AN EXPERIMENTAL AND NUMERICAL STUDY OF SUBMERGED HYDRAULIC JUMPS FORMING AT LOW-HEAD DAMS

摘要

This study, which includes both experimental and numerical modelling results, investigates the potentially dangerous conditions that can occur when low-head dams (or 'weirs') are overtopped and submerged-type hydraulic jumps form in the immediate downstream channel. The combination of high local turbulence levels, air entrainment, and strong surface currents associated with submerged jumps (also known as submerged 'rollers') can pose a significant risk to swimmer and boater safety. In this study, the conditions governing the formation of submerged jumps, as well as their dynamic characteristics, are investigated for a wide range of flows and different boundary conditions. The research seeks to establish improved guidelines for the design and safe operation of low-head dams. The experimental phase of the study involved physical model tests to determine: (i) the hydraulic conditions that govern the submerged jump formation, and (ii) the dynamic characteristics of the surface roller (vortex). The numerical modelling work used 'interFoam', which is an Eulerian 3D solver, included in the OpenFOAM toolbox, for multiphase incompressible fluids that features the Volume of Fluid approach (VOF) to capture the air-water interface. The numerical model developed in this study was subsequently validated with the experimental data. The analysis conducted on the time-history of the kinetic energy production sheds new light on the mechanism of formation of submerged hydraulic jumps and their dynamic characteristics.