Interfacial friction based quasi-continuum hydrodynamical model for nanofluidic transport of water

Abstract

In this work, we formulate a one-dimensional isothermal hydrodynamic transport model for water, which is an extension to our recently proposed hydrodynamic model for Lennard-Jones type fluid [R. Bhadauria and N. R. Aluru, J. Chem. Phys. 139, 074109 (2013)]. Viscosity variations in confinement are incorporated by the local average density method. Dirichlet boundary conditions are provided in the form of slip velocity that depends upon the macroscopic interfacial friction coefficient. The value of this friction coefficient is computed using a novel generalized Langevin equation formulation that eliminates the use of equilibrium molecular dynamics simulation. Gravity driven flows of SPC/E water confined between graphene and silicon slit shaped nanochannels are considered as examples for low and high friction cases. The proposed model yields good quantitative agreement with the velocity profiles obtained from non-equilibrium molecular dynamics simulations.

Multiscale modeling of electroosmotic flow: Effects of discrete ion, enhanced viscosity, and surface friction

“…As discussed previously, 24 we can recast Eqs. (1), (3), and (4) to provide an expression for the electroosmotic slip velocity as…”

“…The coarse grained solvent densityρ 0 along with temperature T provides an equivalent homogeneous, pure-component thermodynamic state of the solvent, which can then be utilized to compute the local purecomponent viscosity µ p (z) using an appropriate equation of state. 24 The corresponding change in the excess viscosity µ ex (z) of the solvent is dependent on the concentration of the ions. The preliminary estimates of the excess term were provided by Falkenhagen, 39 which are valid for symmetrical electrolytes, and later extended by Onsager and Fuoss 27 to account for asymmetrical electrolytes.…”

“…In this section, we present the methodology to estimate the friction ζ 0 between a charged wall and a polar solvent. We begin with the analysis first presented by Huang and Szlufarska 26 that was later adapted for SPC/E water near an uncharged wall 24 and binary mixtures. 25 The friction contribution ζ j 0 from a single solvent particle j in the interfacial region can be expressed as…”

“…22 The contact-adsorption of ions at the wall has also been linked to the increase in the solvent viscosity. 23 In our previous work, 24,25 we have characterized the slip of a single component fluid and binary mixtures using a multiscale, phenomenological Generalized Langevin Equation (GLE) based slip model. In these friction based models, we evolve the trajectories of the interfacial particles using GLE, while also accounting for the total PMF of the fluid.…”

Relation between boundary slip mechanisms and waterlike fluid behavior

“…For confined geometries the hydrodynamic equations are no longer valid, and in this case, the use of the no-slip boundary condition is at least questionable. Many experimental [1][2][3][4][5][6][7][8], theoretical, and computational [9][10][11][12][13][14][15] results report that there are several flow boundary conditions consistent with the fluid behavior and mobility [16][17][18][19] beyond the no-slip boundary condition. The amount of slip is usually measured through the magnitude of the slip length, defined as the ratio between the shear rate and the slip velocity [16][17][18][19].…”