NUMERICAL STUDY ON KOCH FRACTAL BAFFLE MICROMIXER

Fractals ◽  
2019 ◽  
Vol 27 (03) ◽  
pp. 1950026 ◽  
Author(s):  
SHUAI ZHANG ◽  
XUEYE CHEN ◽  
ZHONGLI WU ◽  
YUE ZHENG
Keyword(s):  
Numerical Study ◽  
Mixing Efficiency ◽  
Chaotic Convection ◽  
Koch Fractal ◽  
Better Than

This paper is mainly to study the application of Koch fractal baffle to passive micromixers. It can be determined that the mixing efficiency of secondary Koch fractal baffle (SKFB) micromixer is better than that of primary Koch fractal baffle (PKFB). We compare and analyze the mixing efficiency when the angle between the baffle and the microchannel is [Formula: see text], [Formula: see text] and [Formula: see text] with the height 100[Formula: see text][Formula: see text]m. With the changing of the angle, it contributes to enhance the chaotic convection of the micromixer. Especially at the angle of [Formula: see text], the vortex caused by the Koch fractal baffle structure is more obvious, the mixing efficiency of micromixer is more than 95% at Re [Formula: see text] 0.05 and 100. When the height of Koch fractal baffle is 50, 75 and [Formula: see text]m, the mixing efficiency of the micromixer gradually increases. The whirling and spiral phenomenon of the streamlines increases the chaotic convection and promotes the improvement of the mixing efficiency. In the direction of microchannel, nine sections which have a significant effect on the mixing efficiency are investigated. The encircling and split phenomenon affected by the chaotic convection is shown in nine sections at Re [Formula: see text] 0.05, 10 and 100.

Numerical study on micromixers with smart-rhombic structure

2018 ◽  
Vol 32 (27) ◽  
pp. 1850301 ◽  
Author(s):  
Jiajia Xu ◽  
Xueye Chen ◽  
Yanlin Liu ◽  
Zhen Yao
Keyword(s):  
Numerical Simulation ◽  
High Throughput ◽  
Numerical Study ◽  
Considerable Effect ◽  
Geometric Parameters ◽  
Channel Width ◽  
Variable Method ◽  
Mixing Efficiency ◽  
Width Ratio ◽  
Chaotic Convection

In this paper, we have designed a rhombic microchannel plane micromixer (RMPM). The RMPM uses the principle of converging and diverging to improve the mixing efficiency. We improved the mixing efficiency by changing the rhombic angles and the rhombic channel width ratios. The influence of geometric parameters on mixing efficiency is analyzed by control of the variable method. Through the analysis of the numerical simulation, the RMPM can help increase the chaotic convection between different concentrations of fluids. The results of the study show that the rhombic angle and the width ratio of a microchannel can have a considerable effect on the mixing efficiency. The micromixer can be potentially useful in the future applications of rapid and high throughput mixing.

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.

scholarly journals A Numerical Study of Sub-Millisecond Integrated Mix-and-Inject Microfluidic Devices for Sample Delivery at Synchrotron and XFELs

2021 ◽  
Vol 11 (8) ◽  
pp. 3404
Author(s):  
Majid Hejazian ◽  
Eugeniu Balaur ◽  
Brian Abbey
Keyword(s):  
Molecular Dynamics ◽  
Flow Rate ◽  
Numerical Study ◽  
Three Dimensional ◽  
Microfluidic Devices ◽  
Liquid Jets ◽  
Mixing Efficiency ◽  
X Ray Diffraction ◽  
Cross Sectional ◽  
Time Required

Microfluidic devices which integrate both rapid mixing and liquid jetting for sample delivery are an emerging solution for studying molecular dynamics via X-ray diffraction. Here we use finite element modelling to investigate the efficiency and time-resolution achievable using microfluidic mixers within the parameter range required for producing stable liquid jets. Three-dimensional simulations, validated by experimental data, are used to determine the velocity and concentration distribution within these devices. The results show that by adopting a serpentine geometry, it is possible to induce chaotic mixing, which effectively reduces the time required to achieve a homogeneous mixture for sample delivery. Further, we investigate the effect of flow rate and the mixer microchannel size on the mixing efficiency and minimum time required for complete mixing of the two solutions whilst maintaining a stable jet. In general, we find that the smaller the cross-sectional area of the mixer microchannel, the shorter the time needed to achieve homogeneous mixing for a given flow rate. The results of these simulations will form the basis for optimised designs enabling the study of molecular dynamics occurring on millisecond timescales using integrated mix-and-inject microfluidic devices.

scholarly journals On the optimal control force applied to tuned mass dampers for multi-degree-of-freedom systems

2004 ◽  
Vol 26 (1) ◽  
pp. 1-10
Author(s):  
Nguyen Dong Anh ◽  
Nguyen Chi Sang
Keyword(s):  
Optimal Control ◽  
Numerical Study ◽  
Degree Of Freedom ◽  
Control Force ◽  
Linear Quadratic ◽  
Tuned Mass Dampers ◽  
Coloured Noise ◽  
Optimal Theory ◽  
The One ◽  
Better Than

The design of active TMD for multi-degree-of-freedom systems subjected to second order coloured noise excitation is considered using the linear quadratic optimal theory. A detailed numerical study is carried out for a 2-DOF system. It is shown that the effectiveness of active TMD is better than the one of passive TMD.

scholarly journals A numerical study for convection in a cylindrical model with continuously varying viscosity

1996 ◽  
Vol 39 (3) ◽  
Author(s):  
F. Fanucci ◽  
A. Megna ◽  
S. Santini ◽  
F. Vetrano
Keyword(s):  
Viscosity Solutions ◽  
Numerical Study ◽  
Viscosity Coefficient ◽  
Cylindrical Symmetry ◽  
The Earth ◽  
Realistic Representation ◽  
Convective Motions ◽  
Constant Viscosity ◽  
Varying Viscosity ◽  
Better Than

In the framework of a cylindrical symmetry model for convective motions in the asthenosphere, a new profile for the viscosity coefficient depending on depth is suggested here. The numerical elaboration of the above mentioned model leads to interesting results which fit well with experimental observations. In particular these continuously varying viscosity solutions probably describe the convective motions within the Earth better than simple constant viscosity solutions. Consequently the temperature values seem to be a realistic representation of the possible thermal behaviour in the upper mantle.

Simulation of Two Designs of Micro-Mixers With Enhanced Advection Mechanisms

2011 ◽  
Author(s):  
S. A. Kazemi ◽  
M. Passandideh-Fard ◽  
J. Esmaeelpanah
Keyword(s):  
Numerical Study ◽  
Control Volume ◽  
Numerical Technique ◽  
Chaotic Advection ◽  
Mixing Efficiency ◽  
Mixing Length ◽  
Surface Development ◽  
Mixer Design ◽  
Gas Liquid Flow ◽  
Micro Mixer

In this paper, a numerical study of two new designs of passive micro-mixers based on chaotic advection is presented. The advection phenomenon in a T-shaped micro-mixer is enhanced using a segmented gas-liquid flow; and a peripheral/axial mixing mechanism. The simulations are performed for two non-reactive miscible gases: oxygen and methanol. The numerical model employed for this study is based on the solution of the physical governing equations namely the continuity, momentum, species transport and an equation to track the free surface development. The equations are discretized using a control volume numerical technique. The distribution of the species concentration within the domain is calculated based on which a mixing intensity factor is introduced. This factor is then used as a criterion for the mixing length. In the first micro-mixer design with a drop injection mechanism for a typical condition, the mixing length is reduced by nearly 15%. Compared to that of a simple T-shaped micro-mixer with the same flow rates, the two gases interface area is increased in axisymmetric micro-mixer leading to an increase of the mixing efficiency and a reduction of the mixing length. Also, the effects of the baffles height and span on the mixing efficiency and length in axisymmetric micro-mixer are studied. Having baffles in the channel can substantially decrease the mixing length.

scholarly journals Parabolic Pulse Generation Using Tapered Microstructured Optical Fibres

2008 ◽  
Vol 2008 ◽  
pp. 1-10 ◽  
Author(s):  
Natasha Vukovic ◽  
Neil G. R. Broderick ◽  
Francesco Poletti
Keyword(s):  
Pulse Shape ◽  
Pulse Shaping ◽  
Numerical Study ◽  
Pulse Generation ◽  
Optical Fibres ◽  
Step Index ◽  
Index Fibre ◽  
Microstructured Optical Fibres ◽  
Misfit Parameter ◽  
Better Than

This paper presents a numerical study of parabolic pulse generation in tapered microstructured optical fibres (MOFs). Based on our results and the algorithms presented, one can determine the linear taper profile (starting and finishing pitch values and taper length) needed to achieve parabolic pulse shaping of an initial Gaussian pulse shape with different widths and powers. We quantify the evolution of the parabolic pulse using the misfit parameter and show that it is possible to reach values significantly better than those obtained by a step index fibre.

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.

scholarly journals An Iterative Approach to Ill-Conditioned Optimal Portfolio Selection

2019 ◽  
Vol 56 (4) ◽  
pp. 773-794 ◽  
Author(s):  
Mårten Gulliksson ◽  
Stepan Mazur
Keyword(s):  
Covariance Matrix ◽  
Portfolio Selection ◽  
Numerical Study ◽  
Asset Returns ◽  
Positive Definite ◽  
Convergence Properties ◽  
Good Convergence ◽  
Optimal Portfolio Selection ◽  
Singular Covariance Matrix ◽  
Better Than

AbstractCovariance matrix of the asset returns plays an important role in the portfolio selection. A number of papers is focused on the case when the covariance matrix is positive definite. In this paper, we consider portfolio selection with a singular covariance matrix. We describe an iterative method based on a second order damped dynamical systems that solves the linear rank-deficient problem approximately. Since the solution is not unique, we suggest one numerical solution that can be chosen from the iterates that balances the size of portfolio and the risk. The numerical study confirms that the method has good convergence properties and gives a solution as good as or better than the solutions that are based on constrained least norm Moore–Penrose, Lasso, and naive equal-weighted approaches. Finally, we complement our result with an empirical study where we analyze a portfolio with actual returns listed in S&P 500 index.

Sign in / Sign up

Export Citation Format

Share Document