摘要
The mixing phenomena of a two-layer density-stratified fluid induced by a jet in a tank are experimentally investigated. The upper and lower fluids are water and a NaCl-water solution, respectively, with the lower fluid issued vertically upward from a nozzle at the bottom of the tank. The jet Reynolds number Re, defined by the jet velocity and the water kinematic viscosity, ranges from 90 to 4,200. The mass concentration of the NaCl-water solution Co is less than 0.08. The flow visualization makes clear the jet behavior relative to the density interface between the upper and lower fluids. The measurement of the concentration distribution of the water paint issued with the jet highlights the effects of Re and Co on the mixing between the jet and the ambient fluid. The measurement of the fluid velocity distribution with a PIV （particle image velocimetry） system successfully elucidates the relationship between the velocity field and the resultant mixing.
