In fluid dynamics, the change from one behaviour to the other is often described by so-called critical numbers, where the transition occurs whenever this number becomes less or more than one. One of these numbers is the Froude number:

• $Fr\; \backslash equiv\; \backslash frac\{U\}\{\backslash sqrt\{gh\}\}$,

• U = velocity of the flow
• g = acceleration due to gravity (9.81 m/s² or 32.2 ft/s²)
• h = depth of flow relative to the channel bottom

If , we call the flow subcritical; if $Fr\; >\; 1$, we call the flow supercritical.

Fluid dynamics

Superkritische stroming