Dimensionless parameter that is the ratio of inertial to gravitational force. The Froude number value is one for critical flow, where the specific energy is minimum for a given depth. : The sum of the inflows to the system, used in the water-balance computation. See also BC, Q, D, S1, S2, and R.

A non-dimensional number indicating the relation between a vessel's length and its speed.

A dimensionless number that represents the ratio of inertial to gravitational fluid forces. High Froude numbers can be indicative of high flow velocity and the potential for scour.

Dimensionless parameter, the ratio of inertia to buoyancy forces

the square root of the interial-gravity force ratio; critical flow occurs at a Froude number of one, representing the minimum energy but an unstable condition, Froude numbers greater than one are rapid, and Froude numbers less than one are tranquil.

In fluid mechanics, a dimensionless parameter expressing the ratio of nonlinear advection to the pressure gradient acceleration associated with the variation of fluid depth, i.e. of the fluid speed to a measure of the internal wave speed. It is defined by where is the flow velocity, g the gravitational acceleration, and the fluid depth, and the approximate phase speed of shallow water gravity waves. A Froude number greater than unity is indicative of what is called supercritical flow, and one less than unity of subcritical flow. When dealing with internal waves, an internal or densimetric Froude number is defined which corresponds to the ordinary Froude number with with the reduced gravity ' replacing in the above. See Turner (1973) and Houze (1993).

Used in hydraulics as an analog to the Reynolds number. It is the ratio of inertial forces to gravitational forces.

The Froude number is a dimensionless number used to quantify the resistance of an object moving through water, and compare objects of different sizes. Named after William Froude, the Froude number is based on the speed/length ratio discovered by Froude, and on which the Froude number is based.