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.

Influence of Three-Dimensional Roughness on Pressure-Driven Flow Through Microchannels

2003 ◽  
Vol 125 (5) ◽  
pp. 871-879 ◽  
Author(s):  
Yandong Hu ◽  
Carsten Werner ◽  
Dongqing Li
Keyword(s):  
Surface Roughness ◽  
Pressure Drop ◽  
Roughness Element ◽  
Three Dimensional ◽  
Channel Height ◽  
Roughness Effect ◽  
Microscale Flow ◽  
Roughness Elements ◽  
Pressure Driven Flow ◽  
Pressure Driven

Surface roughness is present in most of the microfluidic devices due to the microfabrication techniques or particle adhesion. It is highly desirable to understand the roughness effect on microscale flow. In this study, we developed a three-dimensional finite-volume-based numerical model to simulate pressure-driven liquid flow in microchannels with rectangular prism rough elements on the surfaces. Both symmetrical and asymmetric roughness element arrangements were considered, and the influence of the roughness on pressure drop was examined. The three-dimensional numerical solution shows significant effects of surface roughness in terms of the rough elements’ height, size, spacing, and the channel height on both the velocity distribution and the pressure drop. The compression-expansion flow around the three-dimensional roughness elements and the flow blockage caused by the roughness in the microchannel were discussed. An expression of the relative channel height reduction due to roughness effect was presented.

EFFECT OF SURFACE ROUGHNESS ON MASS TRANSFER IN A FLAT-PLATE MICROCHANNEL BIOREACTOR

2005 ◽  
Vol 19 (28n29) ◽  
pp. 1559-1562 ◽  
Author(s):  
Y. ZENG ◽  
T. S. LEE ◽  
P. YU ◽  
H. T. LOW
Keyword(s):  
Mass Transfer ◽  
Surface Roughness ◽  
Flat Plate ◽  
Species Concentration ◽  
Solute Depletion ◽  
Smooth Channel ◽  
Dimensional Parameters ◽  
Microfabrication Technique ◽  
Volume Method ◽  
Effect Of Surface

Surface roughness exists in most microfluidic devices due to the microfabrication technique or particle adhesion. In this study, a numerical model based on Finite Volume Method has been developed to simulate the mass transfer in a flat-plate microchannel bioreactor with semi-circular protrusions uniformly distributed on the bottom. The results show that the mass transfer in rough channel is enhanced, as shown by lower minimum species concentration in the rough channel compared with that in smooth channel. Non-dimensional parameters such as Peclet number (Pe), Damkohler number (Da) and the roughness size ratio (β) can influence the effect of roughness greatly. However, it is important to ensure that the minimum species concentration in the rough channel is adequate for cell growth. The results would provide guidance on the perfusion requirements to avoid solute depletion or toxicity during cell culture.

Numerical study on the rotating electro-osmotic flow of third grade fluid with slip boundary condition

2020 ◽  
Vol 75 (7) ◽  
pp. 649-655
Author(s):  
Juan Song ◽  
Shaowei Wang ◽  
Moli Zhao ◽  
Ning Li
Keyword(s):  
Boundary Condition ◽  
Velocity Profile ◽  
Slip Boundary Condition ◽  
Third Grade ◽  
Parallel Plates ◽  
Third Grade Fluid ◽  
Osmotic Flow ◽  
Slip Boundary ◽  
Grade Fluid ◽  
Electro Osmotic Flow

AbstractConsidering the slip boundary condition, the rotating electro-osmotic flow of a third grade fluid in a channel formed by two parallel plates is investigated in the present study. The charge distribution is treated with the Debye–Hückel approximation analytically. Based on the finite difference method, the velocity profile for rotating electro-osmotic flow of third grade fluid is obtained numerically. It is shown that the non-Newtonian parameter of third grade fluid and the velocity slip factor play the important roles for the rotating electro-osmotic flow. The increasing non-Newtonian parameter slows down the flow and decreases the velocity magnitude, and the increasing slip parameter β has the similar influence on the velocity profile. Furthermore, the effect of the inclusion of third grade on the velocity profile is more conspicuous in the area near the walls.

A Novel Mechanism for Heat Transfer Enhancement Through Microchannels Using Electrokinetic Effect

2005 ◽  
Author(s):  
Azad Qazi Zade ◽  
Reza Monazami ◽  
Mehrdad T. Manzari ◽  
Vahid Bazargan
Keyword(s):  
Heat Transfer ◽  
Velocity Profile ◽  
Heat Transfer Enhancement ◽  
Body Force ◽  
Three Dimensional ◽  
Transfer Enhancement ◽  
Electrokinetic Effect ◽  
Electroosmotic Pumping ◽  
Pressure Driven Flow ◽  
Pressure Driven

In this paper a three-dimensional numerical model is developed in order to study the heat transfer enhancement in rectangular microchannels due to electrokinetic effect. The electrokinetic body force on fluid elements gives some superior convective transport properties to the flow relative to pure pressure driven flow in microchannels. Unlike the conventional parabolic velocity profile of pressure driven laminar flow, the electrokinetic body force transforms the velocity profile to a slug-like flow. Due to sharp velocity gradient near the wall, the convective heat transfer properties of the flow are improved dramatically. Net charge distribution across the channel is obtained by solving the 2D Poisson-Boltzmann equation. The incompressible laminar Navier-Stokes equations are then solved numerically by considering the presence of electrokinetic body force using the finite element method. Finally to obtain the temperature field through the channel, three-dimensional energy equation is solved for constant wall temperature condition. The analysis provides a unique fundamental insight into the complex flow and heat transfer pattern established in the channel due to combined pressure driven-electroosmotic pumping mechanism. The results are compared with the pressure driven flow in same channel. The comparison reveals significant change in flow pattern and heat transfer characteristics of single phase flow through microchannel by adding electroosmotic pumping mechanism to pressure driven flow.

scholarly journals Temperature rise in a verging annular die

2016 ◽  
Vol 36 (7) ◽  
pp. 735-750 ◽  
Author(s):  
Georges R. Younes ◽  
A. Jeffrey Giacomin ◽  
Peter H. Gilbert
Keyword(s):  
Analytical Solution ◽  
Velocity Profile ◽  
Temperature Rise ◽  
Pressure Profile ◽  
Viscous Heating ◽  
Maximum Throughput ◽  
Flow Through ◽  
Pressure Driven Flow ◽  
Analytical Expressions ◽  
Pressure Driven

AbstractPlastic pipes, tubes or catheters are extruded by pressure-driven flows through annular dies. Whereas die lands are straight, the section connecting the die land to the extruder either converges or diverges, converging when the product is smaller than the extruder barrel, and diverging when larger. In this paper, we carefully consider the converging or diverging connecting flows, in spherical coordinates, for the most common configuration: the Newtonian pressure-driven flow through the annulus between two coapical coaxial cones. We derive theexactanalytical solution for the velocity profile, and then use this to arrive at theexactanalytical solution for the temperature rise caused by viscous heating. We care about this rise because it often governs maximum throughput, since pipe makers must protect the melt from thermal degradation. We find that both the velocity profile, and the temperature profile, peak over the same conical surface and this surface is nearer the inner die wall. We also provide analytical expressions for the nonlinear pressure profile and the die cooling requirement. We find that this cooling requirement is always higher on the inner cone.

Thermohydraulic Behavior of Minichannel Surface Simulated With Gaussian Function and Actual Roughness Data Generated Using Three-Dimensional Optical Surface Profilometer

2020 ◽  
Vol 142 (10) ◽  
Author(s):  
Indrasis Mitra ◽  
Indranil Ghosh
Keyword(s):  
Heat Transfer ◽  
Surface Roughness ◽  
Nusselt Number ◽  
Rough Surface ◽  
Gaussian Function ◽  
Three Dimensional ◽  
Optical Surface ◽  
Flow Perturbation ◽  
Smooth Channel ◽  
Effect Of Surface

Abstract The effect of surface roughness on the thermohydraulics in minichannels has been studied numerically. Fluid flow (at low Reynolds number) through a typical three-dimensional (3D) channel subjected to constant heat flux (at the bottom) is analyzed incorporating surface roughness on the solid–fluid interfaces characterized by its true random and nonperiodic nature. Two different approaches are adopted to model the rough channel surfaces. Topographic measurements have been performed on a stainless steel minichannel using an optical surface profilometer (OSP) to generate digital replica of the rough surface. Alternatively, the Gaussian function defined by two statistical parameters, namely average roughness (Ra) and correlation length (Cl), are employed to imitate the random nature of rough interface. At the outset, conjugate heat transfer simulations have been performed on the rough channel models and the results are validated against the experimental data. Finally, the effect of surface roughness on both local and global nondimensional performance parameters is analyzed and compared with findings from simulations performed on a similar smooth channel. The outcomes reveal an enhanced friction factor for flow over a rough surface, attributable to the near wall shear rate fluctuations experienced by the flow. Unlike smooth channels, the local Nusselt number (Nuy) exhibits continuous fluctuations along the channel axial length. The fully developed (Nufd) and the average (Nu¯) counterparts of the Nusselt number show enhanced magnitudes when compared to the theoretical predictions of the same in a smooth surface channel. This amplification can be attributed to two simultaneously acting factors: augmentation in heat transfer area and chaotic mixing due to flow perturbation. The magnitude of enhancement in terms of fully developed Nusselt number (Nufd) is roughly 1.3 times of its corresponding value in a smooth channel and the factor remains invariant of the supplied heat.

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