Froude Number

Introduction to the Froude Number

The Froude Number is a dimensionless parameter measuring the ratio of the inertia force on a element of fluid - to the weight of the fluid element, the inertial force divided by gravitational force.

The Froude Number can be expressed as

Fr = v / (g l)1/2                       (1)


Fr = Froude number

v = velocity (m/s)

g = acceleration of gravity  (9.81 m/s2)

l = characteristic length  (m)

The Froude Number is relevant in fluid dynamic problems where the weight of the fluid is an important force.

In general this is the situation for free surfaces like cold windows and hot radiators. It is used when calculating momentum transfer in general and open channel flow and wave and surface behavior in particular.

The Froude Number is also important in analyzing flow in spillways, weirs, channel flows, rivers and in ship design.

Related Topics

  • Fluid Mechanics - The study of fluids - liquids and gases. Involves velocity, pressure, density and temperature as functions of space and time

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