# Laplace Number

Written by Jerry Ratzlaff on . Posted in Dimensionless Numbers

Laplace number, abbreviated as La, also called Suratman number, abbreviated as Su, a dimensionless numbers, they are used in the charcaterization of free surface fluid dynamics.  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:

 Units English Metric $$\large{ La }$$ = Laplace number $$\large{dimensionless}$$ $$\large{ \rho }$$  (Greek symbol rho) = density $$\large{\frac{lbm}{ft^3}}$$ $$\large{\frac{kg}{m^3}}$$ $$\large{ l }$$ = length $$\large{ft}$$ $$\large{m}$$ $$\large{ \sigma }$$  (Greek symbol sigma) = surface tension $$\large{\frac{lbf}{ft}}$$ $$\large{\frac{N}{m}}$$ $$\large{ \eta }$$  (Greek symbol eta) = viscosity of liquid $$\large{\frac{lbf-sec}{ft^2}}$$ $$\large{Pa-s}$$