Dissolutive flow in nanochannels: transition between plug-like and Poiseuille-like
Q Miao and QZ Yuan and YP Zhao, MICROFLUIDICS AND NANOFLUIDICS, 22, 141 (2018).
Dynamic properties of dissolutive flow in nanochannels were investigated by molecular dynamics simulations. It turned out that the liquid flow pattern changes greatly after the dissolution effect taken into consideration. Liquid inside the channel has a plug-like velocity profile when the dissolubility is low, whereas a Poiseuille-like flow was observed as the dissolubility increases. By introducing the dissolution term to molecular kinetic theory, we explained the physical mechanisms of velocity transition. During which a modified dimensionless Galilei number was proposed to describe the effect of main forces. The results showed that in pressure-driven flow, when the dissolubility is low, the dominant dissipation is the viscous dissipation and the theoretical model of insolubility is acceptable. However, as the dissolubility increases, the dissolving dissipation takes priority, which results in the velocity profiles becoming Poiseuille-like. In addition, we analyzed the evolution of fluid density, number of dissolved solid particles and concentration distribution of solute. The liquid density varying from layered oscillation to uniform distribution was obtained, which can be described by a critical number. The analysis of solute concentration helps to establish the scaling relation among the dissolution rate, convection velocity, and diffusion coefficient. These findings not only help to understand the physical mechanisms of dissolutive flow but also help to control and optimize the flow patterns in dissoluble channels.
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