Electroosmotic Flow Of non-Newtonian Fluid Research Articles

Impact of Ion Partitioning Effect on the Electroosmotic Flow of Non-Newtonian Fluid and Ion Selectivity through Soft Nanochannel

Impact of Ion Partitioning Effect on the Electroosmotic Flow of Non-Newtonian Fluid and Ion Selectivity through Soft Nanochannel

Enhanced electroosmotic mixing of non-Newtonian fluids in a heterogeneous surface charged micromixer with obstacles

We investigate the mixing and hydrodynamic characteristics computationally for a pure electroosmotic flow of non-Newtonian fluid through a nonuniformly charged micromixer with obstacles arranged in staggered and inline orders. The constitutive behavior of the fluids is described by the power-law model. We present the results by varying the dimensionless zeta potential (|ζ|), Debye parameter (κ), and power-law index (n) in the range of 1 ≤ |ζ| ≤ 8, 0.5 ≤ κ ≤ 100 and 0.5 ≤ n ≤ 1.5, respectively. The mixing is strongly influenced by the rheology of the fluids and the formation of the recirculatory zones. For the overlapped EDL (κ = 0.5), mixing efficiency (ME) decreases with n for lower |ζ| values, while ME increases with n for higher |ζ| values for both the orientation of obstacles. When the obstacles are arranged in a staggered manner, the variation of ME with n follows a decreasing-increasing trend for the intermediate values of |ζ|. The value of ME is higher for the inline arrangement with overlapped EDL (κ = 0.5) and is close to 100%. For thinner EDL (κ = 100), the value of ME is higher for inline arrangement only for |ζ|= 1 and 0.5 ≤ n ≤ 0.6, and for all other cases, it is higher for staggered arrangement. The presence of heterogeneous charged surface always enhances the mixing and the enhancement is always higher for shear-thickening fluid and for the staggered order of the obstacles. The present design of electroosmotic micromixer handling with non-Newtonian fluids provides a higher mixing efficiency as compared to most of the existing designs available in the literature. The values of n, κ and |ζ| are identified for the micromixer with two orientations of the obstacles for quick and efficient mixing and the findings may be helpful to design an efficient micromixer for the point-on care diagnostic applications handling with of non-Newtonian fluids.

RETRACTED: Theoretical study of MHD electro-osmotically flow of third-grade fluid in micro channel

• MHD electro-osmotic flow of non-Newtonian fluid. • Perturbation and Pseudo-Spectral collocation methods. • Velocity of the fluid retards subject to strong magnetic fields. • Velocity and temperature diminishing via electro-kinetic parameter Γ 2 . The electro-osmatic flow of non-newtonian fluid in a micro-channel is investigated in this article. The governing equations are derived with the help of a stress tensor then later transformed into dimensionless form with non-dimensional quantities. The perturbation method is used to obtain the approximate analytical solution of the given problem. The viscosity of the fluid is taken as a variable in terms of temperature. The validity of the perturbation solution is provided. The Pseudo-spectral collocation method is used to calculate the error in the perturbation solution of velocity and temperature. The magnitude of error in velocity and temperature is 10 −4 and 10 −2 , respectively. The impact of emerging parameters on velocity and heat profiles is also presented. The computational results reveal that the velocity profile diminishing via non-Newtonian parameter Γ 1 , electro-kinetic parameter Γ 2 , magnetic field parameter M and viscosity parameter D while an opposite behavior is noted in the velocity versus pressure gradient parameter Γ 3 , viscosity parameter E and wall's temperature θ w , respectively. Further, the temperature profile increases against the enhancement of Brinkman number, Joule heating parameter, pressure gradient parameter, wall's temperature, viscosity parameter D while reverse behavior is observed via electro-kinetic and magnetic field parameters. This study will help to understand the basic idea of MHD electro osmotic flow of non-Newtonian fluid bounded within a microchannel under the influence of variable viscosity. Further, this research can be useful to design the different types of biomedical lab-on-a-chip and thermal microfluidic devices. The developed devices can be helpful in DNA analysis and biomedical diagnosis etc.

Heat transfer analysis of MHD and electroosmotic flow of non-Newtonian fluid in a rotating microfluidic channel: an exact solution

Heat transfer analysis of MHD and electroosmotic flow of non-Newtonian fluid in a rotating microfluidic channel: an exact solution

Sinusoidal motion of small particles through a Darcy-Brinkman-Forchheimer microchannel filled with non-Newtonian fluid under electro-osmotic forces

This article deals with the electro-osmotic flow of non-Newtonian fluid in the presence of small particles moving in the sinusoidal form in a Darcy-Brinkman-Forchheimer medium. A transverse magnetic field is applied by ignoring the effects of an induced magnetic field with a small magnetic Reynolds number. To examine the non-Newtonian effects, Jeffrey fluid model is considered. The proposed mathematical modeling is based on the Poisson–Boltzmann equation, Debye length approximation, and ionic Nernst Planck equation. The modeled problem is formulated in a fixed frame, which is further transformed into a wave frame. Lubrication theory is also taken into account. Analytical solutions of nonlinear equations are obtained by using perturbation method. The impact of all the parameters is discussed for both fluid- and particulate-phases. The present effects are beneficial in designing and manufacturing microfluidics devices to determine the transport mechanism.

Electroosmotic Flow of Non-Newtonian Fluid in Porous Polymer Membrane at High Zeta Potentials.

To help in the efficient design of fluid flow in electroosmotic pumps, electroosmotic flow of non-Newtonian fluid through porous polymer membrane at high zeta potentials is studied by mainly evaluating the total flow rate at different physical parameters. Non-Newtonian fluid is represented by the power-law model and the porous polymer membrane is considered as arrays of straight cylindrical pores. The electroosmotic flow of non-Newtonian fluid through a single pore is studied by solving the complete Poisson–Boltzmann equation and the modified Cauchy momentum equation. Then assuming the pore size distribution on porous polymer membrane obeys Gaussian distribution, the performance of electroosmotic pump operating non-Newtonian fluid is evaluated by computing the total flow rate of electroosmotic flow through porous polymer membrane as a function of flow behavior index, geometric parameters of porous membrane, electrolyte concentration, applied voltage, and zeta potential. It is found that enhancing zeta potential and bulk concentration rather than the applied voltage can also significantly improve the total flow rate in porous polymer membrane, especially in the case of shear thinning fluid.

Effects of radiative heat flux and joule heating on electro-osmotically flow of non-Newtonian fluid: Analytical approach

BackgroundThe motion of fluids through the micro-tube, micro-channel, membranes, porous material and other fluid conduits because of the applied potential is known as electro-osmotic flow. The electro-osmosis process is a process in which electrodes generate the flow, and these electrodes are placed at each end of the micro-channel in the reservoirs. The electro-osmotic flow is induced through the surface charge in a small amount. The surface of most channels is made of glass and polymer which in an electrolyte solution have a negative charge. The reason for this is the abundance of positively charged anions in the double layer close to the channel walls. Because of the channel's electrical potential, the electrostatic forces attract the excess charges in the double layer and move towards the negative electrode.An electro-osmotic flow of non-Newtonian fluids is of significant importance in micro-fluidic systems and micro-devices. Due to the importance of electro-osmotic flow, under the influence of radiative heat flux, a theoretical analysis is conducted in this study to investigate the important characteristics of the electro-osmotic flow of third-grade fluid in the microplate. The viscosity of the fluid is either constant or temperature-dependent. The results are compared with experimental work done on a Newtonian fluid. This investigation for the third-grade fluid under the radiative heat flux and variable viscosity has not been reported previously to the best of our knowledge. Method of solutionUsing the perturbation method, the approximate analytical solution to the problem of the nonlinear boundary value is obtained. The perturbation method is a relatively simple and high-precision method, that is used to find the approximate analytical solutions. In each case of the viscosity model, the analytical expressions of the velocity and temperature profiles are presented. Computational results and conclusionsThe effects of fluidic parameters on velocity and temperature profiles of electro-osmotic flows are discussed graphically. The computational results show that the velocity and temperature decrease against the radiation parameter, non-Newtonian parameter and electro-kinetic parameter. ApplicationsIn the first step, the results of this study provide a useful insight into the basic idea of the electro-osmotic flow of third-grade fluid within a micro-channel with the variable properties and thermal radiation in parallel geometry. Besides, the current study could be beneficial in the design of various biomedical lab-on-chip devices. These devices can be used for the transport of liquids in narrow containment (sample injection) and the production of chemical waste. These devices can also be useful for biomedical diagnosis and analysis (i.e. DNA analysis and clinical detection of viruses and bacteria etc.). Our analysis can also be used by designers of the thermal microfluidic devices. The efficiency of the heating techniques of the microfluidic system can be increased. It can also be used to enhance and control on-chip heat transfer, which increases the capacity of the polymeric microfluidic system.

Electroosmotic flow of non-Newtonian fluids in a constriction microchannel.

Insulator-based dielectrophoresis has to date been almost entirely restricted to Newtonian fluids despite the fact that many of the chemical and biological fluids exhibit non-Newtonian characteristics. We present herein an experimental study of the fluid rheological effects on the electroosmotic flow of four types of polymer solutions, i.e., 2000 ppm xanthan gum (XG), 5% polyvinylpyrrolidone (PVP), 3000 ppm polyethylene oxide (PEO), and 200 ppm polyacrylamide (PAA) solutions, through a constriction microchannel under DC electric fields of up to 400 V/cm. We find using particle streakline imaging that the fluid elasticity does not change significantly the electroosmotic flow pattern of weakly shear-thinning PVP and PEO solutions from that of a Newtonian solution. In contrast, the fluid shear-thinning causes multiple pairs of flow circulations in the weakly elastic XG solution, leading to a central jet with a significantly enhanced speed from before to after the channel constriction. These flow vortices are, however, suppressed in the strongly viscoelastic and shear-thinning PAA solution.

DPD simulation of non-Newtonian electroosmotic fluid flow in nanochannel

ABSTRACTWe use the dissipative particle dynamics (DPD) method to simulate the non-Newtonian electroosmotic flow (EOF) through nanochannels. Contrary to a large amount of past computational efforts dedicated to the study of EOF profile, this work pays attention to the EOF of non-Newtonian fluids, which has been rarely touched in past publications. Practically, there are many MEMS/NEMS devices, in which the EOF behaviour should be treated assuming both non-continuum and non-Newtonian conditions. Therefore, our concern in this work is to simulate the EOF through nanochannels considering both non-Newtonian fluid properties and non-continuum flow conditions. We have chosen DPD as our working tool because it provides several important advantages comparing with the classical time consuming molecular dynamics method. Using the DPD method, we explore the effect of a few important fluid properties and nanochannel parameters on the EOF behaviour and the resulting flow rate magnitudes. Our investigation will result in a number of findings, which have not been reported in past research works.

Electroosmotic flow of power-law fluids in curved rectangular microchannel with high zeta potentials

In this article, electroosmotic flow of non-Newtonian fluids through a curved rectangular microchannel is studied numerically. The power-law model is used to simulate the rheological behavior of fluid. Moreover, the flow is assumed to be hydrodynamically fully developed and the walls carry high zeta potentials. To do so, the Poisson–Boltzmann equation without imposing the Debye–Hückel linear approximation is solved by applying the central difference scheme. Furthermore, the continuity and Cauchy momentum equations in the cylindrical coordinate system are solved using SIMPLE finite-volume method. Consequently, the effects of governing parameters such as flow behavior index, electrokinetic separation distance, curvature, zeta potential, and channel aspect ratio on the flow field and hydrodynamic characteristics are studied in details. The results show that the secondary flows which are created in shear-thinning fluid flows are stronger in comparison to that of shear-thickening and Newtonian fluid flows. Also, the variation of electrokinetic separation distance changes the secondary flow patterns in shear-thinning fluid flows, and it does not have a monotonic effect on the strength of secondary flows. Moreover, the obtained results for shear-thinning and Newtonian fluid flows indicate that the increasing of curvature, in addition to increasing the circulation strength considerably, also causes the volumetric flow rate to slightly increase. Furthermore, it is found that the increasing of zeta potential can be employed in shear-thinning fluid flows in order to significantly increase the volumetric flow rate and the performance of mixing. Additionally, it is observed that the increasing of channel aspect ratio leads to an increase in the circulation strength of shear-thinning fluid flow.

Electro-osmotic flow of Eyring fluids in a circular microtube with Navier's slip boundary condition

Electro-osmotic flows of non-Newtonian fluids play an important role in microdevices and microfluidic systems. A theoretical and numerical analyses are conducted to explore the characteristics of electro-osmotic flow of non-Newtonian Eyring fluids in a circular microtube under the Navier's slip boundary condition. The exact solution of velocity distribution as well as corresponding approximate solution is obtained. The effects of slip length, electrokinetic parameter and non-Newtonian characteristics on the electro-osmotic flows are discussed and plotted graphically.

Time-periodic Electroosmotic Flow of Non-newtonian Fluids in Microchannels

The alternating current electroosmotic flow of a non-Newtonian power-law fluid is studied in a circular microchannel. A numerical method is employed to solve the non-linear Poisson-Boltzmann and the momentum equations. The main parameters which affect the flow field are the flow behavior index, the dimensionless zeta potential and the dimensionless frequency. At very low dimensionless frequencies (slow oscillatory motion, small channel size, or large effective viscosity), the plug-like velocity profiles similar to steady-state electroosmotic flow are observed at nearly all times. At very high dimensionless frequencies, the flow is shown to be restricted to a thin region near the channel wall, while the bulk fluid remains essentially stationary. Velocity distributions of pseudoplastics and dilatants may be widened at low values of the dimensionless frequency depending on the dimensionless zeta potential; at high dimensionless frequencies, however, both fluids represent enhanced velocity magnitudes with the dimensionless zeta potential. In the case of high shear rate and/or suddenly-started flows, pseudoplastics tend to produce higher velocities than dilatants. These two kinds of fluids may produce same velocity profiles relying on the value of the dimensionless zeta potential as well as the ratio of their flow behavior indexes.

Entropy Generation Minimization in an Electroosmotic Flow of Non-Newtonian Fluid: Effect of Conjugate Heat Transfer

We investigate the entropy generation characteristics of a non-Newtonian fluid in a narrow fluidic channel under electrokinetic forcing, taking the effect of conjugate heat transfer into the analysis. We use power-law model to describe the non-Newtonian fluid rheology, in an effort to capture the essential thermohydrodynamics. We solve the conjugate heat transfer problem in an analytical formalism using the thermal boundary conditions of third kind at the outer surface of the walls. We bring out the alteration in the entropy generation behavior as attributable to the rheology-driven alteration in heat transfer, coupled with nonlinear interactions between viscous dissipation and Joule heating originating from electroosmotic effects. We unveil optimum values of different parameters, including both the geometric as well as thermophysical parameters, which lead to the minimization of the entropy generation rate in the system. We believe that the inferences obtained from the present study may bear far ranging consequences in the design of various cooling and heat removal devices/systems, for potential use in microscale thermal management.

Joule heating effect on a purely electroosmotic flow of non-Newtonian fluids in a slit microchannel

A theoretical analysis, based on the lubrication theory, of the Joule heating effect on a purely electroosmotic flow (EOF) of non-Newtonian fluids through a slit microchannel is presented. The Joule heating effects are caused by an imposed electric field, where the zero-shear-rate viscosity and electrical conductivity of the liquid are assumed temperature-dependent. Due to Joule heating effects, temperature gradients in the liquid make the fluid properties change within the microchannel, altering the electric potential and flow fields. A consequence of the above is the appearance of an induced pressure gradient along the micro-channel, which in turn modifies the normal plug-like electroosmotic velocity profiles. This modification of the electroosmotic fluid flow could cause significantly higher dispersion than that from parabolic-like electrophoretic flow profile, limiting its use. In addition, it is pointed out that, depending on the fluid rheology and the used values of the dimensionless parameters, the velocity, temperature and pressure profiles in the fluid are substantially modified. The dimensionless temperature profiles in the fluid and the microchannel wall are obtained as function of the dimensionless parameters involved in the analysis, and the interactions between the coupled momentum, thermal energy, and potential electric equations are examined in detail.

Pressure-driven and electroosmotic non-Newtonian flows through microporous media via lattice Boltzmann method

The lattice Boltzmann method is developed to simulate the pressure-driven flow and electroosmotic flow of non-Newtonian fluids in porous media based on the representative elementary volume scale. The flow through porous media was simulated by including the porosity into the equilibrium distribution function and adding a non-Newtonian force term to the evolution equation. The non-Newtonian behavior is considered based on the Herschel–Bulkley model. The velocity results for pressure-driven non-Newtonian flow agree well with the analytical solutions. For the electroosmotic flow, the influences of porosity, solid particle diameter, power law exponent, yield stress and electric parameters are investigated. The results demonstrate that the present lattice Boltzmann model is capable of modeling non-Newtonian flow through porous media.

Electroosmotic flow of non-Newtonian fluid in microchannels

Understanding electroosmotic flow of non-Newtonian fluid in microchannels is of both fundamental and practical significance for optimal design and operation of various microfluidic devices. A numerical study of electroosmotic flow in microchannels considering the non-Newtonian behavior has been carried out for the first time. One lattice Boltzmann equation is solved to obtain the electric potential distribution in the electrolyte, and another lattice Boltzmann equation which avoids the derivations of the velocity data to calculate the shear is applied to obtain the flow field for commonly used power-law non-Newtonian model. The simulation results show that the fluid rheological behavior is capable of changing the electroosmotic flow pattern significantly and the power-law exponent n plays an important role. For the shear thinning fluid of n < 1, the electrical double layer effect is confined to a smaller zone close to the wall surface and it is more inclined to develop into a plug-like flow whilst the shear thickening fluid of n > 1 is more difficult to grow into the plug-like flow compared to Newtonian fluid.