Investigation of the Effect of Outlet Structures on the Jet Flow Characteristics in the Circulating Jet Tank

A revised numerical model of circulating jet tank (CJT) was constructed by adding four momentum sources. The radial distribution tendency of total pressure predicted by large eddy simulation had a good agreement with experimental results. The axial velocities at the center of downcomers have parabolic attenuation tendency with the increasing axial positions. The inductive and restrictive effects of outlets on the jet flow performances were evaluated by the parameters, such as jet velocity decay, spreading rate and energy dissipation. The optimum factor of outlet structures was proposed based on the ratio of spreading rate to energy dissipation. Numerical results show that the downcomers equipped with four symmetrical rectangular outlets contribute more to reduce the decay of jet centerline velocity and make good use of the entrainment between the jet and bulk liquid to generate the largest spreading rate. Furthermore, a nearly plug flow pattern and the maximum value of optimum factor are attained compared with other types of outlets. The optimum factors of rectangular outlets firstly increase then decrease with the increasing ratios of width to diameter of the downcomers. Rectangular outlets induce the jet to expand and get the largest dimensionless jet length and spreading rate when the ratios of width to diameter w/D-1 approach 0.08.