An '''Archimedes number''' (not to be confused with Archimedes '''constant''', piπ), named after the ancient Greek scientist Archimedes, to determine the motion of fluids due to density differences, is a dimensionless number in the form:
:
where:
* ''g'' = gravitygravitationalacceleration (9.81 metrem/seconds²),
* ρ''l'' = density of the fluid,
* ρ = density of the body,
* μ = fluid absolute viscosity.