Experimental investigation on the retrograde development of hydraulic jump

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 potentially resulting in flood disasters. Hydraulic conditions and particle properties are pivotal in the hydraulic jump process. This study investigates the impact of these factors on the retrograde velocity of hydraulic jumps through experimental model tests. The retrograde movement of hydraulic jumps was captured through a high-definition camera and data acquisition system, enabling the systematic analysis of quantitative relationships between hydraulic conditions, particle properties, and retrograde velocity. The study identifies several significant factors, contributing to an increase in retrograde velocity: an elevated ratio of upstream to downstream Froude numbers, a reduction in inflow discharge, an increase in particle size, and intensified sediment supply. Furthermore, the study proposes a simple empirical formula for calculating hydraulic jump retrograde velocity, offering crucial insights into water-sand interactions in diverse water flows. These findings are indispensable for mitigating flash floods and sediment disasters in mountainous environments.