The double surge wave generated by a supercritical flow entering upstream of a pre-existing current

Abstract

The paper discusses a particular phenomenon that develops in an open channel flow when a supercritical current enters from upstream a pre-existing current. In this case, a system of two surge waves, which propagate downstream while distancing each other, develops; the two surges can be either positive or negative, as well as shock or diffuse waves, and arrange into four different configurations. A model of the double surge wave system that allows to estimate the waves characteristics such as the height and the speed of the wave fronts, is described and discussed, and a criterion to predict the wave configuration is proposed. The model is then tested against the results of lab experiments that confirmed its reliability. Some numerical simulations are also performed to describe and further discuss the double surge wave system that develops under different conditions of practical interest.