Hybrid molecular dynamics-continuum simulation for nano/mesoscale channel flows

Abstract

The present study deals with multiscale simulation of the fluid flows in nano/mesoscale channels. A hybrid molecular dynamics (MD)-continuum simulation with the principle of crude constrained Lagrangian dynamics for data exchange between continuum and MD regions is performed to resolve the Couette and Poiseuille flows. Unlike the smaller channel heights, H < 50r (r is the molecular length scale, r % 0.34 nm for liquid Ar), considered in the previous works, this study deals with nano/mesoscale channels with height falling into the range of 44r £ H £ 400r, i.e., O(10)-O(10 2 ) nm. The major concerns are: (1) to alleviate statistic fluctuations so as to improve convergence characteristics of the hybrid simulation-a novel treatment for evaluation of force exerted on individual particle is proposed and its effectiveness is demonstrated; (2) to explore the appropriate sizes of the pure MD region and the overlap region for hybrid MDcontinuum simulations-the results disclosed that, the pure MD region of at least 12r and the overlap region of the height 10r have to be used in this class of hybrid MDcontinuum simulations; and (3) to investigate the influences of channel height on the predictions of the flow field and the slip length-a slip length correlation is formulated and the effects of channel size on the flow field and the slip length are discussed.

Dependence of nanoconfined liquid behavior on boundary and bulk factors

“…In this paper, p = 100, i.e., pδt P = δt C . An extra depressing force f d is exerted on the molecules in the C-P layer to prevent molecules from drifting away [33,34]:…”

Molecular dynamics-based prediction of boundary slip of fluids in nanochannels

“…The spatial coupling between continuum equations and molecular dynamics was achieved through constrained dynamics in an overlap region, which successfully simulated sudden-start Couette flow and channel flow with nano-scale rough walls. Subsequently, Yen et al (2007) performed hybrid molecular dynamics-continuum simulation for nano/mesoscale channel flows, and proposed a novel treatment of force evaluation in hybrid data exchange between MD and continuum regions. It was demonstrated that the modified scheme proposed in their work is more effective in the hybrid simulation of mesoscale channel flows of order O(10 2 ) nm in height.…”

Modeling of Micro/Nano Channel Flows

“…The multiscale hybrid models were developed for solving a micro channel flow in which the channel height is relatively large while the fluid-wall interfacial phenomena should be considered (Atkas and Aluru, 2002;Liu et al, 2007;Nie et al, 2004;Sun et al, 2010;Yang and Zheng, 2010;Yen et al, 2007). In this case, close to the wall is implemented an MDS or MCS (Monte Carlo simulation) scheme, while away from the wall is implemented a continuum model.…”

“…Across the channel height, there is a coupling subzone which is a transition zone of the two different schemes. Yen et al (2007) proposed that the height of the pure MDS region should be at least 12 σ for validity and sufficiently accuracy of the hybrid Frontiers in Heat and Mass Transfer (FHMT), 8, 19 (2017) DOI: 10.5098/hmt.8.19 Global Digital Central ISSN: 2151-8629 4 simulation. Better convergence can be obtained with an overlap region of at least 10 σ in height ( σ is the diameter of the fluid molecule) (Yen et al, 2007).…”