Experimental study of the air–water shear flow in a hydraulic jump

Although the hydraulic jump has been investigated experimentally for nearly two centuries, little information is known of the air–water flow properties in the shear region. New experiments were performed in a horizontal channel with partially-developed inflow conditions. Distributions of air concentration, mean air–water velocity and bubble frequency were recorded and presented herein. The results indicate an advective diffusion of air in the shear layer. The velocity profiles have a similar shape as wall jet flows but different quantitative parameters must be introduced. The relationship between air content and bubble frequency has a parabolic shape which is not yet understood but was observed previously in open channel flows.