NUMERICAL STUDY ON THE CHARACTERISTICS OF VORTEX FREQUENCY AND LAMINAR MIXING OF A PASSIVE SCALAR IN COAXIAL JET FLOWS

동축제트의 와류주파수 및 혼합특성에 대한 수치해석 연구

This study focuses on the near-field vortical structure and dynamics of coaxial jets. The characteristics of laminar flow and mixing in coaxial jets are investigated using a unsteady flow simulation. In order to analyze the geometic effects on the vortical structure, several cases of different configurations are selected for various values of the velocity ratio of inner jet to outer jet. From the result, it is confirmed that mixing is promoted by the development of vortical structure and the interaction between inner jet and outer jet. This feature is strongly related to the vortex frequency in the shear-layers. The vortex frequency depends on the velocity ratio and the lip thickness of inner nozzle, but the outer pipe length has no effect on the frequency variation.