# Strouhal number

From Encyclopedia of Mathematics

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:

$$\mathrm{Sh}=\frac{l}{vt}=\frac{\omega l}{v},$$

where $v$ is the typical velocity of the flow, $l$ is the typical linear dimension, $t$ is the typical period of time for non-stationary motion, and $\omega$ is the typical frequency (the inverse quantity $vt/l$ is sometimes also denoted by Sh).

The same criterion $H_0=vt/l$ in mechanical, thermal and electromagnetic processes is called the homochromity test.

The Strouhal number is named after V. Strouhal.

#### Comments

#### References

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

**How to Cite This Entry:**

Strouhal number.

*Encyclopedia of Mathematics.*URL: http://encyclopediaofmath.org/index.php?title=Strouhal_number&oldid=33468

This article was adapted from an original article by Material from the article "Strouhal number" in BSE-3 (originator), which appeared in Encyclopedia of Mathematics - ISBN 1402006098. See original article