Abstract
A negatively-buoyant jet discharged horizontally into an ambient fluid at res in a large rectangular water tank has been investigated numerically using a non-isotropic Smagorinskii model of the large eddy simulation (LES). The turbulent jet discharged continuously out of a straight horizontal nozzle with a square cross-section spreads so that it mixes with the surrounding fluid and gradually sinks down as it moves forward. The purpose of this work is to clarify the dynamical structure of such a spreading jet consisting of a heavier fluid numerically. The analysis has been carried out for two cases of the ambient fluid : (1) homogeneous, and (2) stably stratified. The validity of the present numerical method for analyzing the negatively-buoyant turbulent jet is first confirmed by comparing a numerical result for the case (1) with the experimental one by Davies and Ahmed9) . In case (2), the paths as well as forms of the jet and the velocity distributions in the spreading jet are found at different values of a parameter (1m /h) depending on the initial velocity and density of a discharged jet. The analysis shows that an initially negatively-buoyant jet can take a complicated path as it becomes neutrally-buoyant by entraining the surrounding fluid. The effects of the background density gradient on the jet forms are also clarified when 1M/h is constant.
