Three-dimensional computation of buoyant plumes

Abstract

The flow field resulting from the interaction of a stream with the much larger body of flowing water into which it debouches was analyzed. Local density of the water was expressed as a function of salinity and/or temperature. Three-dimensional unsteady conservation equations used to describe the interaction included the effects of buoyancy, inertia, and the difference in the hydrostatic heads of the two currents. Turbulence effects were modeled by using an effective eddy viscosity. For cases of interest, boundary conditions were essentially constant for the time required for the plume to converge to steady state. The conservation equations were solved with a time-dependent finite difference technique that continuously adjusted the flow field variables until a steady flow resulted. A sample case from a simulation of the South Pass of the Mississippi River revealed three-dimensional flow in the interaction region. Buoyancy near the river mouth induced a pair of standing vortices. Farther away from the mouth a strong crosscurrent dominated the flow. Numerical results agreed qualitatively with available field data.