Strouhal number
= Strouhal number
{c}
{title2=$St=\omega h/U$}
The Strouhal number compares the advective time $h/U$ with a prescribed forcing time $1/\omega$. Some conventions use ordinary frequency instead of angular frequency, introducing a factor $2\pi$. For a longitudinal disturbance extending over length $\lambda h$, the relevant ratio is $\lambda St$ rather than $St$ alone.