Entrainment in 3-D Density Currents

Density current is a dense fluid, which is continuously released from a source and spreads down a sloping surface inside a lighter , motionless fluid. Associate CFD code has been written to describe salt solution density current, which propagates three-dimensionallu in deep ambient water. The equations of continuity , momentum conservation, and diffusion are solved simultaneously in the fixed Cartesian directions, on a non-staggered grid using finite volume scheme. The velocity-pressure coupling is handled by SIMPLEC method. Comparison of the computed velocity and concentration of the density currents with the experimental data shows a good agreement between them. Analysis indicates that the dense layer spreads in all directions at a rare proportional to the entrainment coefficient. Then it approaches a normal state after release and the flow behaves as 2-Department . Depth – averaged parameters were calculated to obtain entrainment coefficient. The results showed that entrainment coefficient decreases when Richardson number increases. This result has the same trend as Ellison and Turner [1] experimental data. The present model provides a physical understanding of such complex phenomena.