Atwood number

Probably named after George Atwood.

Atwood number (plural Atwood numbers)

1. (fluid dynamics) A dimensionless number used in the study of hydrodynamic instabilities in density stratified flows: ${\displaystyle \mathrm {A} ={\frac {\rho _{1}-\rho _{2}}{\rho _{1}+\rho _{2}}}}$, where ${\displaystyle \rho _{1}}$ is the density of the heavier fluid and ${\displaystyle \rho _{2}}$ is the density of the lighter fluid.

• Atwood number on Wikipedia.Wikipedia