Multi-scale modelling and hybrid atomistic-continuum simulation of non-isothermal flows in microchannels

Abstract

A hybrid atomistic-continuum method devoted to the study of multi-scale problems is presented. The simulation domain is decomposed into three regions: the bulk where the continuous Navier-Stokes and energy equations are solved, the neighbourhood of the wall simulated by the Molecular Dynamics and the overlap region which connects the macroscopic variables (velocity and temperature) between the former two regions. For the simulation of long micro/nano-channels, we adopt multiple molecular blocks along the flow direction, what enables the accurate capture of the velocity and temperature variations from the inlet to the outlet. The validity of the hybrid method is shown by comparisons with both analytical solutions and Finite Volume simulations. This method is then applied successfully to the study the hydrodynamic and thermal development of a liquid flow in a long micro/nano-channel.

Hybrid atomistic-continuum multiscale method for fluid flow with density variation in microchannels

“…where φ denotes an averaged value of the variable φ and φ (z) refers to the variation of φ with respect to the zordinate (Vu et al, 2016 …”

“…This paper aims to extend the hybrid atomistic-continuum multiscale method developed by Vu et al (2016) to study the gas flow problems in long microchannels involving density variations.…”

“…To enhance the description of the fluid flow in channels with a large aspect ratio, a hybrid numerical model coupling an atomistic approach and a continuum model have been recently developed to take into account the multiscale behaviour of the transfer phenomena (Vu et al , 2016). The molecular dynamics simulation method is used in molecular blocks distributed along the channel wall, and a finite-volume discretization is adopted in the flow bulk to solve the macroscopic transfer equations in the axial direction of the channel.…”

“…In this way the large aspect ratio micro and nano channels can be simulated (Vu et al, 2016); the information transfer from microscopic elds to continuous eld is done by interpolations between the micro simulations. This approach keeps the benets of domain decomposition method, i.e.…”

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Purpose This paper aims to extend the hybrid atomistic-continuum multiscale method developed by Vu et al (2016) to study the gas flow problems in long microchannels involving density variations.

Design/methodology/approach The simulation domain is decomposed into three regions: the bulk where the continuous Navier–Stokes and energy equations are solved, the neighbourhood of the wall simulated by molecular dynamics and the overlap region which connects the macroscopic variables (density, velocity and temperature) between the two former regions. For the simulation of long micro/nanochannels, a strategy with multiple molecular blocks all along the fluid/solid interface is adopted to capture accurately the macroscopic velocity and temperature variations.

Findings The validity of the hybrid method is shown by comparisons with a simplified analytical model in the molecular region.

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