Hydraulic Jumps and Waves at Abrupt Drops

Experimental results on the structure of the mean flow in B-jumps and waves formed at abrupt drops in open channels for a wide range of the supercritical Froude number and relative drop height are presented. In the B-jump, the supercritical stream undergoes diffusion firstly as a curved free jet sandwiched between the captive eddy on the bottom and the surface roller on the top and later as a reattached plane wall jet with the surface roller on its top. The bed shear stress in the downstream channel has been measured and well correlated along with the variation of the maximum velocity. In the wave, it has been found that the supercritical stream is deflected by the tailwater back-pressure and the deflected stream behaves like a curved surface jet till it plunges into the tailwater. The decay of the maximum velocity in the wave has been found to be generally faster than that in the classical jump and the B-jump.