Three-dimensional Numerical Study of Submerged Hydraulic Jumps

Abstract

A hydraulic jump with strong turbulent mixing and air bubble entrainment is regarded as a transition process of a supercritical flow into a subcritical flow. In this study, the three-dimensional submerged hydraulic jumps were investigated numerically. The volume of fluid method and RSM turbulence model were used to simulate the free surface and turbulence structure. And the effects of the near-wall treatment methods including standard-wall functions, non-equilibrium wall function and enhanced-wall treatment on the flow field of the submerged hydraulic jumps were studied. Comparison between the numerical results and experimental measurements showed that the numerical model is adequate for predicting the flow pattern and free surface of the submerged hydraulic jumps. The numerical results showed that the longitudinal velocity and free surface profiles simulated by standard- and non-equilibrium wall functions are approximately similar. In the numerical simulation of the submerged hydraulic jump, the standard-wall functions were reasonably accurate in predicting the free surface, longitudinal turbulence intensity, turbulence shear stress and turbulence kinetic energy along the channel and also simulating the distribution of longitudinal velocity across the channel. The enhanced-wall treatment method despite high computational time is well able to predict the near-wall behavior of the flow such as longitudinal velocity near the channel bed and bed shear stress coefficient. Also maximum mean velocity and vertical turbulence intensity simulated by enhanced-wall treatment are more accurate than wall functions.