Experimental observations and lattice Boltzmann method study of the electroviscous effect for liquid flow in microchannels

Abstract

The existing experimental data in the literature on hydrodynamics for liquid flow in microchannels are analyzed and the reasons causing the diversities are discussed and summarized. The present experimental data for deionized water flow in glass microtubes with diameters ranging from 50 to 530 µm show that the friction factors and transition Reynolds numbers from laminar to turbulent flow are in good agreement with the conventional theoretical predictions. However, the friction factors in stainless steel microtubes with diameters of 119 and 172 µm are much higher than the conventional theoretical predictions. This discrepancy is attributed to the large surface relative roughness or dense roughness distribution in the stainless steel tubes. Numerical simulations taking into account the electroviscous effect are carried out by using the lattice Boltzmann method. The simulation results show that the electroviscous effect does not play a significant role in the flow characteristics for channel dimensions of the order of microns and hence it can be neglected in engineering applications for moderate electrical conductivity of the liquid and conductivity of the walls. From the literature review and the present test data, it is validated that for liquid flow in smooth microchannels the conventional theoretical prediction for flow characteristics should still be applied.

Non-Newtonian flow in microporous structures under the electroviscous effect

“…To be in the same framework of the lattice Boltzmann method as solving the velocity field, the following discrete lattice Boltzmann evolution equation is employed to solve the electric potential in Eq. (11) [4,24]:…”

“…Tang et al [4] conducted experiments for deionized water flowing in four smooth fuse silica microtubes (diameter D = 50.55, 74.36, 102.74, and 530.3 lm with the measured inner surface relative roughness far less than 1%) and two rough stainless steel microtubes (diameter D = 119.09, and 172.0 lm with the relative roughness 4.1%, and 5.9%, respectively). The experimental results for smooth fuse silica microtubes show that friction factors are in good agreement with the classical predictions for convectionalsized channels and the flow resistance due to the electroviscous effect is not significant.…”

An experimental study of two-phase pressure drop of acetone in triangular silicon micro-channels

“…Tang et al [31][32] thought that surface roughness may have significant effect on the pressure drop in microchannel flow, even just larger than 1%. It should be noted that the smooth silicon micro channels have nanoscale surface roughness, at least two orders to three orders of magnitude less than the conventional miniature channels fabricated with metallic material such as copper and stainless steel.…”

Lattice Boltzmann method for microfluidics: models and applications

“…On the other hand, the electrical effects can be naturally implemented into the general LBM algorithm as an external force, with the electrical field and ion concentration distributions obtained numerically from suitable numerical schemes, including the LBM-like algorithms (Melchionna and Succi 2004;Hlushkou et al 2004Hlushkou et al , 2005Tang et al 2007a;Wang et al 2006;Guo et al 2005;Wang and Chen 2007). Interestingly, Yan et al (2007) have studied the electroosmotic flow near an earthworm body surface when the earthworm moves in moist soil.…”