Morton number

In fluid dynamics, the Morton number (Mo) is a dimensionless number used together with the Eötvös number or Bond number to characterize the shape of bubbles or drops moving in a surrounding fluid or continuous phase, c. The Morton number is defined as

where g is the acceleration of gravity, ${\displaystyle \mu _{c}}$ is the viscosity of the surrounding fluid, ${\displaystyle \rho _{c}}$ the density of the surrounding fluid, ${\displaystyle \Delta \rho }$ the difference in density of the phases, and ${\displaystyle \sigma }$ is the surface tension coefficient. For the case of a bubble with a negligible inner density the Morton number can be simplified to

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