Characteristics of free and submerged hydraulic jumps in different stilling basins

Abstract

A comprehensive study on free and submerged hydraulic jumps in different stilling basins was carried out. The effects of three adverse slopes, three bed roughnesses and three positive step heights on the hydraulic jump characteristics with a Froude number of 4·56–9·55 and a submergence factor of 0·1–1·5 were investigated. Two semi-theoretical solutions based on the momentum equation were developed to estimate the sequent depth ratio and the submerged depth ratio and the results were compared with experimental data. The results showed that the submerged depth ratio decreased by 22·3% compared with that of the classical jump. The lengths of the free and submerged hydraulic jumps were decreased by 47 and 32·1%, respectively, compared with the length of the classical jump. The maximum errors in the semi-theoretical estimations of the sequent depth ratio and the submerged depth ratio of free and submerged jumps were ±11% and ±16%, respectively. The thickness of the dimensionless boundary layer of the free and submerged jumps was determined to be 0·71 and 0·37, respectively. The average energy loss of the submerged jump in the conditions of this study was 10% more than that of the classical jump.