Sedimentation and Free settling

Sedimentation or free settling refers to the sinking of solid particles in a volume of liquid which is large with respect to the total volume of particles, hence particle crowding is a neg-Hgible phenomena. Usually, free setthng predominates when the mass fraction of solids is less than 15 wt.%. [Pg.1109]

Consider a spherical particle of outside diameter, d, in m and density in kg.m falling under the acceleration of gravity in m.s in a viscous fluid of density under free settling conditions, i.e., ideally in a fluid of infinite extent. The particle is acted upon by three forces [Pg.1109]

According to Stokes (1891) the drag force on a spherical particle is entirely due to viscous resistance and is described by following the equation [Pg.1109]

Therefore the terminal settling velocity of the solid particles is given by the two relations [Pg.1109]

Stokes law is valid for particles below about 50 pm in diameter. The upper size limit is determined by the dimensionless Reynolds number, while Newton s law holds for particles larger than about 0.5 cm in diameter. There is therefore an intermediate range of particle size in which neither law fits experimental data. [Pg.1109]

Big Chemical Encyclopedia