scholarly journals Mixing Performance of a Passive Micro-Mixer with Mixing Units Stacked in Cross Flow Direction

Micromachines ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1530
Author(s):  
Makhsuda Juraeva ◽  
Dong-Jin Kang
Keyword(s):  
Numerical Study ◽  
Volume Flow Rate ◽  
Flow Direction ◽  
Cross Flow ◽  
Reynolds Numbers ◽  
High Concentration ◽  
Mixing Performance ◽  
Wall Impingement ◽  
The Cross ◽  
Micro Mixer

A new passive micro-mixer with mixing units stacked in the cross flow direction was proposed, and its performance was evaluated numerically. The present micro-mixer consisted of eight mixing units. Each mixing unit had four baffles, and they were arranged alternatively in the cross flow and transverse direction. The mixing units were stacked in four different ways: one step, two step, four step, and eight step stacking. A numerical study was carried out for the Reynolds numbers from 0.5 to 50. The corresponding volume flow rate ranged from 6.33 μL/min to 633 μL/min. The mixing performance was analyzed in terms of the degree of mixing (DOM) and relative mixing energy cost (MEC). The numerical results showed a noticeable enhancement of the mixing performance compared with other micromixers. The mixing enhancement was achieved by two flow characteristics: baffle wall impingement by a stream of high concentration and swirl motion within the mixing unit. The baffle wall impingement by a stream of high concentration was observed throughout all Reynolds numbers. The swirl motion inside the mixing unit was observed in the cross flow direction, and became significant as the Reynolds number increased to larger than about five. The eight step stacking showed the best performance for Reynolds numbers larger than about two, while the two step stacking was better for Reynolds numbers less than about two.

scholarly journals Mixing Performance of a Cross-Channel Split-and-Recombine Micro-Mixer Combined with Mixing Cell

Micromachines ◽  
2020 ◽  
Vol 11 (7) ◽  
pp. 685
Author(s):  
Makhsuda Juraeva ◽  
Dong Jin Kang
Keyword(s):  
Molecular Diffusion ◽  
Numerical Study ◽  
Volume Flow Rate ◽  
Volume Flow ◽  
Mixing Enhancement ◽  
Mixing Performance ◽  
Two Fluids ◽  
Dean Vortex ◽  
Wide Range ◽  
Micro Mixer

A new cross-channel split-and-recombine (CC-SAR) micro-mixer was proposed, and its performance was demonstrated numerically. A numerical study was carried out over a wide range of volume flow rates from 3.1 μL/min to 826.8 μL/min. The corresponding Reynolds number ranges from 0.3 to 80. The present micro-mixer consists of four mixing units. Each mixing unit is constructed by combining one split-and-recombine (SAR) unit with a mixing cell. The mixing performance was analyzed in terms of the degree of mixing and relative mixing cost. All numerical results show that the present micro-mixer performs better than other micro-mixers based on SARs over a wide range of volume flow rate. The mixing enhancement is realized by a particular motion of vortex flow: the Dean vortex in the circular sub-channel and another vortex inside the mixing cell. The two vortex flows are generated on the different planes perpendicular to each other. They cause the two fluids to change their relative position as the fluids flow into the circular sub-channel of the SAR, eventually promoting violent mixing. High vorticity in the mixing cell elongates the flow interface between two fluids, and promotes mixing in the flow regime of molecular diffusion dominance.

Numerical Study on Mixing of Two Fluids With Modified Tesla Structure

2009 ◽  
Author(s):  
Shakhawat Hossain ◽  
Mubashshir Ahmad Ansari ◽  
Afzal Husain ◽  
Kwang-Yong Kim
Keyword(s):  
Vortical Structure ◽  
Numerical Study ◽  
Reynolds Numbers ◽  
The Other ◽  
Channel Width ◽  
Geometrical Parameters ◽  
Fluid Stream ◽  
Mixing Performance ◽  
Two Fluids ◽  
Wide Range

In this study, a parametric investigation on mixing of two fluids in a modified Tesla microchannel, has been preformed. Modified Tesla micromixer applies both flow separation and vortices string principles to enhance the mixing. The fluid stream splits into two sub-streams and one of them mixes with the other again at the exit of the Tesla unit. Analyses of mixing and flow field have been carried out for a wide range of Reynolds number from 0.05 to 40. Mixing performance and pressure drop characteristics with two geometrical parameters, i.e, ratio of the diffuser gap to channel width (h/w) and ratio of the curved gap to the channel width (s/w), have been analyzed at six different Reynolds numbers. The vortical structure of the flow has been analyzed to explain mixing performance. The sensitivity analysis reveals that mixing is more sensitive s/w, than the h/w.

scholarly journals Numerical Study on Heat and Mass Transfer of the Cross-flow Liquid Desiccant Regenerator

2017 ◽  
Vol 205 ◽  
pp. 2647-2654 ◽  
Author(s):  
Yang Li ◽  
Zhibo Fu ◽  
Xiaohu Yang ◽  
Lianying Zhang ◽  
Qunli Zhang ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Numerical Study ◽  
Cross Flow ◽  
Liquid Desiccant ◽  
The Cross

The Importance of Mode Number on In-Line Amplitude of Vortex-Induced Vibration of Flexible Cylinders

2008 ◽  
Author(s):  
Susan B. Swithenbank ◽  
Carl Martin Larsen
Keyword(s):  
Natural Frequencies ◽  
Flow Direction ◽  
Empirical Relationship ◽  
Cross Flow ◽  
Bending Stiffness ◽  
Mode Number ◽  
Flow Mode ◽  
Physical Parameters ◽  
Complex Data ◽  
The Cross

Most empirical codes for prediction of vortex-induced vibrations (VIV) has so far been limited to cross-flow response. The reason for this is that cross-flow amplitudes are normally larger that in-line amplitudes. Additionally the in-line response is considered to be driven by the cross-flow vibrations. However since the in-line frequency is twice the cross-flow frequency, fatigue damage from in-line vibrations may become as important and even exceed the damage from cross-flow vibrations. A way to predict in-line vibrations is to apply traditional methods that are used for cross-flow VIV and establish an empirical relationship between the cross-flow and in-line response. Previous work suggests that the ratio between the in-line and cross-flow amplitudes depends on the cross-flow mode number, Baarhom et al. (2004), but the empirical basis for this hypothesis is not strong. The motivation for the present work has been to verify or modify this hypothesis by extensive analysis of observed response. The present analysis uses complex data from experiments with wide variations in the physical parameters of the system, including length-to-diameter ratios from 82 to 4236, tension dominated natural frequencies and bending stiffness dominated natural frequencies, sub-critical and critical Reynolds numbers, different damping coefficients, uniform and sheared flows, standing wave and traveling wave vibrations, mode numbers from 1–25th, and different mass ratios. The conclusion from this work is that the cross-flow mode number is not the important parameter, but whether the frequency of vibration in the cross-flow direction is dominated by bending stiffness of tension.

Interference in a three-dimensional array of jets

2015 ◽  
Vol 26 (5) ◽  
pp. 795-819
Author(s):  
P. E. WESTWOOD ◽  
F. T. SMITH
Keyword(s):  
Cross Sections ◽  
Flow Direction ◽  
Three Dimensional ◽  
Cross Flow ◽  
Longitudinal Vortex ◽  
Cross Sectional ◽  
Dimensional Array ◽  
Unsteady Jets ◽  
The Cross ◽  
Jet Cross Sections

The theoretical investigation here of a three-dimensional array of jets of fluid (air guns) and their interference is motivated by applications to the food sorting industry especially. Three-dimensional motion without symmetry is addressed for arbitrary jet cross-sections and incident velocity profiles. Asymptotic analysis based on the comparatively long axial length scale of the configuration leads to a reduced longitudinal vortex system providing a slender flow model for the complete array response. Analytical and numerical studies, along with comparisons and asymptotic limits or checks, are presented for various cross-sectional shapes of nozzle and velocity inputs. The influences of swirl and of unsteady jets are examined. Substantial cross-flows are found to occur due to the interference. The flow solution is non-periodic in the cross-plane even if the nozzle array itself is periodic. The analysis shows that in general the bulk of the three-dimensional motion can be described simply in a cross-plane problem but the induced flow in the cross-plane is sensitively controlled by edge effects and incident conditions, a feature which applies to any of the array configurations examined. Interference readily alters the cross-flow direction and misdirects the jets. Design considerations centre on target positioning and jet swirling.

Three Dimensional Numerical Modelling of Staggered Tube Bundle Turbulent Crossflow in Duct

2005 ◽  
Author(s):  
Ahad Ramezanpour ◽  
Hassan Shirvani ◽  
Ramin Rahmani ◽  
Iraj Mirzaee
Keyword(s):  
Nusselt Number ◽  
Numerical Study ◽  
Tube Bundle ◽  
Three Dimensional ◽  
Cross Flow ◽  
Reynolds Numbers ◽  
Wall Function ◽  
Flat Plates ◽  
Geometrical Characteristics ◽  
Commercial Code

A numerical study has been conducted to investigate the three dimensional (3D) staggered tube bundle turbulent cross flow confined between two parallel flat plates using RNG k-ε model and standard wall function utilizing commercial code FLUENT. The maximum Reynolds numbers of 1000, 5000, and 50000 and the distance between plates of H = 3, 5, 10, 15, and 20 mm have been considered. The arrangement of the staggered tube bundle is fix with geometrical characteristics of Sn/D = 1.5 and Sp/D = 1.2 which has been found optimum in previous two-dimensional studies. The constant temperature of 360K on tubes, constant inlet flow and plates’ temperature of 300K have been set as the boundary conditions. The global Nusselt number, friction factor for the dissimilar Reynolds numbers, distance between plates, local Nusselt number and different angles on first and third tubes have been evaluated.

scholarly journals Design and Numerical Study of Micropump Based on Induced Electroosmotic Flow

2018 ◽  
Vol 2018 ◽  
pp. 1-6 ◽  
Author(s):  
Kai Zhang ◽  
Lengjun Jiang ◽  
Zhihan Gao ◽  
Changxiu Zhai ◽  
Weiwei Yan ◽  
...  
Keyword(s):  
Electroosmotic Flow ◽  
Stokes Equations ◽  
Numerical Study ◽  
Cross Flow ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Driving Mode ◽  
Electric Driving ◽  
Induced Charge ◽  
The Cross

Induced charge electroosmotic flow is a new electric driving mode. Based on the Navier–Stokes equations and the Poisson–Nernst–Planck (PNP) ion transport equations, the finite volume method is adopted to calculate the equations and boundary conditions of the induced charge electroosmotic flow. In this paper, the formula of the induced zeta potential of the polarized solid surface is proposed, and a UDF program suitable for the simulation of the induced charge electroosmotic is prepared according to this theory. At the same time, on the basis of this theory, a cross micropump driven by induced charge electroosmotic flow is designed, and the voltage, electric potential, charge density, and streamline of the induced electroosmotic micropump are obtained. Studies have shown that when the cross-shaped micropump is energized, in the center of the induction electrode near the formation of a dense electric double layer, there exist four symmetrical vortices at the four corners, and they push the solution towards both outlets; it can be found that the average velocity of the solution in the cross-flow microfluidic pump is nonlinear with the applied electric field, which maybe helpful for the practical application of induced electroosmotic flow in the field of micropump.

scholarly journals Investigation on the Coupling Effects between Flow and Fibers on Fiber-Reinforced Plastic (FRP) Injection Parts

Polymers ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2274
Author(s):  
Chao-Tsai Huang ◽  
Cheng-Hong Lai
Keyword(s):  
Coupling Effect ◽  
Flow Direction ◽  
Cross Flow ◽  
Orientation Distribution ◽  
Tensor Component ◽  
Fiber Reinforced ◽  
Orientation Tensor ◽  
Fiber Coupling ◽  
Fiber Orientation Distribution ◽  
The Cross

Glass or carbon fibers have been verified that can enhance the mechanical properties of the polymeric composite injection molding parts due to their orientation distribution. However, the interaction between flow and fiber is still not fully understood yet, especially for the flow–fiber coupling effect. In this study, we have tried to investigate the flow–fiber coupling effect on fiber reinforced plastics (FRP) injection parts utilizing a more complicated geometry system with three ASTM D638 specimens. The study methods include both numerical simulation and experimental observation. Results showed that in the presence of flow–fiber coupling effect, the melt flow front advancement presents some variation, specifically the “convex-flat-flat” pattern will change to a “convex-flat-concave” pattern. Furthermore, through the fiber orientation distribution (FOD) study, the flow–fiber coupling effect is not significant at the near gate region (RG). It might result from the strong shear force to repress the appearance of the flow–fiber interaction. However, at the end of filling region (ER), the flow–fiber coupling effect tries to diminish the flow direction orientation tensor component A11 and enhance the cross-flow orientation tensor component A22 simultaneously. It results in the dominance in the cross-flow direction at the ER. This orientation distribution behavior variation has been verified using a micro-computerized tomography (micro-CT) scan and image analysis technology.

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