HIPPOGRIFFE · Hybrid simulations of flow properties using atomistic – fluctuating hydrodynamics modelling for nanoconfined water

Hybrid simulations of flow properties using atomistic – fluctuating hydrodynamics modelling for nanoconfined water

The project is primarily of computational modelling character and aims to develop the universal framework of hybrid multiscale modelling methods with atomistic resolution coupled with hydrodynamics for a range of science and engineering problems which involve fluid/solid interfaces. This is as an interdisciplinary project that brings together hydrodynamics, molecular dynamics, statistical physics, applied mathematics, computational modelling, numerical methods, material science, experimental nanofluidics, and Atomic Force Microscopy (AFM) measurement technologies. To date, no existing modelling framework can address the role and behaviour of nanoconfined water in situations when the nanoscale region is an intrinsic part of the macroscopic flow, e.g. the nanoscale gap between the moving tip of the atomic microscope and the substrate or the fluid behaviour in the vicinity of a protein molecule during its diffusion in water. The main problem is that the water as a chemical substance has to be considered on atomistic and hydrodynamic levels simultaneously. The two descriptions correspond to very different scales, both spatial and temporal. On the one hand, Molecular Dynamics (MD) modelling is a mature tool for the description of dynamics of complex molecular systems at the atomic scale. On the other hand, collective motions of molecules can be described by means of statistical physics, stochastic hydrodynamics methods, e.g. based on Langevin and Landau-Lifshitz Fluctuating Hydrodynamics (FH) equations. There is still a conceptual gap in smoothly combining the two descriptions within a single multi-space-time-scale model: while the stochastic fluctuations slowly converge to macroscopic laws at the macroscopic limit they do not become atoms in the microscopic limit. Various hybrid multiscale methods have been suggested in the literature that combine adaptive resolution at the atomistic level with hydrodynamics, e.g. combining molecular dynamics with adaptive resolution coarse-grained particle methods and coupling MD with FH based on the analogy with two-phase flows, which address the problem of space-time scale interconnection with some success for liquids. However, no such adaptive resolution multiscale method currently exists for liquid-liquid/solid interface problems. The HIPPOGRIFFE project responds to challenge to develop such a method and apply it for a state-of-the art AFM experiment.

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