Characterisation of Flow and Mass Transfer in Cross Shape and T-Shape Micromixers

2009 ◽  
Author(s):  
Nassim Ait Mouheb ◽  
Agnes Montillet ◽  
Camille Solliec ◽  
Jacques Comiti ◽  
Patrick Legentilhomme ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Reynolds Number ◽  
Biomedical Applications ◽  
Particle Image ◽  
Three Dimensional ◽  
Flow Conditions ◽  
Image Velocimetry ◽  
Mixing Quality ◽  
Physical Phenomena ◽  
Cross Type

The understanding of physical phenomena such as flow behaviour and mass transfer performance is needed in order to develop appropriate micromixers for industrial or biomedical applications. In this work, CFD is used to characterize the flow and the liquid mixing quality in a micromixer as a function of the Reynolds number. Two micromixers are studied in steady flow conditions; they are based on two geometries, respectively T-shaped (⊤) and cross-type (+). Simulations allow, in the case of ⊤ micromixers, to chart the topology of the flow and to describe the evolution of species concentration downstream the crossing. The streamlines layout and the mixing quality curves reveal three characteristic types of flow previously reported in the literature, depending on Reynolds number: stratified, vortex and engulfment flows. In the case of cross-type micromixers, the structure of the flow is strongly three-dimensional and is characterized by symmetrical vortices in both output channels. The results show that the + shaped system can improve the mixing process in comparison with the micromixers having ⊤ geometry. The second part of the study is experimental. Two cells are constructed, for both geometries (T-shaped and cross) using square channels with 400 μm hydraulic diameter. In order to use particle image velocimetry (PIV), a system has been adapted to measure velocity fields for various channel plans at different channel depths. This allows observing the evolution of the flow and the vortices development along the microchannels. A second experimental technique, the electrochemical one involving microelectrodes implemented at several positions on the channel wall located near the crossing, has been used. The electrochemical method can locally characterize the formation of swirling flows. These two complementary experimental results will be analysed and a comparison with the CFD results will be performed.

Numerical Study of the Flow and Mass Transfer in Micromixers

2008 ◽  
Author(s):  
Nassim Ait Mouheb ◽  
Camille Solliec ◽  
Agnes Montillet ◽  
Jacques Comiti ◽  
Patrick Legentilhomme ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Reynolds Number ◽  
Numerical Study ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Experimental Point ◽  
Shear Stresses ◽  
Dynamic Simulations ◽  
Mixing Quality ◽  
Cross Type

Computational fluid dynamic simulations are used to characterize the flow and the liquid mixing quality in a micromixer as a function of the Reynolds number. Two micromixers are studied in steady flow conditions; they are based on two geometries, respectively T-shaped and cross-type (⊤ and + shapes). Simulations allow, in the case of ⊤ micromixers, to chart the topology of the flow and to describe the evolution of species concentration downstream the intersection. The streamline layout and the mixing quality curves reveal the three characteristic types of flow, depending on Reynolds number: stratified, vortex and engulfment flows. Vortices appear after impingement, in the exit channel. They become asymmetrical and gain in length with an increase in Re making the flow unsteady, which induces an enhancement of the mass transfer by advection between the two liquids. In the case of cross-type micromixers, the structure of the flow is strongly three-dimensional. It is characterized by symmetrical vortices in both output channels. In the zone close to the impingement, a back flow is observed which induces strong shear stresses. The results show that the + shaped system can improve the mixing process in comparison with the micromixers having ⊤ geometry. The numerical study also allows to select the locations of the most relevant zones of study, from an experimental point of view. It will allow to choose the location of PIV planes and local non intrusive sensors, such as electrochemical microprobes, in order to experimentally investigate the flow.

Water Synthetic Jet Driven by a Piezoelectric Actuator – LIF and PIV Experiments

2015 ◽  
Vol 1104 ◽  
pp. 45-50 ◽  
Author(s):  
Zuzana Broučková ◽  
Shu Shen Hsu ◽  
An Bang Wang ◽  
Zdeněk Trávníček
Keyword(s):  
Reynolds Number ◽  
Particle Image Velocimetry ◽  
Piezoelectric Actuator ◽  
Particle Image ◽  
Three Dimensional ◽  
Laser Induced Fluorescence ◽  
Synthetic Jet ◽  
Fluid Exchange ◽  
Image Velocimetry ◽  
Surrounding Fluid

A synthetic jet (SJ) is a fluid jet flow generated from fluid oscillations during a periodical fluid exchange between an actuator cavity and surrounding fluid. A water synthetic jet was generated from submerged piezoelectric-driven SJ actuator. The actuator slot width was 0.36 mm. The experiments were performed using laser induced fluorescence (LIF) flow visualization and particle image velocimetry (PIV) techniques, both in a phase locked setup. The LIF visualization was used to demonstrate three-dimensional nature of the SJ formation process and to estimate SJ velocity. The PIV experiment quantified SJ velocity cycles in chosen plans. The driven frequency was adjusted near the resonance at approximately 46 Hz. It was evaluated theoretically and confirmed experimentally by means of LIF visualization. The time-mean orifice velocity and the Reynolds number were estimated asU0= 0.07–0.10 m/s andRe= 100–150, respectively.

Dynamics of laminar separation bubbles at low-Reynolds-number aerofoils

2009 ◽  
Vol 630 ◽  
pp. 129-153 ◽  
Author(s):  
R. HAIN ◽  
C. J. KÄHLER ◽  
R. RADESPIEL
Keyword(s):  
Reynolds Number ◽  
Particle Image ◽  
Separation Bubble ◽  
Three Dimensional ◽  
Transition Process ◽  
Spanwise Direction ◽  
Time Resolved ◽  
Laminar Separation ◽  
Image Velocimetry ◽  
Dominant Frequencies

The laminar separation bubble on an SD7003 aerofoil at a Reynolds numberRe= 66000 was investigated to determine the dominant frequencies of the transition process and the flapping of the bubble. The measurements were performed with a high-resolution time-resolved particle image velocimetry (TR-PIV) system. Contrary to typical measurements performed through conventional PIV, the different modes can be identified by applying TR-PIV. The interaction between the shed vortices is analysed, and their significance for the production of turbulence is presented. In the shear layer above the bubble the generation and amplification of vortices due to Kelvin–Helmholtz instabilities is observed. It is found that these instabilities have a weak coherence in the spanwise direction. In a later stage of transition these vortices lead to a three-dimensional breakdown to turbulence.

PIV MEASUREMENTS AND NUMERICAL VALIDATION OF END-TO-SIDE ANASTOMOSIS

2010 ◽  
Vol 10 (01) ◽  
pp. 123-138 ◽  
Author(s):  
AMAL OWIDA ◽  
HUNG DO ◽  
WILLIAM YANG ◽  
YOS S. MORSI
Keyword(s):  
Particle Image ◽  
Three Dimensional ◽  
Quantitative Information ◽  
Velocity Fields ◽  
Flow Conditions ◽  
Ansys Software ◽  
Piv Measurements ◽  
Piv Technique ◽  
Image Velocimetry ◽  
Glass Model

In this article, particle image velocimetry (PIV) technique was used to determine the instantaneous velocity fields inside a model of end-to-side anastomosis under various physiological flow conditions. Using ANSYS software, a three-dimensional (3D) computational model at the peak systolic blood flow was simulated. The numerical and experimental results were presented and discussed in terms of velocity fields at various locations along the graft and the host artery. The numerical results were then compared with the experimental data and a large difference was found, which was attributed to the imperfection of manufacturing the glass model and measurements error associated with PIV. The findings indicated in general that the analysis at peak systole, steady flow could help in providing essential quantitative information of the hemodynamics in anastomotic artery.

A particle image velocimetry study on the pulsatile flow characteristics in straight tubes with an asymmetric bulge

2000 ◽  
Vol 214 (5) ◽  
pp. 655-671 ◽  
Author(s):  
S C M Yu ◽  
J B Zhao
Keyword(s):  
Particle Image Velocimetry ◽  
Steady Flow ◽  
Pulsatile Flow ◽  
Flow Condition ◽  
Particle Image ◽  
Flow Characteristics ◽  
Reynolds Numbers ◽  
Working Fluid ◽  
Flow Conditions ◽  
Image Velocimetry

Flow characteristics in straight tubes with an asymmetric bulge have been investigated using particle image velocimetry (PIV) over a range of Reynolds numbers from 600 to 1200 and at a Womersley number of 22. A mixture of glycerine and water (approximately 40:60 by volume) was used as the working fluid. The study was carried out because of their relevance in some aspects of physiological flows, such as arterial flow through a sidewall aneurysm. Results for both steady and pulsatile flow conditions were obtained. It was found that at a steady flow condition, a weak recirculating vortex formed inside the bulge. The recirculation became stronger at higher Reynolds numbers but weaker at larger bulge sizes. The centre of the vortex was located close to the distal neck. At pulsatile flow conditions, the vortex appeared and disappeared at different phases of the cycle, and the sequence was only punctuated by strong forward flow behaviour (near the peak flow condition). In particular, strong flow interactions between the parent tube and the bulge were observed during the deceleration phase. Stents and springs were used to dampen the flow movement inside the bulge. It was found that the recirculation vortex could be eliminated completely in steady flow conditions using both devices. However, under pulsatile flow conditions, flow velocities inside the bulge could not be suppressed completely by both devices, but could be reduced by more than 80 per cent.

A Method for Measuring Deformation Rates in Hydrogel Structures: Multi-Plane Imaging and Measurement Limitations

2000 ◽  
Author(s):  
Joseph M. Bauer ◽  
David J. Beebe
Keyword(s):  
Cross Sections ◽  
Particle Image ◽  
Three Dimensional ◽  
Local Deformation ◽  
Dimensional Representation ◽  
Volume Changes ◽  
Mechanical Constraints ◽  
Seed Particles ◽  
Three Dimensional Representation ◽  
Image Velocimetry

Abstract A technique for determining the three dimensional motions of hydrogel structures in microchannels is introduced. In developing this technique, we have adapted microscopic particle image velocimetry (μPIV), a method for measuring velocity fields in microfluidic devices. The motions of 1 μm fluorescent seed particles that are incorporated into a hydrogel microstructure (200 μm tall × 400 μm diameter) are tracked over several expansion cycles using microscopy. Combining measurements taken in different planes produces a three-dimensional representation of the motions present during volume changes can be reconstructed. By providing cross sections of the local deformation rates in hydrogel microstructures, this technique allows for the optimization of device designs as well as providing a better understanding of the processes by which hydrogels change volume under mechanical constraints.

Measurement of Velocity Profiles of Laminar to Turbulent Water Flows in a Tube Using Particle Image Velocimetry

2004 ◽  
Author(s):  
Meredith R. Martin
Keyword(s):  
Reynolds Number ◽  
Particle Image Velocimetry ◽  
Particle Image ◽  
Glass Tube ◽  
Reynolds Numbers ◽  
Velocity Profiles ◽  
Reynolds Number Flow ◽  
Image Velocimetry ◽  
Dye Visualization ◽  
Number Flow

The transition from laminar to turbulent in-tube flow is studied in this paper. Water flow in a glass tube with an inside diameter of 21.7 mm was investigated by two methods. First, a dye visualization test using a setup similar to the 1883 experiment of Osborne Reynolds was conducted. For the dye visualization, Reynolds numbers ranging from approximately 1000 to 3500 were tested and the transition from laminar to turbulent flow was observed between Reynolds numbers of 2500 and 3500. For the second method, a particle image velocimetry (PIV) system was used to measure the velocity profiles of flow in the same glass tube at Reynolds numbers ranging from approximately 500 to 9000. The resulting velocity profiles were compared to theoretical laminar profiles and empirical turbulent power-law profiles. Good agreement was found between the lower Reynolds number flow and the laminar profile, and between the higher Reynolds number flow and turbulent power-law profile. In between the flow appeared to be in a transition region and deviated some between the two profiles.

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