Mixing of Density-Stratified Fluid in a Cylindrical Tank by a Diagonal Jet

This study experimentally investigates the mixing of two-layer density-stratified fluid in a cylindrical tank by a diagonal jet. The upper and lower fluids are water and an aqueous solution of sodium chloride (NaCl), respectively, and the lower fluid issues from a nozzle on the tank bottom. The angle between the jet centerline and the tank bottom is 60°, and the mass concentration of the NaCl solution is 0.02. The mixing in cases that the Reynolds numbers of the jets are 713, 2319, and 3565 is investigated. The velocity fields in the central vertical cross-section are measured with a PIV (particle imaging velocimetry) system by tracing nylon particles with the diameter of 80 μm. The concentration fields in the section are visualized using Rhodamine B as the fluorescent dye. They are also measured using PLIF (planer laser induced fluorescence) from visualized images and the progresses of the mixing are evaluated quantitatively. The investigation clarifies the relationship between the mixing phenomena and the Reynolds number of the jet.