A model system for understanding coalescence and its consequence on gas-liquid flows – CoLiFlow

We wish to use model systems, mixtures of miscible liquids, to study quantitatively the link between coalescence and the behaviour of two-phase gas-liquid flows. We have recently shown that films of liquid mixtures are stabilised by a surface elasticity effect that is fully described by the thermodynamics of mixtures, and that can be fully controlled experimentally. We propose to carry out various experiments at scales ranging from the single film to the macroscopic gas-liquid flow, and to couple them to numerical resolutions in order to understand the mechanisms at play during the coalescence of a liquid film, a surface bubble, an air sheet and a foam formed in a mixture of liquids. These results will be linked quantitatively to the different regimes observed when a gas is injected into a mixture. Our project will enable us to understand and describe coalescence phenomena in the presence of surface elasticity, as well as the effect of physico-chemical parameters on two-phase flows. This understanding is essential in many applications where controlling the formation of foams in flowing liquids is crucial, either during manufacturing or transport processes - depressurisation, entrainment of air during mixing, etc. - or in the conditions of use of certain liquids, such as lubricants, where the appearance of bubbles has an impact on efficiency.