Exact Solution of AC Electro-Osmotic Flow in a Microannulus

2013 ◽  
Vol 135 (9) ◽  
Author(s):  
Ali Jabari Moghadam
Keyword(s):  
Exact Solution ◽  
Double Layer ◽  
Electric Double Layer ◽  
Maximum Velocity ◽  
Velocity Profiles ◽  
Radius Ratio ◽  
Dimensionless Frequency ◽  
Ζ Potential ◽  
Osmotic Flow ◽  
Electro Osmotic Flow

The time-periodic electro-osmotic flow in a microannulus is investigated based on the linearized Poisson–Boltzmann equation. An exact solution of the velocity distribution is obtained by using the Green's function approach. The influences of the geometric radius ratio, the wall ζ potential ratio, the electrokinetic radius, and the dimensionless frequency on velocity profiles are presented. Variations of the geometric radius ratio (between zero and one) can lead to quite different flow behaviors. The wall ζ potential ratio affects the magnitude and direction of the velocity profiles within the electric double layer near the two walls of a microannulus. Depending on the frequency and the geometric radius ratio, the walls identically and/or oppositely charged, both may result in the two-opposite-direction flow in the annulus. For high frequency, the electro-osmotic velocity variations are restricted mainly within a thin layer near the two cylindrical walls. Increasing the electrokinetic radius leads to decrease the electric double layer thickness as well as the maximum velocity near the walls.

Velocity measurements inside the diffuse electric double layer in electro-osmotic flow

2006 ◽  
Vol 89 (4) ◽  
pp. 044103 ◽  
Author(s):  
Reza Sadr ◽  
Minami Yoda ◽  
Pradeep Gnanaprakasam ◽  
A. Terrence Conlisk
Keyword(s):  
Double Layer ◽  
Electric Double Layer ◽  
Velocity Measurements ◽  
Osmotic Flow ◽  
Electro Osmotic Flow

scholarly journals INFLUENCE OF THE ELECTRIC DOUBLE LAYER ON INDUCED PRESSURE FIELDS AND DEVELOPMENT LENGTHS IN ELECTRO-OSMOTIC FLOWS

2005 ◽  
Vol 19 (28n29) ◽  
pp. 1655-1658
Author(s):  
YONGHAO ZHANG ◽  
XIAO-JUN GU ◽  
ROBERT W. BARBER ◽  
DAVID R. EMERSON
Keyword(s):  
Double Layer ◽  
Electric Double Layer ◽  
Pressure Field ◽  
Volumetric Flow Rate ◽  
Channel Height ◽  
Fluid Viscosity ◽  
Development Length ◽  
Pressure Fields ◽  
Flow Development ◽  
Electro Osmotic Flow

Electro-osmotic flow can be used as an efficient pumping mechanism in microfluidic devices. For this type of flow, frictional losses at the entrance and exit can induce an adverse longitudinal pressure distribution that can lead to dispersive effects. The present study describes a numerical investigation of the influence of the electric double layer on the induced pressure field and the flow development length. The induced pressure gradient is affected by the volumetric flow rate, fluid viscosity and the channel height. When the electric double layer is small, the development length remains constant at 0.57 of the channel height but decreases as the double layer grows in thickness.

Dispersion in Electro-Osmotic Flow Through a Slit Channel With Axial Step Changes of Zeta Potential

2013 ◽  
Vol 135 (10) ◽  
Author(s):  
Chiu-On Ng ◽  
Bo Chen
Keyword(s):  
Dispersion Coefficient ◽  
Hydrodynamic Dispersion ◽  
Plate Height ◽  
Cross Sectional ◽  
Ζ Potential ◽  
Osmotic Flow ◽  
Long Wave ◽  
Cross Sectional Dimension ◽  
Limiting Case ◽  
Electro Osmotic Flow

An analytical study is presented in this paper on hydrodynamic dispersion due to steady electro-osmotic flow (EOF) in a slit microchannel with longitudinal step changes of ζ potential. The channel wall is periodically patterned with alternating stripes of distinct ζ potentials. Existing studies in the literature have considered dispersion in EOF with axial nonuniformity of ζ potential only in the limiting case where the length scale for longitudinal variation is much longer than the cross-sectional dimension of the channel. Hence, the existing theories on EOF dispersion subject to nonuniform charge distributions are all based on the lubrication approximation, by which cross-sectional mixing is ignored. In the present study, the general case where the length of one periodic unit of wall pattern (which involves a step change of ζ potential) is comparable with the channel height, as well as the long-wave limiting case, are investigated. The problem for the hydrodynamic dispersion coefficient is solved numerically in the general case, and analytically in the long-wave lubrication limit. The dispersion coefficient and the plate height are found to have strong, or even nonmonotonic, dependence on the controlling parameters, including the period length of the wall pattern, the area fraction of the EOF-suppressing region, the Debye parameter, the Péclet number, and the ratio of the two ζ potentials.

LATTICE BOLTZMANN SIMULATION OF VISCOUS DISSIPATION IN ELECTRO-OSMOTIC FLOW IN MICROCHANNELS

2007 ◽  
Vol 18 (07) ◽  
pp. 1119-1131 ◽  
Author(s):  
ZHEN-HUA CHAI ◽  
BAO-CHANG SHI ◽  
LIN ZHENG
Keyword(s):  
Viscous Dissipation ◽  
Lattice Boltzmann ◽  
Electric Double Layer ◽  
Governing Equations ◽  
Osmotic Flow ◽  
Lattice Boltzmann Simulation ◽  
Lattice Boltzmann Models ◽  
Boltzmann Method ◽  
Electro Osmotic Flow ◽  
High Velocity Gradient

In this paper, the effects of viscous dissipation in electro-osmotic flow in microchannels are numerically analyzed with lattice Boltzmann method (LBM), and three different lattice Boltzmann models that can recover the macroscopic governing equations for electro-osmotic flow (EOF) are proposed. As the dimensions of the channels approach the microlevel, viscous dissipation could be significant due to a high velocity gradient in electric double layer (EDL). Numerical results show that viscous dissipation plays an important role in EOF in microchannels.

Research on Hydration of Waterproof-Typed Semi-Hydrated Gypsum

2011 ◽  
Vol 306-307 ◽  
pp. 909-912 ◽  
Author(s):  
Jian Quan Li ◽  
Ming Zhu Gong ◽  
Guo Zhong Li
Keyword(s):  
Growth Rate ◽  
Carboxylic Acid ◽  
Double Layer ◽  
Electric Double Layer ◽  
Hydration Process ◽  
Gypsum Crystal ◽  
Ζ Potential

The influences of saline waterproof agent composed of carboxylic acid sodium (RCOONa), Al2(SO4)3,K2SO4 on the hydration of semi-hydrated gypsum were investigated. The results showed: (1) with the concentration of K2SO4 increasing, the ζ potential rose due to the increasing K+ entering the electric double layer of gypsum; (2) with the concentration of Al2(SO4)3 heightening, the ζ potential gradually decreased as a result of the formed AFt phase during the hydration process and the increasing Al3+ entering the electric double layer of gypsum. The ζ potential rose because the RCOO-base groups adhered to the surface of gypsum crystal, which slowed down the growth rate of the gypsum crystal in direction c, and short hexahedron poles were produced.

Investigation of Combined Electro-Osmotic and Pressure-Driven Flow in Rough Microchannels

2008 ◽  
Vol 130 (6) ◽  
Author(s):  
Prashant R. Waghmare ◽  
Sushanta K. Mitra
Keyword(s):  
Surface Roughness ◽  
Velocity Profile ◽  
Velocity Profiles ◽  
Osmotic Flow ◽  
Smooth Channel ◽  
Parabolic Velocity Profile ◽  
Pressure Driven Flow ◽  
Electro Osmotic Flow ◽  
Effect Of Surface ◽  
Pressure Driven

The present study is carried out to investigate the influence of surface roughness in combined electro-osmotic and pressure-driven flow in microchannel. Two-dimensional theoretical model is developed to predict the behavior of velocity profiles in rough microchannel. The concept of surface roughness-viscosity model is used to account the effect of surface roughness. The pluglike velocity profile for electro-osmotic flow and the parabolic velocity profile for pressure-driven flow with delay in attaining the centerline velocity are observed. It is found that for electro-osmotic flow, the deviation in velocity profile from a flow in a smooth channel occurs near the wall, whereas in pressure-driven flow, such deviation is dominant in the core region. A superposition of pluglike and parabolic velocity profiles is found in combined electro-osmotic and pressure-driven flow. It is also observed that in the case of combined flow, the deviation in velocity profile from the smooth channel case reduces gradually with the distance from the wall.

scholarly journals ANALYSIS OF ELECTROSTATIC PROPERTIES OF POLYSTYRENE FOAM FILTRATION MEDIA

2019 ◽  
pp. 167-174
Author(s):  
D. V. Charnyi ◽  
Yu. A. Onanko
Keyword(s):  
Double Layer ◽  
Electric Double Layer ◽  
Aqueous Suspension ◽  
Electrostatic Charge ◽  
Main Stage ◽  
Polystyrene Foam ◽  
Ζ Potential ◽  
Electrostatic Properties ◽  
Charging Time ◽  
Different Diameters

The relevance of research. The analysis of the aqueous suspension filtration initial stage through clean polystyrene foam filtration media carried out. Such feature of its work as hydro-sorting is considered. The degree of imbalance and interaction with other electrostatic systems in aqueous suspension determines the layer of potential-forming ions, which is formed around the core of the system. It determines system’s sign and most of the electrical double layer charge. It is usually determined using a physical quantity such as electrostatic or ζ-potential. The aim of this work is to determine the electrostatic properties of polystyrene foam granules and the degree of influence on the process of retaining various nature colloidal particles on their surface when filtering an aqueous suspension through them. Research results. The relationship between the sizes of polystyrene foam granules and the concentrations of electrostatic charge on their surface analyzed. Using the Poison-Boltzmann theory, a relationship between an electrostatic charge and an electric double layer of polystyrene foam granules in aqueous suspension showed. The importance of the ζ-potential researching for controlling of colloidal suspensions filtering process substantiated. The electrostatic properties of different morphology colloids studied. Analysis of research data confirms the hypothesis of a very close connection between the various morphologies colloids ζ-potential magnitude and their electric double layer interaction force with electric double layer of polystyrene foam granules in an aqueous suspension. This means that the polystyrene foam filter “charging” time is closely connected to the values of colloids ζ-potential in the filtered aqueous suspension. Conclusions. The initial filtration stage through clean polystyrene foam media is significantly different from the main stage of filtration due to the electrostatic interaction forces predominance. The time difference of the colloidal crusts complete formation completion on polystyrene foam granules of different diameters is so insignificant that it can be neglected and this time is considered the same for polystyrene foam granules of different diameters. Regardless of the origin nature, the retention intensity of the colloids by polystyrene foam filtration media granules and, consequently, the polystyrene filter “charging” time is directly depends on their z-potential value.  

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