Stokes' law


Stokes’ law is an expression for the frictional force – also called drag force – exerted on spherical objects with very small Reynolds numbers (e.g., very small particles) in a continuous viscous fluid. Stokes’ law makes the following assumptions for the behavior of a particle in a fluid: – Laminar Flow – Spherical particles – Homogeneous (uniform in composition) material – Smooth surfaces – Particles do not interfere with each other.
The force of viscosity on a small sphere moving through a viscous fluid (acting on the interface between the fluid and the particle) is depended on the radius of the spherical object, the particle’s velocity and the dynamic viscosity.

Related formulas


Fdfrictional force - or "Stokes' drag" - acting on the interface between the fluid and the particle (N)
μdynamic viscosity (N*s/m2)
Rradius of the spherical object (m)
vparticle's velocity (m/s)