Stokes number calculator

Back to Utilities

The Stokes number compares a particle's inertial response time to a characteristic time of the surrounding flow. It is defined as

St = τ_p / τ_f, with the particle relaxation time (Stokes-drag regime) τ_p = ρ_p d_p² / (18 μ) and the flow time scale τ_f = L_c / U, built from a characteristic length L_c and velocity U.

Particle diameterd_p [m]

Particle densityρ_p [kg/m³]

Dynamic viscosityμ [Pa·s]

Characteristic velocityU [m/s]

Characteristic lengthL_c [m]

–

s

Particle relaxation time τ_p

–

s

Flow time scale τ_f

–

–

Stokes number St