A Coarse-grained Transport Model of Water for Nano-fluidic Systems

Molecular Dynamics(MD) is an important tool to simulate flows at the nanoscale. The limitation of MD in simulating important biological and chemical systems having a large length and time scale increased the interest in efficient coarse-grained (CG) models. Although many existing CG models for various fluids are able to capture the structure and dynamics of the bulk fluid accurately, these models are not suited to describe transport phenomena involving explicit walls in nano-channels. Here we introduce a complete CG transport model for water in nano-channels having explicit walls. The model, which was applied to the water-graphene system, was able to demonstrate a very good match, with the structure (error<5%) and dynamical (error<1%) equilibrium properties of MD simulations. Moreover, the CG model was able to reproduce the MD results for water transport in a Poiseuille flow configuration with an error of < 5%. The accuracy of the model was transferable through different configurations and forcing conditions up to a critical force, where the MD slip velocity starts to deviate from the equilibrium prediction. Finally, the CG model was able to achieve ≈20 x speedup compared to MD simulations, making it more suitable for flows close to experimental conditions, where MD produces a poor signal to noise ratio.