Published online by Cambridge University Press: 04 June 2021
The exchange of tracer mass in shallow waters between the mainstream and a recirculating flow to the side is examined in this paper over a wider range of Froude numbers than in any previous studies. We used a well-calibrated weighted essentially non-oscillatory scheme to capture the shock waves while maintaining the stability of the computation. The radiation of the waves suppressed the turbulence and the entrainment of surrounding fluids into a mixing layer. Shock waves began to form in the recirculating flow at a mainstream Froude number of $Fr_{o}\simeq 3$. The effect of the shock waves was a sudden increase in lateral mixing between the mainstream and the recirculating flow, leading to a corresponding sharp drop in a retention-time coefficient. These simulation results for the effect of the waves on mixing in shallow waters at large Froude numbers were consistent with the available data obtained from laboratory experiments.