# Rossby Number

Written by Jerry Ratzlaff on . Posted in Dimensionless Numbers

Rossby number, abbreviated as Ro, is a dimensionless number that is used in describing fluid flow. It is the ratio of internal to Coriolis force.  It is usd to characterise the importance of Coriolis accelerations due to planetary rotation.  The equation and method of calculation is shown below.

## formulas that use Rossby number

 $$\large{ Ro = \frac{ U }{ l_c \; f} }$$

### Where:

$$\large{ Ro }$$ = Rossby number

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

$$\large{ U }$$ = characteristic velocity

$$\large{ f }$$ = Coriolis frequency