Microscale effects of Bingham-plastic liquid behavior considering electroviscous effects in nano- or microsized circular tubes

Abstract

Although microscale phenomena are ubiquitous in fluid flow through nano- or microsized channels and pores, the mechanisms remain unclear. To clarify these mechanisms, we investigate herein Bingham-plastic liquids with electroviscous effects (EVEs) in nano- and microsized circular tubes. The constitutive equation and electroviscous forces are introduced into the governing equations, and approximate analytical solutions are obtained. Velocity reduction results from the combined effects of the Bingham characteristics and EVEs. The Bingham behavior reduces the strength of the EVE electric field, and EVEs increase the width of the flow core. The dimensionless average velocity decreases as the tube radius decreases and goes to zero upon approaching the lower limit of the movable fluid radius (Rm). As the pressure gradient decreases, the average velocity first decreases linearly, then decreases nonlinearly in a concave shape, and finally approaches zero as the pressure reaches the threshold pressure gradient (TPG). The Bingham plastic behavior causes both the Rm and the nonlinear flow with TPG, and Rm is still caused by the van der Waals forces under liquid compressibility more obviously. The EVE parameters only affect the degree of nonlinearity when the liquid exhibits Bingham-plastic behavior. These results are consistent with experimentally observed de-ionized water flowing in microscale silica tubes. We infer that the Newtonian fluid displays the Bingham-plastic behavior in nano- or microsized channels in what we call “microscale effects.” These results elucidate the mechanism that leads to nonlinear or low-speed non-Darcy flow in nano- or microsized channels and pores from the liquid characteristic and liquid-solid interaction.

Electrokinetic energy conversion through cylindrical microannulus with periodic heterogeneous wall potentials

“…The streaming potential and EKEC have been investigated in various geometric shapes [38][39][40][41][42]. Based on the experimental study of Van der Heyden et al [43], wall zeta potential and surface charge density presented by Choi and Kim [44] were utilized to describe the electrokinetic flow-induced currents in nanofluidic channels.…”

Electrokinetic energy conversion efficiency in a nanochannel with slip-dependent zeta potential

“…In recent years, the rapid development of nanofabrication technology has garnered researchers' significant attention for the study of nanometer-scale fluid materials. The phenomenon of fluid transport in nanoscale devices has a wide range of applications [1][2][3][4], including nanofluidic chips, biosensors, nanojets, droplet generators, and energy harvesting in nanometer-scale fluid channels. Among these applications, the concept of harvesting electrical energy from nanofluidic systems has increasingly captured the interest of many researchers [5][6][7][8][9][10][11].…”