The hydraulic jump (‘‘shocks’’ and viscous flow in the kitchen sink)

The radial location and flow discontinuity of the hydraulic jump in a sink are discussed. The importance of viscosity in determining the location of the jump is emphasized. A model, which highlights the importance of viscous flow near the sink surface, allows us to predict the jump radius and the flow depth on the upstream and downstream sides of the jump as functions of viscosity, gravity, and flow velocity. In our approximate treatment, the jump location is independent of gravity and inversely proportional to the cube root of the viscosity.