Dilution of Buoyant Two-Dimensional Surface Discharges

The flow of heated water from an open channel into a reservoir containing colder and essentially stagnant water has been studied in a laboratory flume. The basic mechanisms which produce mixing between heated discharge and cold water at the transition from a shallow to a deep channel have been documented. Experimental data on internal wave formation and on mixing involving various kinds of internal hydraulic jumps are presented in dimensionless form. A typical example showing the distribution of eddy diffusivities in the presence of a temperature gradient illustrates the mixing process outside the immediate outlet area. The information obtained supports the speculation that dilution of thermal plumes in many prototype situations must be produced mainly by horizontal mixing.