Strouhal Number

Written by Jerry Ratzlaff on . Posted in Dimensionless Numbers

Strouhal number, abbreviated as Sr, a dimensionless number, is used to describe oscillating flow.  It is used in fluid dynamics and is the ratio of inertial forces due to the unsteadiness of the flow or acceleration of inertial forces due to the changes in velocity between points in a flow field.  The representative equation and calculator are shown below.

Strouhal number formula

 $$\large{ Sr = \frac { f \; l_c } {v} }$$

Where:

$$\large{ Sr }$$ = Strouhal number

$$\large{ l_c }$$ = characteristic length

$$\large{ f }$$ = frequency of vortex shedding

$$\large{ v }$$ = velocity of flow