## Stokes number, $$St$$

https://doi.org/10.1351/goldbook.S06029
Sometimes referred to as the inertial parameter; it is an index of the impactability of an @[email protected] particle. It is defined by the equation: $$St = 2\ \tau \ (V_{\text{t}}- \nu_{\text{t}})\ D_{\text{p}}$$ where $$D_{\text{p}}$$ is the diameter of a small drop, $$V_{\text{t}}- \nu_{\text{t}}$$ is the difference in fall velocities of the drop and @[email protected] particles and $$\tau$$ is the characteristic @[email protected] of a particle.
Source:
PAC, 1990, 62, 2167. (Glossary of atmospheric chemistry terms (Recommendations 1990)) on page 2216 [Terms] [Paper]