Numerical Investigations of a Passive Micromixer Based on Minkowski Fractal Principle

2019 ◽  
Vol 18 (2) ◽  
Author(s):  
Yao Chen ◽  
Xueye Chen
Keyword(s):  
Pressure Drop ◽  
Flow Direction ◽  
Reynolds Numbers ◽  
Mixing Efficiency ◽  
Numerical Investigations ◽  
Two Fluids ◽  
Chaotic Convection ◽  
Passive Micromixer ◽  
Minkowski Fractal ◽  
Obstacle Height

Abstract This paper is mainly to study the mixing efficiency and pressure drop of the Minkowski fractal obstacle micromixers. The mixing efficiency of primary Minkowski fractal obstacle (PMFO) micromixer and secondary Minkowski fractal obstacle (SMFO) micromixer are compared at five kinds of Reynolds numbers. With the increase of obstacle height and the decrease of distance, the chaotic convection in the microchannel is enhanced. Especially at obstacle height (h) = 0.2 mm, obstacle distance (D) = 0.15 mm, and Re = 100, the vortex caused by the Minkowski fractal obstacle structure is more obvious. In addition, vortex phenomenon increases the contact area of two fluids and enhances chaotic convection. It shows that the flow direction of the fluid in the microchannel varies significantly.

Two Fluid Mixing in a Micromixer with Helical Channels and Grooved Surfaces

2013 ◽  
Vol 284-287 ◽  
pp. 2096-2101
Author(s):  
Ya Hui Hu ◽  
Farn Shiun Hwu ◽  
Kao Hui Lin
Keyword(s):  
Pure Water ◽  
Reynolds Numbers ◽  
Acetone Solution ◽  
Mixing Efficiency ◽  
Inspection Method ◽  
Two Fluids ◽  
Biomedical Diagnosis ◽  
Passive Micromixer ◽  
Image Inspection ◽  
Helical Channels

The mixing behavior of two fluids in a passive micromixer with a Y-type inlet and helical fluid channels with herringbone grooves etched into the bottom was studied in a numerical simulation and experiments. The mixing of the pure water and acetone solution prepared with different Reynolds numbers and acetone concentrations was investigated. An image inspection method using the variance in contrast of the image gray level as the measurement parameter was adopted to calculate the mixing efficiency distribution. Inspection results show that the mixing efficiency decreased with the increase in the concentration of the acetone solution, although the mixing efficiency around the outlet reached to a value of 90%, even when the Reynolds numbers of the fluids were as low as Re = 1, and the best efficiency achieved for the case of Re = 10 was over 98%. The results show that it should be possible to apply the proposed micromixer in the field of biomedical diagnosis.

A Planar Labyrinth Micromixer

2010 ◽  
Author(s):  
Jeremy T. Cogswell ◽  
Peng Li ◽  
Mohammad Faghri
Keyword(s):  
Soft Lithography ◽  
Lab On A Chip ◽  
Fluorescein Isothiocyanate ◽  
Reynolds Numbers ◽  
Mixing Efficiency ◽  
Mixing Length ◽  
Two Fluids ◽  
Curved Channels ◽  
Passive Mixing ◽  
Important Challenge

Rapid mixing of two fluids in microchannels has posed an important challenge to the development of many integrated lab-on-a-chip systems. In this paper, we present a planar labyrinth micromixer (PLM) to achieve rapid and passive mixing by taking advantage of a synergistic combination of the Dean vortices in curved channels, a series of perturbation to the fluids from the sharp turns, and an expansion and contraction of the flow field via a circular chamber. The PLM is constructed in a single soft lithography step and the labyrinth has a footprint of 7.32 mm × 7.32 mm. Experiments using fluorescein isothiocyanate solutions and deionized water demonstrate that the design achieves fast and uniform mixing within 9.8 s to 32 ms for Reynolds numbers between 2.5 and 30. Compared to the mixing in the prevalent serpentine design, our design results in 38% and 79% improvements on the mixing efficiency at Re = 5 and Re = 30 respectively. An inverse relationship between mixing length and mass transfer Pe´clet number (Pe) is observed, which is superior to the logarithmic dependence of mixing length on Pe in chaotic mixers. Having a simple planar structure, the PLM can be easily integrated into lab-on-a-chip devices where passive mixing is needed.

A NOVEL 3D MICROMIXER WITH QUARTIC KOCH CURVE FRACTAL

2021 ◽  
pp. 2150049
Author(s):  
SIYUE XIONG ◽  
XUEYE CHEN
Keyword(s):  
Numerical Simulation ◽  
Deflection Angle ◽  
Reynolds Numbers ◽  
Mixing Efficiency ◽  
Flow State ◽  
Koch Curve ◽  
Mixing Performance ◽  
Chaotic Convection ◽  
The Deflection Angle ◽  
High Application

In this paper, we mainly study the mixing performance of the micromixer with quartic Koch curve fractal (MQKCF) by numerical simulation. Changing the structure of the microchannel based on the fractal principle can significantly improve the fluid flow state in the microchannel and improve the mixing efficiency of the micromixer. This paper discussed the effects of different fractal deflection angles, microchannel heights and different fractal times on the mixing efficiency under four different Reynolds numbers (Re). It is found that changing the deflection angle of the fractal can bring extremely high benefits, which makes the fluid deflect and fold in the microchannel, enhancing the chaotic convection in the microchannel, and improve the mixing efficiency of the fluid. Under the reasonable arrangement of the quartic Koch curve fractal principle, it can give the micro-mixture more than 99% mixing efficiency. Based on the excellent mixing performance of MQKCF, it also has extremely high application value in the biochemical neighborhood.

Analysis of a Novel Y-Y Micromixer for Mixing at a Wide Range of Reynolds Numbers

2016 ◽  
Vol 138 (9) ◽  
Author(s):  
Vladimir Viktorov ◽  
Carmen Visconte ◽  
Md Readul Mahmud
Keyword(s):  
Three Dimensional ◽  
Interfacial Area ◽  
Reynolds Numbers ◽  
Mixing Efficiency ◽  
Change Of Direction ◽  
Analysis Technique ◽  
Wide Range ◽  
Passive Micromixer ◽  
In Series ◽  
Flow Through

A novel passive micromixer, denoted as the Y-Y mixer, based on split-and-recombine (SAR) principle is proposed and studied both experimentally and numerically over Reynolds numbers ranging from 1 to 100. Two species are supplied to a prototype via a Y inlet, and flow through four identical elements repeated in series; the width of the mixing channel varies from 0.4 to 0.6 mm, while depth is 0.4 mm. An image analysis technique was used to evaluate mixture homogeneity at four target areas along the mixer. Numerical simulations were found to be a useful support for observing the complex three-dimensional flow inside the channels. Comparison with a known mixer, the tear-drop one, based on the same SAR principle, was also performed, to have a point of reference for evaluating performances. A good agreement was found between numerical and experimental results. Over the examined range of Reynolds numbers Re, the Y-Y micromixer showed at its exit an almost flat mixing characteristic, with a mixing efficiency higher than 0.9; conversely, the tear-drop mixer showed a relevant decrease of efficiency at the midrange. The good performance of the Y-Y micromixer is due to the three-dimensional 90 deg change of direction that occurs in its channel geometry, which causes a fluid swirling already at the midrange of Reynolds numbers. Consequently, the fluid path is lengthened and the interfacial area of species is increased, compensating for the residence time reduction.

Numerical simulation of three-dimensional passive micromixer based on the principle of Koch fractal

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Siyue Xiong ◽  
Xueye Chen
Keyword(s):  
Numerical Simulation ◽  
Fluid Flow ◽  
Cross Section ◽  
Three Dimensional ◽  
Mixing Efficiency ◽  
Mixing Performance ◽  
Chaotic Convection ◽  
Passive Micromixer ◽  
Koch Fractal ◽  
Koch Fractal Principle

Abstract In this paper, We arrange the obstacles based on the Koch fractal principle (OKF) in the micromixer. By changing the fluid flow and folding the fluid, a better mixing performance is achieved. We improve the mixing efficiency by placing OKF and changing the position of OKF, then we studied the influence of the number of OKF and the height of the micromixer on the mixing performance. The results show that when eight OKF are staggered in the microchannel and the height is 0.2 mm, the mixing efficiency of the OKF micromixer can reach 97.1%. Finally, we compared the velocity cross section and velocity streamline of the fluid, and analyzed the influence of OKF on the concentration trend. Through analysis, it is concluded that OKF can generate chaotic convection in the fluid, and enhance the mixing of fluids by generating vortices and folding the fluid. It can effectively improve the mixing efficiency of the micromixer.

Numerical Simulation of a Novel Passive Micromixer With Curved Channel and Slanted Grooves

2010 ◽  
Author(s):  
Yanfeng Fan ◽  
Ibrahim Hassan
Keyword(s):  
Numerical Simulation ◽  
Rotation Angle ◽  
Flow Characteristics ◽  
Reynolds Numbers ◽  
Mixing Efficiency ◽  
Curved Channel ◽  
Passive Micromixer ◽  
Present Design ◽  
High Reynolds ◽  
Rotation Strength

A novel passive micromixer with slanted grooves on the top and bottom of curved microchannel, denoted as CMG, is investigated numerically. The total mixing length is fixed at approximate 5.17 mm. The curved channel is applied to generate Dean vortices in the microchannel at high Reynolds numbers. The slanted grooves are used to assist to create the rotation of flow at low Reynolds numbers. The validation of present numerical simulation is done through the comparison with literatures. Three parameters, the slanted angle (θ), the grooves width angle (ω), and the height ratio of grooves (Hg/H), are selected to achieve the optimization. The tested Reynolds numbers range from 1 to 50. Compared with slanted grooved micromixer (SGM) and the curved microchannel (CM), the present micromixer has better mixing efficiency. In order to investigate the flow characteristics, a particle located at one inlet is selected and the trajectory is performed to observe the flow rotation. The rotation angle is defined to estimate the rotation strength. The results show that CMG has largest rotation angle than CM and SGM, which indicates a stronger rotation/helical motion generated in the curved channel. The mixing efficiency of present design has 60% at Re = 50 with a pressure drop of 1.8 kPa.

Thermal Transport in a Microchannel Exhibiting Ultrahydrophobic Microribs Maintained at Constant Temperature

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
D. Maynes ◽  
B. W. Webb ◽  
J. Davies
Keyword(s):  
Nusselt Number ◽  
Pressure Drop ◽  
Laminar Flow ◽  
Constant Temperature ◽  
Thermal Transport ◽  
Flow Direction ◽  
Relative Size ◽  
Reynolds Numbers ◽  
Frictional Pressure Drop ◽  
Smooth Channel

This paper presents numerical results exploring the periodically repeating laminar flow thermal transport in a parallel-plate microchannel with ultrahydrophobic walls maintained at constant temperature. The walls considered here exhibit alternating microribs and cavities positioned perpendicular to the flow direction. Results describing the thermally periodically repeating dynamics far from the inlet of the channel have been obtained over a range of laminar flow Reynolds numbers and relative microrib/cavity module lengths and depths in the laminar flow regime. Previously, it has been shown that significant reductions in the overall frictional pressure drop can be achieved relative to the classical smooth channel laminar flow. The present predictions reveal that the overall thermal transport is also reduced as the relative size of the cavity region is increased. The overall Nusselt number behavior is presented and discussed in conjunction with the frictional pressure drop behavior for the parameter range explored. The following conclusions can be made regarding thermal transport for a constant temperature channel exhibiting ultrahydrophobic surfaces: (1) Increases in the relative cavity length yield decreases in the Nusselt number, (2) increasing the relative rib/cavity module length yields a decrease in the Nusselt number, and (3) decreases in the Reynolds number result in smaller values of the Nusselt number.

Direct Numerical Simulation of the Pressure Drop through Structured Porous Media

2015 ◽  
Vol 364 ◽  
pp. 192-200 ◽  
Author(s):  
I. Malico ◽  
C. Ferrão ◽  
P.J.S.A. Ferreira de Sousa
Keyword(s):  
Porous Media ◽  
Pressure Drop ◽  
Flow Direction ◽  
Particle Diameter ◽  
Reynolds Numbers ◽  
Immersed Boundary ◽  
Square Cylinders ◽  
Compact Finite Differences ◽  
Flow Through ◽  
Semi Empirical

This paper presents direct numerical simulations for the flow through regular porous media composed of equal size staggered square cylinders obtained with a compact finite differences immersed boundary method. Different moderate Reynolds numbers are simulated in order to capture the dependence of the pressure drop with the Reynolds number in the Forchheimer regime. The pressure drop predictions agree well with the Hazen-Dupuit-Darcy model; however, when compared to a widely used semi-empirical correlation, the modified Ergun equation, the agreement is poor. A better agreement is found if the particle diameter is taken to be equal to the cylinder diameter. From the intrinsic-averaged pressure calculated along the flow direction, it can be seen that, for the porous media studied, the bulk pressure drop dominates and the entrance and exit effects are negligible.

Numerical Investigation and Geometric Parameterization of Lamination Inlet of Passive Micromixer

2010 ◽  
Author(s):  
Yanfeng Fan ◽  
Ibrahim Hassan
Keyword(s):  
Flow Characteristics ◽  
Reynolds Numbers ◽  
Mixing Efficiency ◽  
Mixing Length ◽  
Straight Channel ◽  
Interface Area ◽  
Mixing Performance ◽  
Passive Micromixer ◽  
Two Parameters ◽  
Parallel Type

A lamination inlet is proposed and optimized in this paper. The perpendicular incoming fluids are applied instead of parallel type. The total mixing length is fixed at 3.2 mm and the depth of channel is fixed at 0.1 mm. The tested Reynolds number is calculated at the entrance of downstream straight channel. The tested Reynolds numbers range from 5 to 200. The perpendicular incoming type enhances the mass-convection and enlarges the interface area. Two parameters, the radius of holes (R) and the distance between two holes (D1), are selected to achieve the optimization. Numerical simulation is used to estimate the mixing performance and flow characteristics. The results show that the vortices are generated in the microchannel. The interface becomes irregular. In order to evaluate the mixing improvement, the parallel lamination is also simulated. The comparison shows that the perpendicular inlet type has better mixing efficiency than the parallel lamination type. This inlet type could be connected with certain mixing element to achieve the applications in biochemistry.

Parametric Study of Obstacle Geometry Effect on Mixing Performance in a Convergent-Divergent Micromixer with Sinusoidal Walls

2017 ◽  
Vol 12 (1) ◽  
Author(s):  
Fazlollah Heshmatnezhad ◽  
Halimeh Aghaei ◽  
Ali Reza Solaimany Nazar
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Aspect Ratio ◽  
Molecular Diffusion ◽  
Reynolds Numbers ◽  
Secondary Flows ◽  
Mixing Efficiency ◽  
Main Concept ◽  
Mixing Index ◽  
Operational Parameter

Abstract This study presents a numerical simulation through computational fluid dynamics on mixing and flow structures in convergent-divergent micromixer with a triangular obstacle. The main concept in this design is to enhance the interfacial area between the two fluids by creating a transverse flow and split, and recombination of fluids flow due to the presence of obstacles. The effect of triangular obstacle size, the number of units, changing the position of an obstacle in the mixing channel and operational parameter like the Reynolds number on the mixing efficiency and pressure drop are assessed. The results indicate that at inlet Reynolds numbers below 5, the molecular diffusion is the most important mechanism of mixing, and the mixing index is almost the same for all cases. By increasing the inlet Reynolds number above 5, mixing index increases dramatically, due to the secondary flows. Based on the simulation results, due to increasing the effect of dean and separation vortices as well as more recirculation of flow in the side branches and behind the triangular obstacle, the highest mixing index is obtained at the aspect ratio of 2 for the triangular obstacle and its position at the front of the mixing unit. Also the highest value of mixing index is obtained by six unit of mixing chamber. The effect of changing the position of the obstacle in the channel and changing the aspect ratio of the obstacle is evident in high Reynolds numbers. An increase in the Reynolds number in both cases (changing the aspect ratio and position of the obstacle) leads to pressure drop increases.

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