Detergent Foam Images as Analogue/Digital Model Fluids. 1. Phase Behavior and Effective Pair Potentials

Abstract

Detergent foam images are investigated as analogue/digital (A/D) models for simple fluids. Results of foam preparation/image processing experiments with quasi-two-dimensional systems are illustrated. In the analysis, the pair and triplet correlation functions, g(r) and ξ(ϑ,s;r), are measured for the vertexes of plateau border networks. The phase morphology is characterized by the amplitude and extent of oscillations in g(r). Effective pair potentials u(r) are calculated via the lowest order equation in the Born−Yvon−Green hierarchy. The u(r) are further investigated via Monte Carlo calculations and the Morse function. The experimental data are used to calculate the pair correlation entropy and the compressibility factor as functions of particle number density. These and other observables enable comparisons between the model systems and real atomic fluids. Overall, the results show foam images to mimic fluid structure at the atomic level in several respects. For the experimental conditions discussed, succe...