Friction Effect on Hydraulic Jump

A theoretical relationship for calculating the sequent depth ratio of the hydraulic jump formed in rectangular horizontal and roughened bed channels has been offered. This has been achieved based on considering the effect of drag force due to bed roughness in the momentum equation of hydraulic jumps. Two dimensionless parameters, dimensionless drag effect and dimensionless roughness effect are developed in order to observe the effect of roughness height on the magnitude of drag. Also, the effect of dimensionless drag effect on drag coefficient during hydraulic jump is achieved for different roughness heights at the bottom of channel. Within this study, another important physical phenomena occurring during hydraulic jumps that is the roller length as well investigated. A new model is developed for estimating the roller length in rectangular channels in terms of conjugate depths and upstream flow velocity. The developed equation has been tested for different type of rectangular cross section roughened beds as well. Keywords: Hydraulic jump, roughened bed, rectangular channel, drag force, roller length.