Bubble size distribution and coarsening of aqueous foams

This paper characterises the bubble size distribution of aqueous foams, produced by a compressed-air foam generator. The time evolution of bubble size distribution in aqueous foams is experimentally measured using a CCD video camera. A computer model, which predicts the change in bubble size distribution with time, is used to simulate the coarsening and disproportionation of aqueous foams. As an extension of previous computer simulations, our model incorporates the variation in liquid fraction during the foam aging process, thereby enabling the simulation of both wet and dry foams. It is found that a Weibull-type distribution best approximates the narrow bubble-size distribution produced by a compressed-air foam generator. The modelled predictions show good agreement with the experimental measurements and a sensitivity analysis indicates a significant dependence of the model on drainage (hence on the thickness of the lamellae), the Henry constant, the gas diffusivity and the surface tension of the foam solution. (C) 1999 Elsevier Science Ltd. All rights reserved.