A dimensionless number used in momentum transfer in general and buoyancy, fluidization, and motion due to density difference calculations in particular. Proportional to (Gravitational force) / (Viscous force).

Ar = (g rhos L3) (rhos - rhof) / (mu2)

g: gravitational acceleration, L: characteristic length, mu: viscosity, rhof: fluid density, rhos: solid density


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