Ekman number
= Ekman number
{c}
{title2=$E=\nu/(2\Omega L^2)$}
{wiki}
The ratio of viscous force to <Coriolis force> in a rotating fluid at length scale $L$. This convention uses rotation frequency $2\Omega$; conventions omitting the factor two are also common. For small $E$, bulk viscosity is weak but no-slip boundaries can form <Ekman layers> of thickness of order $L\sqrt E$, with relatively larger boundary shear stress.