transitional jets, especially at Re = 2555. The results demonstrate a significant decrease in the ratio of turbulence intensities between forced and unforced jets.