THE EFFECT OF WEIR ANGLE ON BUBBLE MOTION IN A FLOTATION FROTH - VISUAL MODELING AND VERIFICATION

A computer model of flowing foam has been developed. This provides a d ynamic, visual simulation of the motion, deformation and coalescence o f bubble between the pulp froth interface and either bursting on the s urface or overflowing the weir. The model combines the flow model of M urphy et al. [1] based on Laplace's equation and the visualisation tec hniques of Weaire and Kermode [2]. Murphy et al. [3] verified the pred iction of the flow trajectories of bubbles in a rectangular system. Th eir visualisation was based on elliptical bubbles. Here the method of Weaire and Kermode [2], developed to describe the deformation of bubbl es in a diffusing system, has been used. In addition, the model has be en extended to allow the simulation of flowing foams in systems of arb itrary dimensions.An experimental system has been developed which allo ws investigation of bubble motion and coalescence in a flowing foam wh en changing the weir angle from 30 degrees to 60 degrees. It was found that the model satisfactorily describes bubble trajectories and resid ence times. Further, the fraction of air leaving the foam as unburst b ubbles is a maximum at a specific weir angle. A coalescence criterion has been defined that determines the extent of bubble deformation requ ired to lead to coalescence and which appears to be largely independen t of system configuration. Qualitative, visual comparison of experimen tal and predicted coalescence zones show close agreement. (C) 1998 Els evier Science Ltd. All rights reserved.