# Laplace Number

Written by Jerry Ratzlaff on . Posted in Dimensionless Numbers

Laplace number, which is also called Suratman number.  Both are dimensionless numbers and are used in the charcaterization of free surface fluid dynamics.  The Laplace number and Suratman number is abbreviated as La and Su, respectively. It is a ratio of surface tension to the momentum transport inside a fluid.

### Laplace Number Formula

$$\large{ La = \frac { \sigma \rho l } { \eta^2 } }$$

Where:

$$\large{ La }$$ = Laplace number

$$\large{ \rho }$$  (Greek symbol rho) = density

$$\large{ l }$$ = length

$$\large{ \sigma }$$  (Greek symbol sigma) = surface tension

$$\large{ \eta }$$  (Greek symbol eta) = viscosity of the liquid

Tags: Equations for Fluid