Author(s): K. Konstantinidou; P. N. Papanicolaou
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Keywords: Buoyant jet; Round; Orthogonal; Linear density gradient; Calm ambient; Rise height; Horizontal spreading; Experiments; Numerical solution
Abstract: Turbulent round and orthogonal jets with rounded corners and aspect ratio 2:1, issuing into a linear density-stratified calm ambient fluid, have been investigated experimentally. The terminal height of rise and the mean elevation of the horizontal spreading have been measured in a series of experiments that extend from pure momentum jets to plumes. The data confirm the asymptotic analysis made for the two limiting flows, a jet and a plume. A round jet rose higher from an orthogonal one with the same initial kinematic characteristics. This result is congruent with earlier measurements showing that elliptical jets with a 2:1 axis ratio entrained almost twice as much (uniform) ambient fluid as the corresponding round ones. Experiments showed that the dimensionless terminal height of rise in round plumes is lower from that observed in orthogonal ones, meaning that they entrain more ambient fluid if they disperse vertically into a linear density stratification. The dimensionless rise height parameters are found to be different in jets and plumes for both types of nozzles round and orthogonal. A numerical study of the terminal height of rise of round buoyant jets showed that the entrainment coefficient measured earlier in a plume if applied to the flow can reproduce it quite accurately, while in the jet regime it has to be reduced drastically, in order to reproduce the experimental data.
Year: 2003