Upstream propagation of surges and bores: free-surface observations

In a free-surface flow, a sudden increase in water depth induces a positive surge, also called compression wave or bore. Herein a physical study was conducted in relatively large-size rectangular channel with a smooth bed. The upstream propagation of breaking and undular bores were investigated with a broad range of Froude numbers Fr ranging from 1.1 to 2.3. Both instantaneous and ensemble-averaged free-surface measurements were performed nonintrusively. The observations showed the occurrence of undular bores for 1 1.4 to 1.5, and breaking bores with secondary waves for 1.2-1.3 10