Strouhal number

A criterion for the similarity of non-stationary motions of liquids or gases. The Strouhal number characterizes the identity of the flow of the processes in the course of time:

where is the typical velocity of the flow, is the typical linear dimension, is the typical period of time for non-stationary motion, and is the typical frequency (the inverse quantity is sometimes also denoted by Sh).

The same criterion in mechanical, thermal and electromagnetic processes is called the homochromity test.

The Strouhal number is named after V. Strouhal.

References

[a1]	L.I. Sedov, "Similarity and dimensional methods in mechanics" , Acad. Press (1959) (Translated from Russian)