On effects of shape, aspect ratio and position of obstacle on the mixing enhancement in micromixer with hexagonal-shaped chambers

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Ranjitsinha R. Gidde
Keyword(s):  
Pressure Drop ◽  
Aspect Ratio ◽  
Reynold Number ◽  
Transverse Flow ◽  
Performance Characteristics ◽  
Chaotic Advection ◽  
Mixing Enhancement ◽  
Mixing Index ◽  
Mixing Performance ◽  
Mixing Dynamics

AbstractThe micromixer geometry presented consists of T-type micromixer with premixing chamber, hexagonal shaped chambers and obstacles. In order to observe influences of obstacle shape, aspect ratio and position, simulations are carried out for two types of obstacle shapes viz. rectangular and triangular for the Reynold number in the range from 0.1 to 75. Flow and mixing dynamics are studied to investigate the effect of geometric modifications for identifying the mixing mechanisms. The effect of obstacle shape, aspect ratio and position is investigated using the performance characteristics viz. mixing index and pressure drop quantitatively. Both the micromixers demonstrate different mixing mechanisms, including transverse flow, vortices and chaotic advection due to split and recombination action. The mixing performance is diffusion dominated below Re < 5 and it is advection dominated beyond Re > 5. At Re ≥ 20, the mixing index observed is 0.80 in all the micromixer design configurations.

scholarly journals Numerical Analysis of Liquid Mixing in a T-Micromixer with Taylor Dispersion Obstructions

2019 ◽  
Vol 5 (1) ◽  
pp. 147-160
Author(s):  
T. Manoj Dundi ◽  
S. Chandrasekhar ◽  
Shasidar Rampalli ◽  
V. R. K. Raju ◽  
V. P. Chandramohan
Keyword(s):  
Biomedical Engineering ◽  
Flow Direction ◽  
Taylor Dispersion ◽  
Chaotic Advection ◽  
Mixing Enhancement ◽  
Chemical Processing ◽  
Inertial Effects ◽  
Mixing Performance ◽  
Velocity Gradients

Passive micromixers are of great importance in biomedical engineering (lab-on-chips) and chemical processing (microreactors) fields. Various hydrodynamic principles such as lamination, flow separation, and chaotic advection were employed previously to improve mixing in passive mixers. However, mixing enhancement due to velocity gradients in the flow, which is known as the Taylor dispersion effect, has been seldom studied. In the present study, thin rectangular slabs oriented in the flow direction are placed in the mixing channel of a T-micromixer. The thin rectangular slabs are referred to as Taylor Dispersion Obstructions (TDOs) as they are designed to create velocity gradients in the flow. The mixing performance of T-micromixer with and without TDOs is estimated in the Re range of 0 to 350. It is observed that there is no effect on mixing in the presence of TDOs in the low Re (0 < Re < 100), as the velocity gradients created in the flow are considerably small. The vortex formed in the flow for Re of 100 to 220 damped the gradients of velocity created in the flow (due to the presence of TDOs) which resulted in negligible improvement in the quality of mixing. However, considerable enhancement in mixing performance is obtained at high Re (250 to 350) with the presence of TDOs in the mixer. The increase in inertial effects at higher Recreated larger gradients of velocity near the walls of TDOs and mixing channel walls and thereby a significant enhancement in mixing performance is obtained due to Taylor dispersion.

Flow Feature Analysis of T-Junction Wavy Micromixer for Mixing Application

2019 ◽  
Vol 17 (9) ◽  
Author(s):  
Ranjitsinha R. Gidde ◽  
Prashant M. Pawar
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Performance Index ◽  
Feature Analysis ◽  
Pumping Power ◽  
Mixing Index ◽  
Wavy Channel ◽  
Mixing Performance ◽  
Flow Feature ◽  
Side Walls

Abstract The mixing of fluids in wavy micromixer and wavy micromixer with obstacles on its side walls has been numerically investigated. The effect of frequency of wavy channel on mixing performance is studied over a range of Reynolds number from 0.1 to 45. Various performance characteristics viz. the mixing index, pressure drop, performance index, and pumping power are used to analyze the overall mixing performance. The results show that the wavy micromixer with obstacles produces better mixing performance than the wavy micromixer. Also, the mixing index is sensitive to the wavy frequency of the channel. The wavy micromixer exhibits the smallest pressure drop as compared to micromixer with obstacles in all cases.

scholarly journals Numerical study of mixing index in offset inlets 3-D T mixer with bend shape mixing channel

2021 ◽  
Author(s):  
Ranjan Prakash ◽  
◽  
Mohammad Zunaid ◽  
Samsher Samsher ◽  
◽  
...  
Keyword(s):  
Aspect Ratio ◽  
Cfd Simulation ◽  
Numerical Study ◽  
Momentum Equation ◽  
Chaotic Advection ◽  
Width Ratio ◽  
Mixing Index ◽  
Conservation Of Energy ◽  
Conservation Of Momentum ◽  
Bend Shape

The objective of this paper is the computational analysis on the mixing index of simple T shape mixer, offset inlets T shape mixer, and offset inlets T mixer with bend shape mixing channel by CFD simulation. Computational fluid dynamics software package solves conservation of mass equation, conservation of momentum equation, and conservation of energy equation. In the case of offset inlets T shape mixer, as the aspect ratio (height to width ratio) of mixing channel increased so mixing quality also increased and offset inlets T mixer with bend shape is a combination of increased aspect ratio as well as chaotic advection mechanisms, so it provides advanced mixing index than offset inlets T shape mixer and simple T shape mixer. Pressure fall in offset inlets T shape mixer is excess than simple T shape mixer but narrowly degraded than offset inlets T mixer with bend shape. Chaotic advection rooted microchannel generates secondary flow because of which motives a high-pressure drop in the microchannel.

Analysis of mixing performances in microchannel with obstacles of different aspect ratios

2019 ◽  
Vol 233 (5) ◽  
pp. 1045-1051 ◽  
Author(s):  
Bappa Mondal ◽  
Sukumar Pati ◽  
PK Patowari
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Aspect Ratio ◽  
Flow Condition ◽  
Schmidt Number ◽  
Mixing Efficiency ◽  
Rectangular Microchannel ◽  
Mixing Performance ◽  
Aspect Ratios ◽  
Flow Through

In this study, the mixing performance and pressure drop characteristics have been numerically analyzed for flow through rectangular microchannel with obstacles in the walls arranged in a staggered manner. Three different aspect ratios (AR) of the obstacles are considered, namely 4:1, 1:1, and 1:4. The effects of aspect ratio of the obstacles on the mixing efficiency and the pressure drop are analyzed and compared with that of the channel without obstacle. The results are presented in terms of Reynolds number (Re) and Schmidt number (Sc) in the following range: 0.2 ≤ Re ≤ 1 and 500 ≤ Sc ≤ 1500. Enhanced mixing efficiency is achieved for the case of microchannel with obstacles and the corresponding pressure drop is also found to be higher. The mixing efficiency as well as the pressure drop is maximum for AR = 1:4 among all the geometries considered in the analysis in same flow condition. Furthermore, for a given configuration of the microchannel the mixing efficiency is governed by the mass Peclet number and, accordingly, the mixing efficiency increases with the decrease in Schmidt number for a given Reynolds number.

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.

Effects of Obstacles on the Mixing Performance in Microchannels

2007 ◽  
Author(s):  
Tae-An Kim ◽  
Youn-Jea Kim
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Aspect Ratio ◽  
Lower Layer ◽  
Flow Direction ◽  
Diffusion Path ◽  
Mixing Efficiency ◽  
Convection Flow ◽  
Rectangular Microchannel ◽  
Mixing Performance

The mixing of two or more fluid streams in microchannels needs quite long channel lengths. Therefore, in order to improve the mixing performance, obstacles have been placed in the channel to disrupt flow and to reduce the diffusion path. The disruption to flow velocity field alters the flow direction from one fluid to another. Properly designed geometric parameters, such as layout, angle with main flow direction and aspect ratio of obstacles, will be resulted in improving the mixing performance with only little increase of the pressure drop. In this study, T-type rectangular microchannel is used, which has two inlets with W×H×L = 100×100×100 μm3 and one outlet with W×H×L = 200×100×6950 μm3. Furthermore, the mixing channel has obstacles which are placed with an angle of inclination and with dimensions W×H×L = 10×100×h μm3 on the lower layer. In order to estimate the performance of the mixing, numerical analyses are carried out with water and ethanol. Especially, the diffusion coefficient, D, is set to 10−10 m2/s for simulating two-fluid diffusion-convection flow, the mixing efficiency and the pressure drop of microchannel are investigated with various values of the angle of inclination, aspect ratio (h = αH) of obstacle and Reynolds number. When the flow passes through on the obstacles, rotation flow is observed. This flow pattern is repeated at each cycle. Besides, in each case that obstacles are turned to the center of channel and to the side walls, rotational direction is changed reversely. In case of pressure drop, as the Reynolds number, the angle of obstacle (θ) and the aspect ratio (α) are increased, the pressure drop is also increased. Results show that the ratio between the maximum and minimum of pressure drop is the order-of-magnitude of 1 at Re = 1.667. Results also show that the angle of inclination of obstacles has more influence on the mixing performance than the height of obstacles and Reynolds number.

scholarly journals Clogging sensitivity of flow distributors designed for radially elongated hexagonal pillar array columns: a computational modelling

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Farideh Haghighi ◽  
Zahra Talebpour ◽  
Amir Sanati-Nezhad
Keyword(s):  
Pressure Drop ◽  
Aspect Ratio ◽  
Contact Zone ◽  
Separation Efficiency ◽  
Fluid Dynamic ◽  
Computational Modelling ◽  
Channel Width ◽  
Fluid Distribution ◽  
Design Parameters ◽  
Pillar Array

AbstractFlow distributor located at the beginning of the micromachined pillar array column (PAC) has significant roles in uniform distribution of flow through separation channels and thus separation efficiency. Chip manufacturing artifacts, contaminated solvents, and complex matrix of samples may contribute to clogging of the microfabricated channels, affect the distribution of the sample, and alter the performance of both natural and engineered systems. An even fluid distribution must be achieved cross-sectionally through careful design of flow distributors and minimizing the sensitivity to clogging in order to reach satisfactory separation efficiency. Given the difficulty to investigate experimentally a high number of clogging conditions and geometries, this work exploits a computational fluid dynamic model to investigate the effect of various design parameters on the performance of flow distributors in equally spreading the flow along the separation channels in the presence of different degrees of clogging. An array of radially elongated hexagonal pillars was selected for the separation channel (column). The design parameters include channel width, distributor width, aspect ratio of the pillars, and number of contact zone rows. The performance of known flow distributors, including bifurcating (BF), radially interconnected (RI), and recently introduced mixed-mode (MMI) in addition to two new distributors designed in this work (MMII and MMIII) were investigated in terms of mean elution time, volumetric variance, asymmetry factors, and pressure drop between the inlet and the monitor line for each design. The results show that except for pressure drop, the channel width and aspect ratio of the pillars has no significant influence on flow distribution pattern in non-clogged distributors. However, the behavior of flow distributors in response to clogging was found to be dependent on width of the channels. Also increasing the distributor width and number of contact zone rows after the first splitting stage showed no improvement in the ability to alleviate the clogging. MMI distributor with the channel width of 3 µm, aspect ratio of the pillars equal to 20, number of exits of 8, and number of contact zones of 3 exhibited the highest stability and minimum sensitivity to different degrees of clogging.

scholarly journals Effect of Aspect Ratio on the Mixing Performance in the Kenics Static Mixer

Processes ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 464
Author(s):  
Xingren Jiang ◽  
Ning Yang ◽  
Rijie Wang
Keyword(s):  
Pharmaceutical Industry ◽  
Aspect Ratio ◽  
Flow Reactor ◽  
Mixing Time ◽  
Continuous Process ◽  
Scale Up ◽  
Influence Factors ◽  
Continuous Manufacturing ◽  
Static Mixer ◽  
Mixing Performance

Continuous manufacturing has received increasing interest because of the advantages of intrinsic safety and enhanced mass transfer in the pharmaceutical industry. However, the difficulty for scale-up has limited the application of continuous manufacturing for a long time. Recently, the tubular flow reactor equipped with the Kenics static mixer appears to be a solution for the continuous process scale-up. Although many influence factors on the mixing performance in the Kenics static mixer have been investigated, little research has been carried out on the aspect ratio. In this study, we used the coefficient of variation as the mixing evaluation index to investigate the effect of the aspect ratio (0.2–2) on the Kenics static mixer’s mixing performance. The results indicate that a low aspect ratio helps obtain a shorter mixing time and mixer length. This study suggests that adjusting the aspect ratio of the Kenics static mixer can be a new strategy for the scale-up of a continuous process in the pharmaceutical industry.

Numerical analysis of non-aligned inputs M-type micromixers with different shaped obstacles for biomedical applications

2021 ◽  
pp. 095440892110516
Author(s):  
Muhammad Irfan ◽  
Imran Shah ◽  
Usama M Niazi ◽  
Muhsin Ali ◽  
Sadaqat Ali ◽  
...  
Keyword(s):  
Structural Design ◽  
Biomedical Applications ◽  
Structural Changes ◽  
Nanoparticle Synthesis ◽  
Fluid Mixing ◽  
The Novel ◽  
Flow Conditions ◽  
Mixing Index ◽  
Mixing Performance ◽  
Passive Micromixer

Fluid mixing in lab-on-a-chip devices at laminar flow conditions result in a low mixing index. The reason is dominant diffusion over the convection process. The mixing index can be improved by certain changes in the micromixer structural design like introducing obstacles in the path of fluid flow. These obstacles will make dominant the advection process over the diffusion process. The main contribution of this work is based on proposing the novel hybrid type micromixer design for enhancing the mixing quality. Three non-aligned M-type and non-aligned M-type with obstacles passive type micromixers are analyzed by COMSOL5.5. These designs are hybrid types because different structural changes are combined in a single design for mixing improvement. First of all the straight non-aligned inlets, M-type passive micromixer (SMTM) is analyzed. It is observed that mixing performance is improved because of M-shaped mixing units and non-aligned inlets. This improvement is deemed to be not enough so different shaped obstacles are introduced in the micromixer design. These designs based on obstacles are named horizontal rectangular M-type micromixer, square M-type micromixer, and vertical rectangular M-type micromixer. The mixing index for SMTM, square M-type micromixer, horizontal rectangular M-type micromixer, and vertical rectangular M-type micromixer at Reynolds number Re = 60 is respectively given by 71.1%, 83.21%, 84.45%, and 89.99%. The mixing index of vertical rectangular M-type micromixer was 59.34% − 87.65% for Re = 0.5–100. Vertical rectangular M-type micromixer is concluded with the better-mixing capability design among the proposed ones. Based on these simulation results, the vertical rectangular M-type micromixer design can be utilized for mixing purposes in biomedical applications like nanoparticle synthesis and biomedical sample preparation for drug delivery.

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