Enhancement of Mixing in a Microchannel by Using AC-Electroosmotic Effect

2008 ◽  
Author(s):  
Yangyang Wang ◽  
Sangmo Kang ◽  
Yongkweon Suh
Keyword(s):  
Numerical Simulations ◽  
Chaotic Behavior ◽  
Electrode Array ◽  
Longitudinal Direction ◽  
Central Line ◽  
Transverse Flow ◽  
Electrode Pair ◽  
Mixing Performance ◽  
Commercial Code ◽  
Micro Mixer

This study has focused on optimizing the AC-electroosmotic micro-mixer, which is composed of a microchannel with an array of rectangular electrodes attached on the bottom wall. The electrode array is spatial-periodically arranged in pairs symmetric with respect to the longitudinal central line. An AC electrode field is applied to the electrodes, which drives the secondary transverse flow in a circulating cell mode near the electrodes. The main flow along the channel longitudinal direction plus this secondary transverse flow contribute to the stretching and folding of the fluid flow, that is the chaotic behavior, and thus to the enhancement of the fluid mixing. To design the better micro-mixer, numerical simulations have been performed by using a commercial code (CFX 10). In the simulations, the concept of mixing index is employed to evaluate the mixing performance as well as to optimize the size and spacing of each electrode in one pair. It is found that the optimum design of one electrode pair, which leads to the best mixing performance, is not simply harmonic one. When the length ratio of the two electrodes in a pair closes to 2:1, the best mixing effect can be attained. The flow pattern was visualized. Furthermore, the velocity field will be measured with a PTV technique to validate the numerical simulations.

scholarly journals Asymmetrical Induced Charge Electroosmotic Flow on a Herringbone Floating Electrode and Its Application in a Micromixer

Micromachines ◽  
2018 ◽  
Vol 9 (8) ◽  
pp. 391 ◽  
Author(s):  
Qingming Hu ◽  
Jianhua Guo ◽  
Zhongliang Cao ◽  
Hongyuan Jiang
Keyword(s):  
Electrode Surface ◽  
Slip Velocity ◽  
Fluid Velocity ◽  
Laminar Flows ◽  
Fluid Mixing ◽  
Electrode Pair ◽  
Great Opportunity ◽  
Mixing Performance ◽  
Induced Charge ◽  
Floating Electrode

Enhancing mixing is of significant importance in microfluidic devices characterized by laminar flows and low Reynolds numbers. An asymmetrical induced charge electroosmotic (ICEO) vortex pair generated on the herringbone floating electrode can disturb the interface of two-phase fluids and deliver the fluid transversely, which could be exploited to accomplish fluid mixing between two neighbouring fluids in a microscale system. Herein we present a micromixer based on an asymmetrical ICEO flow induced above the herringbone floating electrode array surface. We investigate the average transverse ICEO slip velocity on the Ridge/Vee/herringbone floating electrode and find that the microvortex generated on the herringbone electrode surface has good potential for mixing the miscible liquids in microfluidic systems. In addition, we explore the effect of applied frequencies and bulk conductivity on the slip velocity above the herringbone floating electrode surface. The high dependence of mixing performance on the floating electrode pair numbers is analysed simultaneously. Finally, we investigate systematically voltage intensity, applied frequencies, inlet fluid velocity and liquid conductivity on the mixing performance of the proposed device. The microfluidic micromixer put forward herein offers great opportunity for fluid mixing in the field of micro total analysis systems.

Numerical and Experimental Analyses of Free and Forced Vibration of Thin-Walled Beams

2020 ◽  
pp. 2150018
Author(s):  
Wassim Jrad ◽  
Foudil Mohri ◽  
Guillaume Robin ◽  
El Mostafa Daya
Keyword(s):  
Numerical Simulations ◽  
Present Model ◽  
Natural Frequencies ◽  
Response Spectra ◽  
Test Results ◽  
The Finite Element Method ◽  
Coupled Modes ◽  
Free And Forced Vibrations ◽  
Commercial Code ◽  
Thin Walled

The flexural–torsional vibration behavior of unrestrained and braced thin-walled beams is investigated by experimental and finite elements approaches. In the experimental part, tests in free and forced vibrations of thin walled beams with arbitrary sections are analyzed. By the help of an instrumental hammer test and a shaker machine, the natural frequencies and the response spectra of the beams are extracted in the range 1–400[Formula: see text]Hz. Beam displacements are measured by some accelerometer transducers. The behavior is also investigated by the finite element method. In mesh process, 3D beams are adopted and an additional DOF is affected to the warping. The model is implemented in a home-made model. The numerical and experimental results are compared to numerical simulations of a commercial code. Test results and numerical simulations of the present model agree well. The model seems to be accurate especially in the presence of higher vibration and coupled modes.

Performance Evaluation of a Triangular-Prism-Slit Electrode Pair as an Electro-Conjugate Fluid Jet Generator

2011 ◽  
Author(s):  
Hai-bo Wang ◽  
Joon-wan Kim ◽  
Shinichi Yokota ◽  
Kazuya Edamura
Keyword(s):  
High Performance ◽  
Electrode Array ◽  
Research Field ◽  
Electrode Pair ◽  
Triangular Prism ◽  
Electrode Structure ◽  
Electrode Gap ◽  
Promising Candidate ◽  
Output Pressure ◽  
The Relationship

Electro-conjugate fluid (ECF) is a dielectric and functional fluid, which generates a powerful jet when electrodes inserted into it are subjected to a constant voltage of less than one thousand volts. As one essential research field on ECF, researchers have been conducting the study on electrodes. Several structures, e.g. planar parallel rod-like electrode array, ring-needle electrode pair and triangular-prism-slit (TPS) electrode pair, were proposed. Among them, the TPS electrode structure is often thought as the most promising candidate for future ECF applications thanks to its great merits of combining easy fabrication and relatively high performance. In this paper, in order to evaluate performance of the TPS electrode pair, a novel modular ECF-jet generator capable of independently adjusting alignment and gap of each electrode is designed. By utilizing it, the relationship between output pressure and parameters of the TPS electrode pair, including thickness, slit width, tip angle, electrode gap and alignment, are obtained.

Numerical Modeling of Spiral Micro-Mixers

2009 ◽  
Vol 74 ◽  
pp. 327-330
Author(s):  
Yong Jun Wee ◽  
Ai Qun Liu ◽  
Ren Jian Gan
Keyword(s):  
Numerical Modeling ◽  
Particle Separation ◽  
General Purpose ◽  
Mixing Process ◽  
Robust Solution ◽  
Mixing Performance ◽  
Multiple Phase ◽  
Mixer Design ◽  
Continuous Particle ◽  
Micro Mixer

Optimization of micro-mixing components is vital for efficient micro-electromechanical systems (MEMS) and lab-on-a-chips. In this area, it is ideal to have a universal micro-mixer design for general purpose multiple-phase fluidic mixing. Numerical methods to compute and analyze the mixing process in the spiral micro-mixer design are presented. This spiral design has also been found to be efficient for intra-droplet mixing as well as continuous particle separation by utilizing its attributing Dean flows. Analysis on the mixing performance of this design serves to present Archimedes’ spiral as a robust solution and exemplifies the effects of minute yet effective alterations to the design.

scholarly journals Aerodynamic Study of a Tricycle Wheel Subsystem for Drag Reduction

2012 ◽  
Author(s):  
Thomas Driant ◽  
Lakhdar Remaki ◽  
Stéphane Moreau ◽  
Alain Desrochers ◽  
Hachimi Fellouah
Keyword(s):  
Wind Tunnel ◽  
Drag Reduction ◽  
Numerical Simulations ◽  
Experimental Results ◽  
Flow Conditions ◽  
Commercial Code ◽  
Drag Analysis

This paper deals with a CFD and experimental drag analysis on an isolated rotating wheel subsystem (including its accessories: tire, suspension, A-arms and fender) of a tricycle vehicle. The main goal of the present work is to study the effect of the fender on the wheel subsystem drag and its optimization. The Star CCM+ commercial code was used for the numerical simulations. Different flow conditions were simulated and some results were validated by comparison to wind tunnel experimental results. To perform drag optimization, several aerodynamic fender shapes were designed and simulated as part of the subsystem. A drastic drag reduction up to 30.6% compared to the original wheel subsystem was achieved through numerical simulations.

scholarly journals Mixing Performance of a Passive Micro-Mixer with Mixing Units Stacked in Cross Flow Direction

Micromachines ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1530
Author(s):  
Makhsuda Juraeva ◽  
Dong-Jin Kang
Keyword(s):  
Numerical Study ◽  
Volume Flow Rate ◽  
Flow Direction ◽  
Cross Flow ◽  
Reynolds Numbers ◽  
High Concentration ◽  
Mixing Performance ◽  
Wall Impingement ◽  
The Cross ◽  
Micro Mixer

A new passive micro-mixer with mixing units stacked in the cross flow direction was proposed, and its performance was evaluated numerically. The present micro-mixer consisted of eight mixing units. Each mixing unit had four baffles, and they were arranged alternatively in the cross flow and transverse direction. The mixing units were stacked in four different ways: one step, two step, four step, and eight step stacking. A numerical study was carried out for the Reynolds numbers from 0.5 to 50. The corresponding volume flow rate ranged from 6.33 μL/min to 633 μL/min. The mixing performance was analyzed in terms of the degree of mixing (DOM) and relative mixing energy cost (MEC). The numerical results showed a noticeable enhancement of the mixing performance compared with other micromixers. The mixing enhancement was achieved by two flow characteristics: baffle wall impingement by a stream of high concentration and swirl motion within the mixing unit. The baffle wall impingement by a stream of high concentration was observed throughout all Reynolds numbers. The swirl motion inside the mixing unit was observed in the cross flow direction, and became significant as the Reynolds number increased to larger than about five. The eight step stacking showed the best performance for Reynolds numbers larger than about two, while the two step stacking was better for Reynolds numbers less than about two.

scholarly journals MEMS Impedance Biosensor for accurate and rapid detection of E.coli 0157:H7

2016 ◽  
Author(s):  
◽  
Shibajyoti Ghosh Dastider
Keyword(s):  
Electrode Array ◽  
Electrode Pair ◽  
Impedance Change ◽  
Bacterial Cells ◽  
Electrode Arrays ◽  
Measurement Sensitivity ◽  
Functional Region ◽  
Bulk Fluid ◽  
Treatment Techniques ◽  
Previous Design

Two Impedance biosensors based on interdigitated electrode (IDE) arrays were designed, fabricated and tested for detection of low concentration Escherichia coli O157:H7. The first biosensor consists of two set of gold IDE arrays embedded in a SU8-PDMS microchannel. Positive dielectrophoresis (p-DEP) is used to focus and concentrate the E.coli cells into the centre of the microchannel, using the first IDE array. The concentrated cells are then guided towards the sensing region microchannel, which has one-third the width of the initial microchannel. The bulk fluid keeps flowing toward the outer channel towards the waste outlets. The second IDE array located in the sensing region is used for impedimetric detection of the E.coli cells. A combination of standard photolithography, wet etching and plasma treatment techniques were used to fabricate the biosensor. The E.coli cells in the test solution were focused into the centre of the channel when excitation signal of 5 Vp-p at 5.6 MHz was applied across the electrode arrays. Before injecting the E.coli cells, polyclonal anti-E.coli antibodies were non-specifically immobilized on the sensing electrode array. This ensures specific detection of E.coli O157:H7 bacterial cells. As the concentrated E.coli cells (antigen) reach the sensing electrode array, they bind to the immobilized antibody sites. This antigen-antibody binding causes a change in the impedance which is measured using an impedance analyzer. The device performance was tested by measuring the impedance, between 100 Hz-1 MHz frequency, before and after applying p-DEP on the focusing electrode array, and after applying p-DEP on both the focusing and sensing electrodes. The result shows clearly that the use of p-DEP on the focusing IDE array significantly increased the measurement sensitivity with the lower detection limit being 3x10^2 CFU/mL. In addition, the use of p-DEP on both electrode arrays increased the measurement sensitivity by a factor of 2.9 to 4.5 times depending on the concentration. The second biosensor consists of a redesigned focusing region and multielectrode sensing region to improve the efficiency and to be able to detect even lower concentration E.coli O157:H7. Similar to the previous design this biosensor also consists of two functional region: focusing and sensing region. In this design, the focusing region consists a ramp down vertical electrode pair made of electroplated gold along with tilted (45 degree) thin film finger pairs, embedded in a microchannel. This configuration improves the concentration and focusing of the bacteria into the center of the microchannel, and direct them towards the sensing region. The sensing region consists of three IDE arrays, with varying number of electrode fingers (30, 20 and 10 pairs respectively), all embedded inside a narrow microchannel and functionalized using anti-E.coli antibody. As E.coli binds to the antibody, it results in impedance change. The biosensor was fabricated on a glass substrate using SU8 negative photoresist to form the microchannel, gold electroplating to form the vertical focusing electrode pair, thin gold film to form the detection electrode, the finger electrodes, traces and bonding pads, and PDMS to seal the device. This biosensor was able to detect concentrations as low as 39 CFU/mL, which indicates a 7.5 times higher sensitivity, over the previous design.

Study of Mixing Characteristics Over a Spacer Grid With Sloping Channels Based on Numerical Simulations in a PWR 5×5 Rod Bundle Using CFD Codes

2013 ◽  
Author(s):  
Xi Chen ◽  
Hong Zhang
Keyword(s):  
Numerical Simulations ◽  
Safety Margin ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Spacer Grid ◽  
Pressurized Water ◽  
Spacer Grids ◽  
Rod Bundle ◽  
Commercial Code ◽  
Water Reactors

Spacer grids are important components of fuel assemblies for Pressurized Water Reactors (PWR). The presence of spacer grid promotes local heat transfer adjacent to the rod wall downstream by inducing swirl and cross flows within and between sub-channels to increase thermal hydraulic safety margin. Recent years, Computational Fluid Dynamics (CFD) methodologies are widely adopted to designs of spacer grids. This paper presents results of numerical simulations with commercial code CFX 12.0 in a PWR 5 × 5 rod bundle including a spacer grid with sloping channels. Based on a combined mesh generation approach of structured and unstructured mesh, distributions of velocity fields, temperature and pressure fields downstream the spacer grid were analyzed. The results indicate that cross flows caused by the spacer grid are uniform in circumference inducing no thermal hydraulic deterioration, but mass exchange between central hot fluid and external cold fluid appears insufficient for the new style grid.

scholarly journals Investigation on a Novel Support System for Automatic Ship Berthing in Marine Practice

2019 ◽  
Vol 7 (4) ◽  
pp. 114 ◽  
Author(s):  
Van Suong Nguyen
Keyword(s):  
Numerical Simulations ◽  
Support System ◽  
Longitudinal Direction ◽  
Superior Performance ◽  
Generalization Capability ◽  
Fuzzy Controllers ◽  
Ship Berthing

For safe ship berthing, all steps involved, from bringing the ship to the fairway area to directing it to the final wharf position at a desirable speed, need to be performed properly. In this article, a support system is proposed to automatically bring the ship into the berth after completing the maneuvering process. This proposed system requires no involvement of a shipmaster, enabling automatic ship berthing in marine practice. Three fuzzy controllers are proposed to conduct different tasks of berthing. The first controller is designed to control the movement of the ship in a longitudinal direction towards the wharf while the second controller stabilizes the relative bearing error with respect to the tugboat. The final controller is responsible for bringing the ship into a wharf according to crabbing motion with bow thruster and tugboat simultaneously. Compared to other approaches, ours has a wider range of adoption, better generalization capability, and is more suitable for marine practice. Comprehensive experiments in numerical simulations are carried out, showing the superior performance of the proposed support system for automatic ship berthing.

Longitudinal and circumferential spike patches in the canine small intestine in vivo

2003 ◽  
Vol 285 (5) ◽  
pp. G1014-G1027 ◽  
Author(s):  
Wim J. E. P. Lammers ◽  
Luc Ver Donck ◽  
Jan A. J. Schuurkes ◽  
Betty Stephen
Keyword(s):  
Small Intestine ◽  
Slow Wave ◽  
Electrode Array ◽  
Longitudinal Direction ◽  
Canine Model ◽  
Interelectrode Distance ◽  
Intestinal Tube ◽  
Antimesenteric Border ◽  
Local Patterns

In an open-abdominal anesthetized and fasted canine model of the intact small intestine, the presence, location, shape, and frequency of spike patches were investigated. Recordings were performed with a 240-electrode array (24 × 10, 2-mm interelectrode distance) from several sites sequentially, spanning the whole length of the small intestine. All 240 electrograms were recorded simultaneously during periods of 5 min and were analyzed to reconstruct the origin and propagation of individual spikes. At every level in the small intestine, spikes propagated in all directions before stopping abruptly, thereby activating a circumscribed area termed a “patch.” Two types of spikes were found: longitudinal spikes, which propagated predominantly in the longitudinal direction and occurred most often in the duodenum, and a second type, circumferential spikes, which propagated predominantly in the circular direction and occurred much more frequently in the jejunum and ileum. Circumferential spikes conducted faster than longitudinal spikes (17 ± 6 and 7 ± 2 cm/s, respectively; P < 0.001). Circumferential spikes originated in >90% of all cases from the antimesenteric border, whereas longitudinal spikes were initiated all around the circumference of the intestinal tube. Finally, the spatial sequence of spike patches after the slow wave was very irregular in the upper part of the intestine but much more regular in the lower part. In conclusion, spikes and spike patches occur throughout the small intestine, whereas their type, sites of origin, extent of propagation, and frequencies of occurrence differ along the length of the small intestine, suggesting differences in local patterns of motility.

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