The first Froude number is the dimensionless parameter
where u is the speed of open channel flow, g is gravity, and L is the length scale.
The second Froude number is defined as the ratio of inertial force to gravitational force. It therefore applies to wave and surface behavior, and is defined by
i.e., the square of
Boussinesq Number, Gravity Wave, Internal Froude Number, Reech Number
