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O Bautista - One of the best experts on this subject based on the ideXlab platform.
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dispersion coefficient in an electro Osmotic Flow of a viscoelastic fluid through a microchannel with a slowly varying wall zeta potential
Journal of Fluid Mechanics, 2018Co-Authors: J Arcos, F Mendez, E Bautista, O BautistaAbstract:The dispersion coefficient of a passive solute in a steady-state pure electro-Osmotic Flow (EOF) of a viscoelastic liquid, whose rheological behaviour follows the simplified Phan-Thien–Tanner (sPTT) model, along a parallel flat plate microchannel, is studied. The walls of the microchannel are assumed to have modulated and low potentials, which vary slowly in the axial direction in a sinusoidal manner. The Flow field required to obtain the dispersion coefficient was solved using the lubrication approximation theory (LAT). The solution of the electric potential is based on the Debye–Huckel approximation for a symmetric electrolyte. The viscoelasticity of the fluid is observed to notably amplify the axial distribution of the effective dispersion coefficients due to the variation in the potentials of the walls. The problem was formulated for two cases: when the Debye layer thickness (EDL) was on the order of unity (thick EDL) and in the limit where the thickness of the EDL was very small compared with the height of the microchannel (thin EDL limit). Due to the coupling between the nonlinear governing equations and the sPTT fluid model, they were replaced by their approximate linearized forms and solved in the limit of using the regular perturbation technique. Here is the amplitude of the sinusoidal function of the potentials. Additionally, the numerical solution of the simplified governing equations was also obtained for and compared with the approximate solution, showing excellent agreement for . Note that the dispersion coefficient primarily depends on the Deborah number, on the ratio of the half-height of the microchannel to the Debye length, and on the assumed variation in the potentials of the walls.
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influence of slip wall effect on a non isothermal electro Osmotic Flow of a viscoelastic fluid
International Journal of Thermal Sciences, 2015Co-Authors: A Matias, S Sanchez, F Mendez, O BautistaAbstract:Abstract We present an analytical model that predicts the influence of Joule heating on the slip velocity in an electro-Osmotic Flow (EOF) of viscoelastic fluids. The viscoelasticity of the fluid is taken into account by employing the simplified Phan-Thien and Tanner constitutive model (sPTT). The Joule heating induces temperature gradients along the microchannel making properties non-uniform and hence alters the electric potential and the Flow field. In consequence, the slip velocity and the velocity gradient on the microchannel surface are drastically modified in comparison with the case of uniform properties. Using the well-known lubrication theory, the momentum equations together with the energy, Poisson and Ohmic current conservation equations are considerably simplified. The dimensionless mathematical model is solved by using a regular perturbation technique, which is compared against a numerical solution. The results show that using hydrophobic microchannels, for the used values of the parameters involved in this analysis, the volumetric Flow rate through microchannels can be massively amplified in about 400%, in comparison with the case of non-slipping surfaces. In addition, by using hydrophobic microchannels, the maximum temperature in the microchannel can be substantially reduced.
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lubrication theory for electro Osmotic Flow in a slit microchannel with the phan thien and tanner model
Journal of Fluid Mechanics, 2013Co-Authors: O Bautista, S Sanchez, J Arcos, F MendezAbstract:In this work the purely electro-Osmotic Flow of a viscoelastic liquid, which obeys the simplified Phan-Thien-Tanner (sPTT) constitutive equation, is solved numerically and asymptotically by using the lubrication approximation. The analysis includes Joule heating effects caused by an imposed electric field, where the viscosity function, relaxation time and electrical conductivity of the liquid are assumed to be temperature-dependent. Owing 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 microchannel, which in turn modifies the normal plug-like electro-Osmotic velocity profiles. 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. Also, the finite thermal conductivity of the microchannel wall was considered in the analysis. 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. A comparison between the numerical predictions and the asymptotic solutions was made, and reasonable agreement was found.
F Mendez - One of the best experts on this subject based on the ideXlab platform.
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dispersion coefficient in an electro Osmotic Flow of a viscoelastic fluid through a microchannel with a slowly varying wall zeta potential
Journal of Fluid Mechanics, 2018Co-Authors: J Arcos, F Mendez, E Bautista, O BautistaAbstract:The dispersion coefficient of a passive solute in a steady-state pure electro-Osmotic Flow (EOF) of a viscoelastic liquid, whose rheological behaviour follows the simplified Phan-Thien–Tanner (sPTT) model, along a parallel flat plate microchannel, is studied. The walls of the microchannel are assumed to have modulated and low potentials, which vary slowly in the axial direction in a sinusoidal manner. The Flow field required to obtain the dispersion coefficient was solved using the lubrication approximation theory (LAT). The solution of the electric potential is based on the Debye–Huckel approximation for a symmetric electrolyte. The viscoelasticity of the fluid is observed to notably amplify the axial distribution of the effective dispersion coefficients due to the variation in the potentials of the walls. The problem was formulated for two cases: when the Debye layer thickness (EDL) was on the order of unity (thick EDL) and in the limit where the thickness of the EDL was very small compared with the height of the microchannel (thin EDL limit). Due to the coupling between the nonlinear governing equations and the sPTT fluid model, they were replaced by their approximate linearized forms and solved in the limit of using the regular perturbation technique. Here is the amplitude of the sinusoidal function of the potentials. Additionally, the numerical solution of the simplified governing equations was also obtained for and compared with the approximate solution, showing excellent agreement for . Note that the dispersion coefficient primarily depends on the Deborah number, on the ratio of the half-height of the microchannel to the Debye length, and on the assumed variation in the potentials of the walls.
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influence of slip wall effect on a non isothermal electro Osmotic Flow of a viscoelastic fluid
International Journal of Thermal Sciences, 2015Co-Authors: A Matias, S Sanchez, F Mendez, O BautistaAbstract:Abstract We present an analytical model that predicts the influence of Joule heating on the slip velocity in an electro-Osmotic Flow (EOF) of viscoelastic fluids. The viscoelasticity of the fluid is taken into account by employing the simplified Phan-Thien and Tanner constitutive model (sPTT). The Joule heating induces temperature gradients along the microchannel making properties non-uniform and hence alters the electric potential and the Flow field. In consequence, the slip velocity and the velocity gradient on the microchannel surface are drastically modified in comparison with the case of uniform properties. Using the well-known lubrication theory, the momentum equations together with the energy, Poisson and Ohmic current conservation equations are considerably simplified. The dimensionless mathematical model is solved by using a regular perturbation technique, which is compared against a numerical solution. The results show that using hydrophobic microchannels, for the used values of the parameters involved in this analysis, the volumetric Flow rate through microchannels can be massively amplified in about 400%, in comparison with the case of non-slipping surfaces. In addition, by using hydrophobic microchannels, the maximum temperature in the microchannel can be substantially reduced.
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lubrication theory for electro Osmotic Flow in a slit microchannel with the phan thien and tanner model
Journal of Fluid Mechanics, 2013Co-Authors: O Bautista, S Sanchez, J Arcos, F MendezAbstract:In this work the purely electro-Osmotic Flow of a viscoelastic liquid, which obeys the simplified Phan-Thien-Tanner (sPTT) constitutive equation, is solved numerically and asymptotically by using the lubrication approximation. The analysis includes Joule heating effects caused by an imposed electric field, where the viscosity function, relaxation time and electrical conductivity of the liquid are assumed to be temperature-dependent. Owing 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 microchannel, which in turn modifies the normal plug-like electro-Osmotic velocity profiles. 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. Also, the finite thermal conductivity of the microchannel wall was considered in the analysis. 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. A comparison between the numerical predictions and the asymptotic solutions was made, and reasonable agreement was found.
Pranab Kumar Kundu - One of the best experts on this subject based on the ideXlab platform.
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effects of slip velocity on rotating electro Osmotic Flow in a slowly varying micro channel
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2016Co-Authors: Gopal Chandra Shit, A. Mondal, A Sinha, Pranab Kumar KunduAbstract:Abstract In this paper, we have studied the effects of slip velocity on rotating electro-Osmotic Flow in a non-uniform micro-channel. Electro-Osmotically driven fluid Flow takes place in a micro-channel with flexible walls in a rotating system. The potential electric field is applied along the length of the micro-channel describing the Poisson–Boltzmann equation. We assume that the entire system is rotating about the height of the channel. The non-linear Poisson–Boltzmann equation is solved numerically based upon which a Crank–Nicolson numerical scheme is developed for obtaining velocity distribution. With an aim to validate our numerical results a comparison has been made with the previous study in the case of no-slip condition and found to be good agreement.
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electro Osmotic Flow of a viscoelastic fluid in a channel applications to physiological fluid mechanics
Applied Mathematics and Computation, 2011Co-Authors: J C Misra, Gopal Chandra Shit, S Chandra, Pranab Kumar KunduAbstract:The paper presents a comprehensive theoretical study on the electro-Osmotic Flow of a viscoelastic fluid past a channel having stretching walls. An attempt has been made to investigate the effect of rheological and electro-Osmotic parameters on the kinematics of the fluid. Results presented here pertain to the case where the channel height is much greater than the thickness of electrical double layer comprising the Stern and diffuse layers. The study reveals that an increase in electro-Osmotic parameter leads to an increase in the axial velocity throughout the channel for a fluid having viscoelastic coefficient equal to that of blood. This aspect provides a source of novel insight into the process of designing bio-sensing and micro-fluidic devices.
Changyi Wang - One of the best experts on this subject based on the ideXlab platform.
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rotating electro Osmotic Flow over a plate or between two plates
Physical Review E, 2011Co-Authors: Chien Cheng Chang, Changyi WangAbstract:In this paper, we investigate rotating electro-Osmotic (EO) Flow over an infinite plate or in a channel formed by two parallel plates. The analysis is based on the Debye-Huckel approximation for charge distributions and the Navier-Stokes equation for a transport electrolyte in the rotating frame. It is shown that, for the single plate, the nondimensional speed of system rotation ω is the singly most important parameter, while for the channel, in addition to ω, the nondimensional electrokinetic width K also plays an important role. However, the parameter ω≡η(2) has different natural appearances in the respective cases of a single plate (SP) and two plates (TPs). More precisely, η(SP) measures the ratio λ(D)/L(K) of the Debye length to the Ekman depth, while η(TP) measures the ratio L/L(K) of the channel width to the Ekman depth. The effect of rotation is always to reduce the axial Flow rate along the direction of the applied electric field, accompanied by a (secondary) transverse Flow. In the SP case, the plot on the velocity plane for each ω shows an interesting closed EO Ekman spiral. The size of the spiral shrinks with increasing ω. The transverse Flow is so significant that the volume transport associated with the EO Ekman spiral turns clockwise 45° to the applied field near ω=0 and gradually turns at a right angle to the applied field as ω is increased. In contrast, in the TP case, the transverse Flow rate is smaller than the axial Flow rate when ω is small. The transverse Flow rates at all K are observed to reach their maxima at ω of order 1. The volume transport is nearly at a zero angle to the applied field near ω=0 and gradually turns to 45° to the applied field as ω is increased. In the limit of ω→∞, for both SP and TP cases, the entire system forms a rigid body rotation-there is neither axial nor transverse Flow.
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analytical solution of electro Osmotic Flow in a semicircular microchannel
Physics of Fluids, 2008Co-Authors: Changyi Wang, Yinghong Liu, Chien C ChangAbstract:The electro-Osmotic Flow through a microchannel with a semicircular cross section is studied under the Debye–Huckel approximation. Analytical series solutions are found for two basic cases. The solutions for the two basic cases considered can be superposed to yield solutions for any combination of constant zeta potentials on the flat or curved wall boundaries. Moreover, in the limit of a thin electric double layer (small Debye length compared to the nominal dimension), a method of solution is shown for variable zeta potentials by using the Smoluchowski slip approximation.
J Arcos - One of the best experts on this subject based on the ideXlab platform.
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dispersion coefficient in an electro Osmotic Flow of a viscoelastic fluid through a microchannel with a slowly varying wall zeta potential
Journal of Fluid Mechanics, 2018Co-Authors: J Arcos, F Mendez, E Bautista, O BautistaAbstract:The dispersion coefficient of a passive solute in a steady-state pure electro-Osmotic Flow (EOF) of a viscoelastic liquid, whose rheological behaviour follows the simplified Phan-Thien–Tanner (sPTT) model, along a parallel flat plate microchannel, is studied. The walls of the microchannel are assumed to have modulated and low potentials, which vary slowly in the axial direction in a sinusoidal manner. The Flow field required to obtain the dispersion coefficient was solved using the lubrication approximation theory (LAT). The solution of the electric potential is based on the Debye–Huckel approximation for a symmetric electrolyte. The viscoelasticity of the fluid is observed to notably amplify the axial distribution of the effective dispersion coefficients due to the variation in the potentials of the walls. The problem was formulated for two cases: when the Debye layer thickness (EDL) was on the order of unity (thick EDL) and in the limit where the thickness of the EDL was very small compared with the height of the microchannel (thin EDL limit). Due to the coupling between the nonlinear governing equations and the sPTT fluid model, they were replaced by their approximate linearized forms and solved in the limit of using the regular perturbation technique. Here is the amplitude of the sinusoidal function of the potentials. Additionally, the numerical solution of the simplified governing equations was also obtained for and compared with the approximate solution, showing excellent agreement for . Note that the dispersion coefficient primarily depends on the Deborah number, on the ratio of the half-height of the microchannel to the Debye length, and on the assumed variation in the potentials of the walls.
-
lubrication theory for electro Osmotic Flow in a slit microchannel with the phan thien and tanner model
Journal of Fluid Mechanics, 2013Co-Authors: O Bautista, S Sanchez, J Arcos, F MendezAbstract:In this work the purely electro-Osmotic Flow of a viscoelastic liquid, which obeys the simplified Phan-Thien-Tanner (sPTT) constitutive equation, is solved numerically and asymptotically by using the lubrication approximation. The analysis includes Joule heating effects caused by an imposed electric field, where the viscosity function, relaxation time and electrical conductivity of the liquid are assumed to be temperature-dependent. Owing 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 microchannel, which in turn modifies the normal plug-like electro-Osmotic velocity profiles. 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. Also, the finite thermal conductivity of the microchannel wall was considered in the analysis. 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. A comparison between the numerical predictions and the asymptotic solutions was made, and reasonable agreement was found.
