Molecular Dynamics Simulation of Nanoscale Channel Flows with Rough Wall Using the Virtual-Wall Model

Xiaohui Lin,Fu-Bing Bao,Jiemin Chen,Xiaoyan Gao

doi:10.1155/2018/4631253

Abstract

Molecular dynamics simulation is adopted in the present study to investigate the nanoscale gas flow characteristics in rough channels. The virtual-wall model for the rough wall is proposed and validated. The computational efficiency can be improved greatly by using this model, especially for the low-density gas flow in nanoscale channels. The effect of roughness element geometry on flow behaviors is then studied in detail. The fluid velocity decreases with the increase of roughness element height, while it increases with the increases of element width and spacing.

Highlights

Micro/nano-electromechanical systems (MEMS/NEMS) have received considerable attentions over the past two decades
Barisik and Beskok found that, in a channel with 5 nm in height, 40% of the channel is immersed in the wall force field [11]. erefore, the fluid transport characteristics, such as momentum and energy, significantly deviate from predictions of kinetic theory [11]
Molecular dynamics simulation (MD) investigates the interactions and movements of atoms and molecules, using N-body simulation [12]. is method has been employed by many researchers in the past to study the liquid flow in nanochannels [13,14,15,16]

Summary

Introduction

Micro/nano-electromechanical systems (MEMS/NEMS) have received considerable attentions over the past two decades. In the virtual-wall model, the force on a fluid atom from wall atoms can be expressed as. Perfect agreement between these two models can be found, which indicates that the virtualwall model works well in the MD simulation. In the present study, the virtual-wall model is adopted to describe the rough wall. Platinum atom cuboids on the smooth atomic wall are used to represent the roughness element, as illustrated in Figure 2. e roughness element is periodic in both x and z directions. e geometry of the roughness element is shown in Figure 2(b). e height of the roughness element is h, and the widths in x and z directions ρ (kg∙m–3) vx (m·s−1)

Atomic wall Virtual wall

Findings

Outer channel Inner channel Rough channel