scholarly journals Enhancement of Fluid Mixing with U-Shaped Channels on a Rotating Disc

Micromachines ◽  
2020 ◽  
Vol 11 (12) ◽  
pp. 1110
Author(s):  
Chi-Wei Hsu ◽  
Po-Tin Shih ◽  
Jerry M. Chen
Keyword(s):  
Secondary Flow ◽  
Rotational Speed ◽  
Fluid Mixing ◽  
Maximum Efficiency ◽  
Mixing Efficiency ◽  
Rotating Disc ◽  
Mixing Performance ◽  
Simple Geometry ◽  
Visualization Experiments ◽  
Good Agreement

In this study, centrifugal microfluidics with a simple geometry of U-shaped structure was designed, fabricated and analyzed to attain rapid and efficient fluid mixing. Visualization experiments together with numerical simulations were carried out to investigate the mixing behavior for the microfluidics with single, double and triple U-shaped structures, where each of the U-structures consisted of four consecutive 90° bends. It is found that the U-shaped structure markedly enhances mixing by transverse secondary flow that is originated from the Coriolis-induced vortices and further intensified by the Dean force generated as the stream turns along the 90° bends. The secondary flow becomes stronger with increasing rotational speed and with more U-shaped structures, hence higher mixing performance. The mixing efficiency measured for the three types of mixers shows a sharp increase with increasing rotational speed in the lower range. As the rotational speed further increases, nearly complete mixing can be achieved at 600 rpm for the triple-U mixer and at 720 rpm for the double-U mixer, while a maximum efficiency level of 83–86% is reached for the single-U mixer. The simulation results that reveal detailed characteristics of the flow and concentration fields are in good agreement with the experiments.

Evaluation of the Mixing Performance of the Micromixers With Grooved or Obstructed Channels

2008 ◽  
Vol 130 (7) ◽  
Author(s):  
Yeng-Yung Tsui ◽  
Ching-Shiang Yang ◽  
Chung-Ming Hsieh
Keyword(s):  
Vertical Plane ◽  
Pressure Head ◽  
Fluid Mixing ◽  
Mixing Performance ◽  
Large Pressure ◽  
Fluid Concentration ◽  
Speed Up ◽  
Periodic Configuration ◽  
The Cost ◽  
Good Agreement

The mixing flows in microchannels were examined using numerical methods. To speed up fluid mixing, it is essential to generate lateral transport of mass. In this study, the mixing flow is disrupted by either placing grooves or block obstacles on the walls of the channels. Since the grooves or the blocks appear in a periodic configuration, the velocity is solved only in a section of the channel. With the repeating cycle of flow velocity field, the fluid concentration can be calculated throughout the entire length of the channel. Good agreement with experiments in the mixing performance justifies the present methodology. Two different channel configurations are under consideration: grooved channels and obstructed channels. The results reveal that with straight grooves, a well organized vortex flow is formed in the vertical plane along the groove, which leads to a helical flow in the channel. The mixing performance can be enhanced by having grooves on both the top and the bottom walls arranged in a staggered manner, by which the transversal velocity is largely increased. It is seen that the strength of the secondary flow and, thus, the mixing can be improved by suitably choosing geometric parameters of the groove, such as the depth, the width, and the oblique angle. It is also shown that the efficient mixing for the staggered herringbone type groove is due to the fluid stratification caused by the exchange of position of the resulted counter-rotating vortices. As for the obstructed channels, the flows are in essence two dimensional. Very strong transversal velocity can be produced by narrowing down the flow passage in the channel. However, the efficient mixing is obtained at the cost of large pressure head loss.

Numerical Study of Fluid Mixing in a Microchannel with a Circular Chamber on a Rotating Disk

2012 ◽  
Vol 542-543 ◽  
pp. 1113-1119 ◽  
Author(s):  
Huan Chao Chiu ◽  
Jerry M Chen
Keyword(s):  
Rotational Speed ◽  
Numerical Study ◽  
Rotating Disk ◽  
Transverse Flow ◽  
Fluid Mixing ◽  
Mixing Efficiency ◽  
Straight Channel ◽  
Lower Range ◽  
Speed Range ◽  
Flat Distribution

This paper reports numerical simulations of fluid mixing in a rotating microchannel with a microchamber fabricated on a CD-like substrate. The sample fluids are driven by the centrifugal force and brought in contact at a Y-shaped junction, and then the mixing flow moves through a straight channel with a circular chamber where the main course of mixing takes place. The CD-like micromixer is rotated clockwise at speeds ranging from 300 to1200 rpm. With increasing rotational speed, the mixing efficiency is found dropping in the lower range (≤ 540 rpm), where the diffusion still dominates the mixing, and then grows progressively to reach as much as 90%. The progressively growth in the higher speed range significantly improves the slightly descending and flat distribution for a straight mixing channel without a circular chamber. This significant enhancement of mixing is due mainly to the vortices generated in the circular chamber and the strong transverse flow induced by the Coriolis force.

Experimental and Numerical Investigation into Mixing Efficiency of Micromixers with Different Geometric Barriers

2006 ◽  
Vol 505-507 ◽  
pp. 391-396 ◽  
Author(s):  
Chia Yen Lee ◽  
Chiufeng Lin ◽  
M.F. Hung ◽  
R.H. Ma ◽  
Chien Hsiung Tsai ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Numerical Investigation ◽  
Low Cost ◽  
Experimental Results ◽  
Mixing Efficiency ◽  
Mixing Performance ◽  
Side Channels ◽  
Liquid Samples ◽  
Glass Slides ◽  
Good Agreement

This paper proposes a numerical and experimental investigation of mixing behaviors of two liquid samples in microchannels that are shaped into different geometric barriers. The micro-mixers utilized in this study are fabricated on low-cost glass slides using a simple and reliable fabrication process. Samples are driven by a hydrodynamic pump to lead them into the mixing section of the microchannels. The effects of mixing performance of various kinds of barrier shape are discussed in this study. The numerical and experimental results show that a better mixing efficiency can be obtained in the microchannels while using the elliptic-shape barriers in compare with the leaking side-channels. In this study, the simulated and experimental results are in good agreement. The investigation of mixing efficiency in microchannels with different geometric barriers could be crucial for microfluidic systems.

scholarly journals Effect of Thermal Energy and Ultrasonication on Mixing Efficiency in Passive Micromixers

Processes ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 891
Author(s):  
Fahizan Mahmud ◽  
Khairul Fikri Tamrin ◽  
Shahrol Mohamaddan ◽  
Nobuo Watanabe
Keyword(s):  
Thermal Energy ◽  
Reynolds Numbers ◽  
Fluid Mixing ◽  
Structural Deformation ◽  
Energy Sources ◽  
Mixing Efficiency ◽  
Mixing Index ◽  
Mixing Performance ◽  
Lower Reynolds Number ◽  
Better Than

Micromixing is a key process in microfluidics technology. However, rapid and efficient fluid mixing is difficult to achieve inside the microchannels due to unfavourable laminar flow. Active micromixers employing ultrasound and thermal energy are effective in enhancing the micromixing process; however, integration of these energy sources within the devices is a non-trivial task. In this study, ultrasound and thermal energy have been extraneously applied at the upstream of the micromixer to significantly reduce fabrication complexity. A novel Dean micromixer was laser-fabricated to passively increase mixing performance and compared with T- and Y-micromixers at Reynolds numbers between 5 to 100. The micromixers had a relatively higher mixing index at lower Reynolds number, attributed to higher residence time. Dean micromixer exhibits higher mixing performance (about 27% better) than T- and Y-micromixers for 40 ≤ Re ≤ 100. Influence of ultrasound and heat on mixing is more significant at 5 ≤ Re ≤ 20 due to the prolonged mechanical effects. It can be observed that mixing index increases by about 6% to 10% once the temperature of the sonicated fluids increases from 30 °C to 60 °C. The proposed method is potentially useful as direct contact of the inductive energy sources may cause unwanted substrate damage and structural deformation especially for applications in biological analysis and chemical synthesis.

Visualization of Fluid Mixing in a Microchamber on a Rotating Disk

2008 ◽  
Author(s):  
H.-C. Chiu ◽  
J.-Y. Chen ◽  
Jerry M. Chen
Keyword(s):  
Rotational Speed ◽  
High Speed ◽  
Rotating Disk ◽  
Fluid Mixing ◽  
Mixing Efficiency ◽  
Channel Depth ◽  
Clockwise Rotation ◽  
Two Fluids ◽  
Speed Range ◽  
Lower Speed Range

This paper reports flow visualization experiments of fluid mixing in a microchamber on a rotating disk. The two centrifuge-driven sample fluids were brought in contact at the Y-junction microchannel and then flowed to a circular mixing chamber where the main course of mixing took place. The flow images were acquired using a micro-image-capturing unit in synchronization with the rotational motion to allow only one shot of the targeted object on the rotating disk per revolution. Both the visualization and quantification of flow images show that the mixing efficiency of the two fluids depends not only on the rotational speed but also on the depth of the channels. It is found that the mixing efficiency generally decrease with increasing rotational speed in the lower speed range (≤ 420 rpm). Beyond this lower speed range, the mixer with a larger channel depth h = 300 μm shows an increase of mixing efficiency with increasing rotational speed to reach as much as 83% at 1200 rpm. For the mixer with a smaller channel depth h = 200 μm, however, the mixing efficiency continues deceasing or becomes flat with increasing rotational speed. It is also found that the counter-clockwise rotation produces a better mixing efficiency than the clockwise rotation in the high speed range.

Measurement of growth rates for single crystals and pressed tablets of CuSO4.5 H2O on a rotating disc

1989 ◽  
Vol 54 (11) ◽  
pp. 2951-2961 ◽  
Author(s):  
Miloslav Karel ◽  
Jaroslav Nývlt
Keyword(s):  
Growth Rate ◽  
Single Crystal ◽  
Single Crystals ◽  
Growth Rates ◽  
Diffusion Coefficients ◽  
Preferred Orientation ◽  
Rotating Disc ◽  
Dissolution Rates ◽  
Rates Of Growth ◽  
Good Agreement

Measured growth and dissolution rates of single crystals and tablets were used to calculate the overall linear rates of growth and dissolution of CuSO4.5 H2O crystals. The growth rate for the tablet is by 20% higher than that calculated for the single crystal. It has been concluded that this difference is due to a preferred orientation of crystal faces on the tablet surface. Calculated diffusion coefficients and thicknesses of the diffusion and hydrodynamic layers in the vicinity of the growing or dissolving crystal are in good agreement with published values.

A low-profile FSS-based high capacity chipless RFID tag for sensing and encoding applications

2021 ◽  
pp. 1-9
Author(s):  
Shahid Habib ◽  
Amjad Ali ◽  
Ghaffer Iqbal Kiani ◽  
Wagma Ayub ◽  
Syed Muzahir Abbas ◽  
...  
Keyword(s):  
Radio Frequency Identification ◽  
High Capacity ◽  
Frequency Selective Surface ◽  
Rfid Tag ◽  
Sensing Applications ◽  
Low Profile ◽  
Simple Geometry ◽  
Chipless Rfid ◽  
Frequency Identification ◽  
Good Agreement

Abstract This paper presents a polarization-independent 11-bit chipless RFID tag based on frequency-selective surface which has been designed for encoding and relative humidity (RH) sensing applications. The 10 exterior U-shaped resonators are used for item encoding whereas Kapton has been incorporated with the interior resonator for RH sensing. This radio-frequency identification (RFID) tag operates in S- and C-frequency bands. The proposed design offers enhanced fractional bandwidth up to 88% with the density of 4.46 bits/cm2. Both single- and dual-layer tags have been investigated. The simulated results are in good agreement with measured results and a comparison with existing literature is presented to show the performance. Simple geometry, high code density, large frequency signature bandwidth, high magnitude bit, high radar cross-section, and angular stability for more than 75° are the unique outcomes of the proposed design. In addition, RH sensing has been achieved by integrating the Kapton on the same RFID tag.

Analysis of the First Order and Slowly Varying Motions of an Axisymmetric Floating Body in Bichromatic Waves

2013 ◽  
Vol 135 (1) ◽  
Author(s):  
João Pessoa ◽  
Nuno Fonseca ◽  
C. Guedes Soares
Keyword(s):  
Vertical Cylinder ◽  
Vertical Axis ◽  
Second Order ◽  
The Body ◽  
Floating Body ◽  
Drift Motion ◽  
First Order ◽  
Motion Responses ◽  
Simple Geometry ◽  
Good Agreement

The paper presents an experimental and numerical investigation on the motions of a floating body of simple geometry subjected to harmonic and biharmonic waves. The experiments were carried out in three different water depths representing shallow and deep water. The body is axisymmetric about the vertical axis, like a vertical cylinder with a rounded bottom, and it is kept in place with a soft mooring system. The experimental results include the first order motion responses, the steady drift motion offset in regular waves and the slowly varying motions due to second order interaction in biharmonic waves. The hydrodynamic problem is solved numerically with a second order boundary element method. The results show a good agreement of the numerical calculations with the experiments.

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.

Aerodynamic Similarity Principles and Scaling Laws for Windmilling Fans

2018 ◽  
Author(s):  
Dilip Prasad
Keyword(s):  
Rotational Speed ◽  
Pressure Loss ◽  
Scaling Laws ◽  
Dynamic Pressure ◽  
Stagnation Pressure ◽  
Design Parameters ◽  
Similarity Parameter ◽  
Wide Range ◽  
Simulation Results ◽  
Good Agreement

Windmilling requirements for aircraft engines often define propulsion and airframe design parameters. The present study is focused is on two key quantities of interest during windmill operation: fan rotational speed and stage losses. A model for the rotor exit flow is developed, that serves to bring out a similarity parameter for the fan rotational speed. Furthermore, the model shows that the spanwise flow profiles are independent of the throughflow, being determined solely by the configuration geometry. Interrogation of previous numerical simulations verifies the self-similar nature of the flow. The analysis also demonstrates that the vane inlet dynamic pressure is the appropriate scale for the stagnation pressure loss across the rotor and splitter. Examination of the simulation results for the stator reveals that the flow blockage resulting from the severely negative incidence that occurs at windmill remains constant across a wide range of mass flow rates. For a given throughflow rate, the velocity scale is then shown to be that associated with the unblocked vane exit area, leading naturally to the definition of a dynamic pressure scale for the stator stagnation pressure loss. The proposed scaling procedures for the component losses are applied to the flow configuration of Prasad and Lord (2010). Comparison of simulation results for the rotor-splitter and stator losses determined using these procedures indicates very good agreement. Analogous to the loss scaling, a procedure based on the fan speed similarity parameter is developed to determine the windmill rotational speed and is also found to be in good agreement with engine data. Thus, despite their simplicity, the methods developed here possess sufficient fidelity to be employed in design prediction models for aircraft propulsion systems.

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