Question

A fast sedimenting suspension with clear supernant is known as

Answer 1

fluid if its density is greater than that of the fluid in which it is suspended. The (laminar) settling velocity of particles whose concentration is very low, that is when the flow of fluid around a particle does not affect the flow around neighboring particles, can be calculated from Stokes Law:

where D is the diameter of the particle and η is the absolute viscosity of the surrounding fluid. Δρ is the density difference between that of the particle and its surrounding fluid: if Δρ is positive the particle will settle (see Thickeners), or if it is negative the particle will float (see Flotation).