Iterative approach to weir drainage

Understanding liquid drainage in foam is an important step in determining the performance of a froth flotation system. The geometry of the flotation vessel has a major impact on drainage and thereby performance. In particular it is known that in a vessel geometry with sloping walls, a thin boundary layer of wet foam can appear near the wall, containing a high speed liquid jet that is sliding downwards. Although a zeroth order theory exists describing this liquid jet (Eur. Phys. J. E 8 (2002) 517), it has a number of unsatisfactory features which need to be rectified. The jet structure predicted does not match correctly onto the known state of the foam far from the wall. Also important physical mechanisms influencing the speed and liquid content of the jet are neglected. These problems can be corrected by iteratively improving the zeroth order solutions. The iterative approach indicates that bulk foam motion is an important effect influencing the jet boundary layer, and indeed that the foam is wetter at the wall than previously predicted.