Structure of flow in hydraulic jumps

A high-speed photographic study was made of the hydraulic jump. It was found that the surface roller was made up of several vortices. These vortices are generated in the early part of the jump and travel downstream. As they move downstream, they grow by pairing. At the same time, water spills down the steepened surface to replenish the toe and subsequently is rolled up into new vortices. A Fourier analysis of the time series of the toe position indicates a cyclic mechanism, the frequencies of which appear to scale with the upstream velocity and downstream depth.