Modelling and prediction of foam structure

Abstract

The primary objective of this thesis is to explore the relationship between the surface and underlying structure of dry foams. This relationship is important for both research and industry because the surface film size distribution is typically the only information available in opaque foams when referring to the underlying bubble size distribution. This study is carried out by simulating foams with free surfaces. Firstly, the method of simulating 3D dry foams with free surfaces is presented. The simulation method is verified for foams with uniform bubble sizes by comparing their simulation results to experimental values reported in literature. The validity of the method and its ability to accurately model the structure of both surface and internal bubbles is demonstrated by the excellent agreement between the experimental study and the simulation results. Secondly, the simulation results are shown for the relationship between the surface film size distribution and the surface bubble size distribution. The results show that, for a given surface bubble size, there is a distribution of possible surface film sizes. However, for the range of polydispersity used in this thesis, the distribution of the ratio of film size to the size of bubble to which it is attached is found to be independent of the underlying bubble size distribution. A functional form of this relationship is obtained by nonlinear regression. Based on the functions obtained, the surface film size distributions can be computed using the underlying surface bubble size distribution. This is the inverse of what is acquired and therefore a numerical procedure for obtaining the surface bubble size distributions using the corresponding surface film size distribution is developed. This method is demonstrated to accurately reproduce the results from the full structural foam simulations