Atwood number

== English == === Etymology === Probably named after George Atwood. === Noun === Atwood number (plural Atwood numbers) (fluid dynamics) A dimensionless number used in the study of hydrodynamic instabilities in density stratified flows: A = ρ 1 − ρ 2 ρ 1 + ρ 2 {\displaystyle \mathrm {A} ={\frac {\rho _{1}-\rho _{2}}{\rho _{1}+\rho _{2}}}} , where ρ 1 {\displaystyle \rho _{1}} is the density of the heavier fluid and ρ 2 {\displaystyle \rho _{2}} is the density of the lighter fluid. === Further reading === Atwood number on Wikipedia.Wikipedia