title: A Langevin model for fluctuating contact angle behaviour parametrised using molecular dynamics.
abstract: Molecular dynamics simulations are employed to develop a theoretical model to predict the fluid-solid contact angle as a function of wall-sliding speed incorporating thermal fluctuations. A liquid bridge between counter-sliding walls is studied, with liquid-vapour interface-tracking, to explore the impact of wall-sliding speed on contact angle. The behaviour of the macroscopic contact angle varies linearly over a range of capillary numbers beyond which the liquid bridge pinches off, a behaviour supported by experimental results. Nonetheless, the liquid bridge provides an ideal test case to study molecular scale thermal fluctuations, which are shown to be well described by Gaussian distributions. A Langevin model for contact angle is parametrised to incorporate the mean, fluctuation and auto-correlations over a range of sliding speeds and temperatures. The resulting equations can be used as a proxy for the fully-detailed molecular dynamics simulation allowing them to be integrated within a continuum-scale solver.
authors.affiliation: Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK. edward.smith05@imperial.ac.uk.
authors.forename: E R
authors.identifier: http://orcid.org/0000-0002-7434-5912
authors.initials: ER
authors.lastname: Smith
authors.affiliation: Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK. edward.smith05@imperial.ac.uk.
authors.forename: E A
authors.initials: EA
authors.lastname: Müller
authors.affiliation: Department of Mathematics, Imperial College London, South Kensington Campus, London SW7 2AZ, UK.
authors.forename: R V
authors.initials: RV
authors.lastname: Craster
authors.affiliation: Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK. edward.smith05@imperial.ac.uk.
authors.forename: O K
authors.initials: OK
authors.lastname: Matar