Numerical simulation of free and submerged hydraulic jump over trapezoidal and triangular macroroughness

Abstract

Hydraulic jump is a phenomenon that occurs in open channel flow and has wide utility in hydraulic engineering. The present study considered macroroughness features in the bed to improve the characteristics of free and submerged hydraulic jumps. For that, the most often utilized triangular macroroughness elements are contrasted with a distinctive trapezoidal macroroughness. This study implied a numerical model based on computational fluid dynamics (CFD) to investigate the hydraulic jump characteristics over the macroroughness and represented the important features of hydraulic jump such as sequent depth ratio, tail-water depth ratio, longitudinal velocity profile, flow pattern of velocity vector, and contours for turbulent kinetic energy over smooth and macrorough beds. It is seen that for a specific Froude number, triangular macroroughness outperforms trapezoidal macroroughness. The average value of the length of the roller for trapezoidal and triangular macroroughness is found to be 23 % and 46.06 % shorter than the smooth bed in the case of a free jump, whereas 17.85 % and 36.33 % shorter than the smooth bed in the case of a submerged jump, respectively. To check the accuracy of the numerical model, the basic parameters of a hydraulic jump, such as sequent depth and tail-water depth ratio, are compared with the experimental findings of the present work, and the mean error between the CFD and experimental models is reported to be within 6 %, which confirms the reliability of the CFD model and can be applied to real hydraulic engineering.