# Settling velocity (Stokes law)

## Description

Stokes’ law can be used to calculate the viscosity of a fluid. Stokes’ law is also important in the study for Viscous Drag , Terminal Velocity even in Fluid Flow.

The terminal velocity of a particle which is falling in the viscous fluid under its own weight due to gravity, is depended on the radius of the spherical particle, the mass density of the sphere and the fluid and the dynamic viscosity of the fluid.

Stokes’ law can be used to calculate the size of a settling basin needed in order to remove a desired particle size. Stokes’ law gives a settling velocity determining an effective settling basin depth; so solids removal depends upon effective settling basin surface area, while the depth component of settling basin volume remains important for storage of settled solids.

Related formulas## Variables

U_{s} | Settling velocity (m/s) |

ρ_{p} | Density of particle (kg/m^{3}) |

ρ_{m} | Density of medium (kg/m^{3}) |

g | Standard gravity |

r | Particle radius (m) |

μ | Viscosity of medium (kg/(m*sec)) |