Laplace number

The Laplace number (La), also known as the Suratman number (Su), is a dimensionless number used in the characterization of free surface fluid dynamics. It represents a ratio of surface tension to the momentum-transport (especially dissipation) inside a fluid.

It is defined as follows:

$La = Su = \frac{\sigma \rho L}{\mu^2}\,$

where:

• σ = surface tension
• ρ = density
• L = length
• μ = liquid viscosity

Laplace number is related to Reynolds number (Re) and Weber number (We) in the following way:

$La = \frac{Re^2}{We}\,$

See also

• Ohnesorge number - There is an inverse relationship, La = Oh ^{− 2}, between the Laplace number and the Ohnesorge number.