Experimental investigation of the retrograde development of hydraulic jumps

Hydraulic jumps frequently occur in natural river channels, impeding the movement of gravel particles within water flow. The sediment deposited in the jump region forms a sedimentary bar that moves upstream, pushing against the hydraulic jump and causing surges in upstream water levels that could potentially result in flood disasters. Hydraulic conditions and particle properties are pivotal in the hydraulic jump process. In this study, the impacts of these factors on the retrograde velocity of hydraulic jumps were investigated through experimental model tests. The retrograde movement of hydraulic jumps was captured using a high-definition camera and data acquisition system, enabling the systematic analysis of quantitative relationships between hydraulic conditions, particle properties and retrograde velocity. Several significant factors that contribute to an increase in retrograde velocity were identified: an elevated ratio of upstream to downstream Froude numbers, a reduction in inflow discharge, an increase in particle size and intensified sediment supply. A simple empirical formula for calculating hydraulic jump retrograde velocity was developed, offering crucial insights into water–sand interactions in diverse water flows. These findings are indispensable for mitigating flash floods and sediment disasters in mountainous regions.