Hydraulic jump

The hydraulic jump (including water jump or hydraulic jump) is a term from the Hydromechanics open flume. There is an abrupt change of flow very fast to very slow running water. Although the reverse case is also a change of flow (see below ), but is continuous. These phenomena occur in open channel flow.

Explanation

If the discharge in a channel is slower than the speed of propagation of disturbances (waves), then this is referred to as streaming or subcritical effluent ().

If the discharge is faster than the speed of propagation of faults, then this is referred to as shooting or over -critical outflow ().

Is used to distinguish the Froude number

With

• V = mean velocity,
• G = acceleration of gravity,
• H = water depth.

A hydraulic jump (hydraulic jump) occurs when flow transition from shooting to the flowing runoff:

• Transition is abrupt ( discontinuous)
• Substantial losses while placing Shooting from the upper water in the underwater
• Water depth is greater than the water boundary
• Speed ​​is lower than the speed limit
• At schießendem inflow with Fr < 1.7 done a Undulating or wavy hydraulic jump

A second type of flow transition (no hydraulic jump ) is produced by the flowing for shooting Drain:

• Requirement is the Gerin Nine continuity
• Change in water depth is continuously
• Speed ​​is greater than the speed limit

A hydraulic jump is, for example, water roller.

An analogous phenomenon are shock waves in gas flows. The Froude number in channel flow corresponds to the Mach number in gases.

Furthermore, the mechanism of energy conversion in the hydraulic jump is similar to that in the breaking of waves surf related.