A multiscale numerical scheme is presented for modelling nano flow systems in which length-scale separation exists, but only in one direction; for example, in long nanochannel geometries. The scheme is a hybrid atomistic/continuum method, coupling a conventional fluid model with more-costly, but accurate, molecular dynamics (MD). The hybrid approach presented here is different to the common domain-decomposition style of approach, and is more akin to distributed methods, such as the Heterogeneous Multiscale Method (HMM). In our method, the molecular dynamics solver is applied only at a few physical slices of the full macro-scale domain. The greater the scale separation, the greater the computational speed-up (when compared to a full MD simulation of the same geometry). The new method is successfully tested on a converging/diverging nanochannel case containing flow of a simple Lennard-Jones liquid. Very good agreement is found when comparing the multiscale simulation results to those of a full MD simulation.

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