A quasi-continuum hydrodynamic model for slit shaped nanochannel flow

Abstract

We propose a quasi-continuum hydrodynamic model for isothermal transport of Lennard-Jones fluid confined in slit shaped nanochannels. In this work, we compute slip and viscous contributions independently and superimpose them to obtain the total velocity profile. Layering of fluid near the interface plays an important role in viscous contribution to the flow, by apparent viscosity change along the confining dimension. This relationship necessitates computing density profiles, which is done using the recently proposed empirical-potential based quasi-continuum theory [A. V. Raghunathan, J. H. Park, and N. R. Aluru, J. Chem. Phys. 127, 174701 (2007)]. Existing correlations for density dependent viscosity provided by Woodcock [AIChE J. 52, 438 (2006)] are used to compute viscosity profile in the nanopores. A Dirichlet type slip boundary condition based on a static Langevin friction model describing center-of-mass motion of fluid particles is used, the parameters of which are dependent on the fluctuations of total wall-fluid force from an equilibrium molecular dynamics simulation. Different types of corrugated surfaces are considered to study wall-fluid friction effects on boundary conditions. Proposed hydrodynamic model yields good agreement of velocity profiles obtained from non-equilibrium molecular dynamics simulations for gravity driven flow.

Gradient models in molecular biophysics: progress, challenges, opportunities

“…Nanofluidic devices offer diverse opportunities for biomolecule detection for medicine and security [61], and at this scale nonlocal theories offer more realism [27]. In this area, Aluru et al have developed quasicontinuum model [62] for the problem of nanoconfined fluids [63]. …”

The Effect of Wall Shear Stress and Viscous Heating on Nanoscale Flow

“…Previous studies have reported that the average density in nano-channel of smaller heights becomes lower than the density at the bulk flow region [49,51,53] for force driven flow. In addition, the magnitude of the average density has been found to decrease with the reduction in the channel height [7,37,43] and to be independent on magnitude of the applied force (wall shear stress) [39,41,50].…”

“…For decades, the slip at fluid solid interface has been under extensive studies [10,23,26,33]; and many recent experiments showed the violation of noslip boundary condition. Multiple studies have been conducted to investigate the effect of applied shear rate, channel size [29,43], nanotube diameter [41,45], pressure [27], ratio of wall-liquid density [47], and surface wettability (hydrophobicity) [7,35]on the slip length.…”

An EQT-based cDFT approach for a confined Lennard-Jones fluid mixture

“…For instance, the velocity profile of a nanoconfined fluid between two surfaces is strongly influenced by the density oscillations. 6,7 Hence, an accurate and thorough understanding of this inhomogeneous behavior is central for many applications in the field of nanotechnology.…”