chapter  5
28 Pages

Convection-diffusion problems in a moving medium

Fig. 5 .2 . Velocity components due to centrifugal and gravitational forces in a centrifuge.

scientist may be interested in the long term distribution of the pollutant over a given cross-section of the river. Our second example involves the operation of a centrifuge, which is a rotating vessel used typically to separate materials from a solvent. As the centrifuge rotates the heavier materials in the solvent are thrown onto the side walls of the centrifuge by the centrifugal force. Here a secondary radial flow is imposed on the primary rotational flow, as shown in Fig. 5.2. Many similar examples arise in sedimentation processes, such as the flow of a substance through a porous medium, for example oil in a reservoir, and the dispersal of a pollutant downwind of a tall chimney stack.