抄録
A development process of a low-density jet, such as a helium gas and a hot air jets, is different from that of a constant-density jet. Side jets, which are radial ejections, are formed at vicinity of the nozzle exit and mixing of fluids between the jet and the surroundings is enhanced. Helium gas jets were discharged from a round nozzle upward and visualized by planar laser Mie scattering (PLMS). A configuration of the side jets varies with Reynolds number. Side jets at low Reynolds number are similar to a bifurcation. A flow structure of the side jets at low Reynolds number was mainly investigated. The visualized side jet was recorded using a high-speed video camera. The velocity field involving the side jet was visualized by PIV. The instantaneous velocity in the potential core was measured by a hot-film anemometer. The velocity in the potential core periodically fluctuates, and lamps with high speed and low speed are alternately passing the inside of the potential core. The potential core is pulsating radially, and the side jets at the low Reynolds number is generated periodically.
