scholarly journals A numerical investigation into electroosmotic flow in microchannels with complex wavy surfaces

2011 ◽  
Vol 15 (suppl. 1) ◽  
pp. 87-94 ◽  
Author(s):  
Her-Terng Yau ◽  
Cheng-Chi Wang ◽  
Ching-Chang Cho ◽  
Cha’o-Kuang Chen
Keyword(s):  
Cross Sections ◽  
Electroosmotic Flow ◽  
Flow Characteristics ◽  
Velocity Profiles ◽  
Governing Equations ◽  
Electrical Field ◽  
Flow Recirculation ◽  
Wavy Surfaces ◽  
Pressure Driven Flow ◽  
General Method

This study investigates the flow characteristics of electroosmotic flow in a microchannel with complex wavy surfaces. A general method of coordinate transformation is used to solve the governing equations describing the electroosmotic flow in the microchannel. Numerical simulations are performed to analyze the effects of wave amplitude on the electrical field, flow streamlines, and flow fields in the microchannel. The simulation results show that, compared to a traditional pressure-driven flow, flow recirculation is not developed in the electroosmotic flow in a microchannel with complex wavy surfaces. The simulations also show that the electrical field and velocity profiles change along the channel in the region of wavy surfaces. Non-flat velocity profiles are observed in different cross-sections of the channel in the region of wavy surfaces.

Characteristics of Transient Electroosmotic Flow in Microchannels With Complex-Wavy Surface and Periodic Time-Varying Electric Field

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
Ching-Chang Cho ◽  
Chieh-Li Chen ◽  
Cha'o-Kuang Chen
Keyword(s):  
Electric Field ◽  
Strouhal Number ◽  
Electric Potential ◽  
Electroosmotic Flow ◽  
Flow Characteristics ◽  
Threshold Value ◽  
Oscillation Period ◽  
Wavy Surface ◽  
Time Varying ◽  
Flow Recirculation

A numerical investigation is performed into the flow characteristics of the electroosmotic flow induced within a microchannel with a complex-wavy surface by a time-varying periodic electric field. The simulations focus specifically on the effects of the Strouhal number of the periodic electric potential, the amplitude of the periodic electric potential, the amplitude of the complex-wavy surface, and the waveform geometry. The results show that under steady-time periodic conditions, the flow pattern induced within the microchannel varies over the course of the oscillation period. In particular, it is shown that a flow recirculation structure is generated in the trough region of the wavy surface as the applied electric field falls to zero if the amplitude of the wavy surface exceeds a certain threshold value. In addition, it is shown that the phases of the electric field and electroosmotic velocity near the wall surface are almost identical. However, a phase shift exists between the electric field and the bulk flow velocity in the central region of the channel; particularly at larger values of the Strouhal number. Finally, it is shown that the velocity profile near the wavy surface is more sensitive to changes in the waveform geometry than that in the center of the channel. Overall, the simulation results presented in the study provide a useful source of reference for the development of new microfluidic systems incorporating microchannels with complex-wavy surfaces.

scholarly journals Electro-osmotic driven flow of Eyring Powell nanofluid in an asymmetric channel

2021 ◽  
Author(s):  
Vijayaragavan R ◽  
Tamizharasi P ◽  
Magesh A
Keyword(s):  
Electroosmotic Flow ◽  
Numerical Study ◽  
Nonlinear Partial Differential Equations ◽  
Mathematical Software ◽  
Asymmetric Channel ◽  
Governing Equations ◽  
Electrical Field ◽  
Nano Fluid ◽  
Theory Approximation ◽  
Energy Equations

This article aims to investigate the numerical study of electroosmotic flow of the Eyring Powell fluid under the peristaltic mechanism with the influence of the porous medium in the micro-channel. The modified system is applied externally to an electrical field in the horizontal direction and to a magnetic field in the transverse direction. The flow of nanofluids is considered in the computation. The governing equations in the nano-fluid flow are modulated. Influence of lubrication theory approximation longequations are shortened. Reduced coupled nonlinear partial differential equations like velocity and energy equations are numerically solved using the powerful and well-known mathematical software MATHEMATICA by built in NDSolve command. The influence of various important parameters on the velocity and temperature profile is summarised by graphs.

scholarly journals Interactions between Tandem Cylinders in an Open Channel: Impact on Mean and Turbulent Flow Characteristics

Water ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 1718
Author(s):  
Hasan Zobeyer ◽  
Abul B. M. Baki ◽  
Saika Nowshin Nowrin
Keyword(s):  
Turbulent Flow ◽  
Open Channel ◽  
Recirculation Zone ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Flow Recirculation ◽  
Tandem Cylinders ◽  
Flow Development ◽  
The Mean ◽  
Recirculation Length

The flow hydrodynamics around a single cylinder differ significantly from the flow fields around two cylinders in a tandem or side-by-side arrangement. In this study, the experimental results on the mean and turbulence characteristics of flow generated by a pair of cylinders placed in tandem in an open-channel flume are presented. An acoustic Doppler velocimeter (ADV) was used to measure the instantaneous three-dimensional velocity components. This study investigated the effect of cylinder spacing at 3D, 6D, and 9D (center to center) distances on the mean and turbulent flow profiles and the distribution of near-bed shear stress behind the tandem cylinders in the plane of symmetry, where D is the cylinder diameter. The results revealed that the downstream cylinder influenced the flow development between cylinders (i.e., midstream) with 3D, 6D, and 9D spacing. However, the downstream cylinder controlled the flow recirculation length midstream for the 3D distance and showed zero interruption in the 6D and 9D distances. The peak of the turbulent metrics generally occurred near the end of the recirculation zone in all scenarios.

Fluid Flow Structure in Arterial Bypass Anastomosis

2005 ◽  
Vol 127 (4) ◽  
pp. 611-618 ◽  
Author(s):  
C. M. Su ◽  
D. Lee ◽  
R. Tran-Son-Tay ◽  
W. Shyy
Keyword(s):  
Fluid Flow ◽  
Flow Structure ◽  
Bypass Graft ◽  
Flow Characteristics ◽  
Navier Stokes ◽  
Complex Flow ◽  
Arterial Bypass ◽  
Flow Recirculation ◽  
Area Reduction ◽  
Complex Flow Structure

The fluid flow through a stenosed artery and its bypass graft in an anastomosis can substantially influence the outcome of bypass surgery. To help improve our understanding of this and related issues, the steady Navier-Stokes flows are computed in an idealized arterial bypass system with partially occluded host artery. Both the residual flow issued from the stenosis—which is potentially important at an earlier stage after grafting—and the complex flow structure induced by the bypass graft are investigated. Seven geometric models, including symmetric and asymmetric stenoses in the host artery, and two major aspects of the bypass system, namely, the effects of area reduction and stenosis asymmetry, are considered. By analyzing the flow characteristics in these configurations, it is found that (1) substantial area reduction leads to flow recirculation in both upstream and downstream of the stenosis and in the host artery near the toe, while diminishes the recirculation zone in the bypass graft near the bifurcation junction, (2) the asymmetry and position of the stenosis can affect the location and size of these recirculation zones, and (3) the curvature of the bypass graft can modify the fluid flow structure in the entire bypass system.

Investigations on Flow Characteristics in Diffuser-Discharge-Channel of Volute Casing

2018 ◽  
Author(s):  
Yandong Gu ◽  
Ji Pei ◽  
Shouqi Yuan ◽  
Jinfeng Zhang ◽  
Ernst Nikolajew ◽  
...  
Keyword(s):  
Cross Sections ◽  
Discharge Channel ◽  
Transient Flow ◽  
Pressure Fluctuations ◽  
Flow Characteristics ◽  
Centrifugal Pumps ◽  
Discharge Pipe ◽  
Hydraulic Design ◽  
Flow Loss ◽  
Two Sides

The volute casing used in centrifugal pumps is efficient for the transformation of kinetic energy into pressure energy, however, its asymmetric hydraulic design makes the flow in diffuser-discharge-channel (DDC) inhomogeneous, resulting in unsatisfactory flow patterns. In this study, the unsteady numerical simulations are carried out to investigate the transient flow characteristics in DDC. The accuracy of numerical results is found to agree well with experimental performance and pressure fluctuations. It is observed that the flow in DDC is significantly uneven. At the elbow of DDC, the static pressure on the volute left side (VL) is larger than the volute right side (VR) due to the flow impact and flow separation respectively. Thereby, this high-pressure gradient induces the secondary flow on the cross sections of DDC. Further, there is an obvious dependency of pressure fluctuations in the discharge pipe on the strong interaction between the impeller and tongue, in which four small peaks and four large peaks can be observed. At each moment, the pressure on VL gradually decreases from the inlet of discharge pipe to the pump outlet, while it increases on VR, finally, two sides tend to be the same. The pressure fluctuation intensity gradually becomes equivalent-distributed. In particular, it should be noticed that the energy loss in the diffuser part is larger than the discharge pipe, which requires a redesign concerning hydraulic performance. This study can help to better understand the transient flow characteristics and provide guidance for reducing flow loss in the volute casing.

scholarly journals 3D Hydrodynamic Focusing in Microscale Optofluidic Channels Formed with a Single Sacrificial Layer

Micromachines ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 349 ◽  
Author(s):  
Erik S. Hamilton ◽  
Vahid Ganjalizadeh ◽  
Joel G. Wright ◽  
Holger Schmidt ◽  
Aaron R. Hawkins
Keyword(s):  
Cross Sections ◽  
Optical Waveguides ◽  
Sacrificial Layer ◽  
Three Dimensional ◽  
Single Layer ◽  
Detection Sensitivity ◽  
Low Flow ◽  
Hydrodynamic Focusing ◽  
Induced Focusing ◽  
Pressure Driven Flow

Optofluidic devices are capable of detecting single molecules, but greater sensitivity and specificity is desired through hydrodynamic focusing (HDF). Three-dimensional (3D) hydrodynamic focusing was implemented in 10-μm scale microchannel cross-sections made with a single sacrificial layer. HDF is achieved using buffer fluid to sheath the sample fluid, requiring four fluid ports to operate by pressure driven flow. A low-pressure chamber, or pit, formed by etching into a substrate, enables volumetric flow ratio-induced focusing at a low flow velocity. The single layer design simplifies surface micromachining and improves device yield by 1.56 times over previous work. The focusing design was integrated with optical waveguides and used in order to analyze fluorescent signals from beads in fluid flow. The implementation of the focusing scheme was found to narrow the distribution of bead velocity and fluorescent signal, giving rise to 33% more consistent signal. Reservoir effects were observed at low operational vacuum pressures and a balance between optofluidic signal variance and intensity was achieved. The implementation of the design in optofluidic sensors will enable higher detection sensitivity and sample specificity.

Simulation of Flow and Mass Transport in a Meander Microchannel Subject to Electroosmotic Pumping

2003 ◽  
Author(s):  
Dominik P. J. Barz ◽  
Peter Ehrhard
Keyword(s):  
Mass Transport ◽  
Double Layers ◽  
Complex Flow ◽  
Electrical Field ◽  
Electrical Fields ◽  
Electrical Double Layers ◽  
Electroosmotic Pumping ◽  
Pressure Driven Flow ◽  
Flow And Mass Transport ◽  
Pressure Driven

We have investigated the flow and mass transport within an electroosmotically-pumped incompressible liquid through a meander microchannel system. We employ two-dimensional, time-dependent Finite Element simulations in conjunction with a matched asymptotic treatment of the electrical double layers. The electroosmotic pumping is realized for two idealized and two realistic electrical fields, while a pressure-driven flow is used for comparison. We focus on the aspects of the electroosmotic transport. We find for most of the electroosmotically-driven cases rather complex flow fields, involving recirculation regions. These recirculation regions in all cases increase dispersion. (i) The least dispersion is associated with a plug-type velocity profile, which is obtained for an idealized purely wall-tangential orientation of the electrical field. (ii, iii) We find that both, the idealized horizontal electrical field and the real electrical field between two vertical plates give considerably higher dispersion than the pressure-driven flow. Vertical plate electrodes, therefore, do not allow for a electrical field, which minimizes dispersion. (iv) The arrangement of two point electrodes at the in and out sections likewise proves to be no optimal means to reduce dispersion beyond the pressure-driven flow. Thus, meander geometries of channels, in general, cause severe problems if electroosmotic pumping needs to be achieved in combination with minimized dispersion.

Viscoelectric Effect on the Electroosmotic Flow in Nanochannels With Heterogeneous Zeta Potentials

2018 ◽  
Author(s):  
Edson M. Jimenez ◽  
Federico Méndez ◽  
Juan P. Escandón
Keyword(s):  
Electroosmotic Flow ◽  
Fluid Velocity ◽  
Volumetric Flow Rate ◽  
Mass Conservation ◽  
Double Layers ◽  
Fluid Viscosity ◽  
Governing Equations ◽  
Flat Plates ◽  
Zeta Potentials ◽  
Poisson Boltzmann

In the present work, we realize a study about the influence of viscoelectric effect on the electroosmotic flow of Newtonian fluids in nanochannels formed by two parallel flat plates. In the problem, the channel walls have heterogeneous zeta potentials which follow a sinusoidal distribution; moreover, viscoelectric effects appear into the electric double layers when high zeta potentials are considered at the channel walls, modifying the fluid viscosity and the fluid velocity. To find the solution of flow field, the modified Poisson-Boltzmann, mass conservation and momentum governing equations, are solved numerically. In the results, combined effects from the zeta potential heterogeneities and viscosity changes yields different kind of flow recirculations controlled by the dephasing angle, amplitude and number of waves of the heterogeneities at the walls. The viscoelectric effect produces a decrease in the magnitude of velocity profiles and volumetric flow rate when the high zeta potentials are magnified. Additionally, the heterogeneous zeta potentials at the walls generate an induced pressure on the flow. This investigation extend the knowledge of electroosmotic flows under field effects for future mixing applications.

Sign in / Sign up

Export Citation Format

Share Document