Flow evolution in the near field of a turbulent annular jet

Abstract

Abstract The results of an experimental study of the flow structure in the near zone of an annular swirling jet are presented. The data were obtained using a two-component laser-Doppler anemometer for the annular jets with a swirl angle of 0–60°. The results of measurements of the average velocity and pulsations in the near jet region (up to 5 diameters of the outer ring) are presented. Based on the analysis performed, it is shown that formation of an internal toroidal vortex near the nozzle plays an important role in the flow dynamics and the process of annular jet mixing. Formation of a stationary toroidal vortex outside the ring is also noted. These structures determine the flow in the near zone of the jet. With the studied Reynolds numbers, this character of the flow in the near zone leads to an increase in the mixing rate, high degree of turbulence, and an increase in the jet ejection capacity.