Particle Technology

Dilute systems - sedimentation

Problems 5.7

Question 1.iv
In order to answer this question you should think about the conditions under which Stokes's equation are valid. Specifically, think about the drag around the particle.

Why should the Stokes's settling velocities of the larger particles always be greater than those found in practice (and given by the Heywood tables)?

	a) particles never actually reach their terminal settling velocity, b) Stokes only accounts for streamline or viscous drag, the Heywood Tables includes drag effects from eddies as well as viscous drag, c) particles will drag molecules of fluid with them, d) there will be convection currents.
Note, all the above may be true - you are looking for something relevant to the larger particles only.