FROUDE NUMBER (Fr)

Froude Number

The Froude number represents the ratio between inertia force and gravity force.  Froude number is expressed as:

The Froude number is applied where gravity forces are predominant.  The number is used in the analysis of:

§  Wave action.  Examples include breakwaters and ships

§  Free surface flow in open-channels

§  Hydraulic structures, such as spillways, stilling basins, weirs, and notches

§  Forces on bridge piers and offshore structures

The equation for dynamic similarity where gravity forces is predominant is given below.

EXAMPLE 1:

Flow in wide river 4.0 meters deep is to be simulated in a laboratory with a model whose channel is 1.0 meter deep. If the average speed of flow in the river is 1.0 meter per second, the speed of flow at which the model should be studied is?

Solution :

Lp = 4m            Vp = 1m/s

Lm= 1m            Vm = ?