# Stokes-Einstein Equation

Written by Jerry Ratzlaff on . Posted in Fluid Dynamics

Stokes-Einstein equation, abbreviated as SE, is used for evaluating diffusion of spherical particles through a liquid with low Reynolds numbers.

## Stokes-Einstein Equation

 $$\large{ D = \frac{ k_b \; T }{ 6 \; \pi \; \mu \; r } }$$

### Where:

 Units English Metric $$\large{ D }$$ = diffusion coefficient $$\large{lbf}$$ $$\large{N}$$ $$\large{ k_b }$$ = Boltzmann constant $$\large{\frac{lbm-ft^2}{sec^2}}$$ $$\large{\frac{kJ}{molecule-K}}$$ $$\large{ \mu }$$ (Greek symbol mu) = dynamic viscosity $$\large{\frac{lbf-sec}{ft^2}}$$ $$\large{Pa-s}$$ $$\large{ \pi }$$ = Pi $$\large{3.141 592 653 ...}$$ $$\large{ r }$$ = radius of spherical parcticle $$\large{in}$$ $$\large{mm}$$ $$\large{ T }$$ = temperature $$\large{F}$$ $$\large{K}$$