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:

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

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:

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

See also

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