Flow of Microfluids in Converging Microchannels

2009 ◽  
Author(s):  
Nelson Macken ◽  
Jong Hsien Lim
Keyword(s):  
Reynolds Number ◽  
Fluorescence Microscopy ◽  
Cross Section ◽  
Cross Sections ◽  
Three Dimensional ◽  
Main Channel ◽  
Two Dimensional ◽  
Water Flows ◽  
The Third ◽  
Confocal Fluorescence

The interface between intersecting microfluidic multicomponent flow is investigated experimentally. Three microchannel configurations are studied. Each configuration has a main channel and an intersecting daughter channel. In two configurations, the channel cross sections are equal and square with the intersection either at 90 or 45 degrees. In the third configuration, the intersection is at 90 degrees, the cross sections are square and the daughter cross section is smaller than the main cross section. In the configurations with equal channel cross sections, microsphere solutions of 2, 4 and 7% spheres (by weight) are compared to each other as well as all water flows. Flow visualization is achieved using confocal fluorescence microscopy. A three-dimensional rendering of the location and shape of the interface is examined for a Reynolds number of approximately one. The presence of microspheres does not appear to strongly influence the location of the flow interface. For flows with equal cross section, the interface downstream of the junction is reasonably planer (two dimensional). Strong three-dimensional effects are shown for flows with unequal cross section.

Flow of Microsphere Solutions in Converging Microchannels

2008 ◽  
Author(s):  
Alexis B. Reedy ◽  
Nelson Macken
Keyword(s):  
Reynolds Number ◽  
Fluorescence Microscopy ◽  
Three Dimensional ◽  
Main Channel ◽  
Two Dimensional ◽  
Mixture Flow ◽  
Water Flows ◽  
Combined Flow ◽  
Flow Reynolds Number ◽  
Confocal Fluorescence

The interface between intersecting microfluidic multicomponent flow is investigated experimentally. The system studied has a main channel and an intersecting (at 90 degrees) daughter channel and the fluid is a water-microsphere mixture. Flow visualization is achieved using confocal fluorescence microscopy. Microsphere solutions of 2% and 4% spheres (by weight) are investigated and compared to each other as well as all water flows. A three-dimensional rendering of the location and shape of the interface at the junction for different flow ratios (daughter flow to total) is examined for a combined flow Reynolds number of approximately one. The interface downstream of the junction is reasonably planer (two-dimensional) and the presence of microspheres does not appear to strongly influence the location of the flow interface.

scholarly journals Membrane analogy for multi-material bars under torsion

2019 ◽  
Vol 475 (2225) ◽  
pp. 20190124 ◽  
Author(s):  
Laura Galuppi ◽  
Gianni Royer-Carfagni
Keyword(s):  
Finite Element ◽  
Cross Section ◽  
Cross Sections ◽  
Three Dimensional ◽  
Element Model ◽  
Elastic Problem ◽  
Two Dimensional ◽  
Torsion Problem ◽  
Linear Elastic ◽  
Physical Apparatus

Prandtl's membrane analogy for the torsion problem of prismatic homogeneous bars is extended to multi-material cross sections. The linear elastic problem is governed by the same equations describing the deformation of an inflated membrane, differently tensioned in regions that correspond to the domains hosting different materials in the bar cross section, in a way proportional to the inverse of the material shear modulus. Multi-connected cross sections correspond to materials with vanishing stiffness inside the holes, implying infinite tension in the corresponding portions of the membrane. To define the interface constrains that allow to apply such a state of prestress to the membrane, a physical apparatus is proposed, which can be numerically modelled with a two-dimensional mesh implementable in commercial finite-element model codes. This approach presents noteworthy advantages with respect to the three-dimensional modelling of the twisted bar.

scholarly journals Computational Study of Zigzag Spacer Design with Elliptical Cross-Section Filaments

2020 ◽  
Vol 307 ◽  
pp. 01047
Author(s):  
Gohar Shoukat ◽  
Farhan Ellahi ◽  
Muhammad Sajid ◽  
Emad Uddin
Keyword(s):  
Mass Transfer ◽  
Cross Section ◽  
Cross Sections ◽  
Computational Study ◽  
Flow Direction ◽  
Three Dimensional ◽  
Circular Cross Section ◽  
Two Dimensional ◽  
Permeate Flux ◽  
Elliptical Cross

The large energy consumption of membrane desalination process has encouraged researchers to explore different spacer designs using Computational Fluid Dynamics (CFD) for maximizing permeate per unit of energy consumed. In previous studies of zigzag spacer designs, the filaments are modeled as circular cross sections in a two-dimensional geometry under the assumption that the flow is oriented normal to the filaments. In this work, we consider the 45° orientation of the flow towards the three-dimensional zigzag spacer unit, which projects the circular cross section of the filament as elliptical in a simplified two-dimensional domain. OpenFOAM was used to simulate the mass transfer enhancement in a reverse-osmosis desalination unit employing spiral wound membranes lined with zigzag spacer filaments. Properties that impact the concentration polarization and hence permeate flux were analyzed in the domain with elliptical filaments as well as a domain with circular filaments to draw suitable comparisons. The range of variation in characteristic parameters across the domain between the two different configurations is determined. It was concluded that ignoring the elliptical projection of circular filaments to the flow direction, can introduce significant margin of error in the estimation of mass transfer coefficient.

Lattice-Boltzmann simulations of particles in non-zero-Reynolds-number flows

1999 ◽  
Vol 385 ◽  
pp. 41-62 ◽  
Author(s):  
DEWEI QI
Keyword(s):  
Reynolds Number ◽  
Cross Section ◽  
Lattice Boltzmann ◽  
Three Dimensional ◽  
Spherical Particles ◽  
Computational Results ◽  
Two Dimensional ◽  
Lattice Boltzmann Simulations ◽  
Boltzmann Method ◽  
Reynolds Number Flows

A lattice-Boltzmann method has been developed to simulate suspensions of both spherical and non-spherical particles in finite-Reynolds-number flows. The results for sedimentation of a single elliptical particle are shown to be in excellent agreement with the results of Huang, Hu & Joseph (1998) who used a finite-element method. Sedimentation of two-dimensional circular and rectangular particles in a two-dimensional channel and three-dimensional spherical particles in a tube with square cross-section is simulated. Computational results are consistent with experimentally observed phenomena, such as drafting, kissing and tumbling.

A Numerical Study on Squat of a Wigley Hull

2011 ◽  
Author(s):  
Mahmoud Alidadi ◽  
Sander Calisal
Keyword(s):  
Boundary Element Method ◽  
Cross Section ◽  
Cross Sections ◽  
Numerical Study ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Slender Body Theory ◽  
Flow Potential ◽  
Wigley Hull ◽  
Body Theory

A numerical study is conducted to calculate the squat for a wigley hull. An approach based on slender body theory is used to convert the three dimensional ship problem into a series of two dimensional problems in cross sections from bow to stern (solved sequentially in time). A boundary element method is used to compute the flow potential at every cross section. The ship squat is calculated from the pressure integration over the hull. Numerical results for the Wigley hull is presented and compared with the experimental results.

scholarly journals Processing of two-dimensional velocity fields for reconstructing three-dimensional flow patterns

2021 ◽  
Vol 2127 (1) ◽  
pp. 012031
Author(s):  
S Yu Belov
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Three Dimensional ◽  
Velocity Fields ◽  
Optical Methods ◽  
Two Dimensional ◽  
Three Dimensional Flow ◽  
Dimensional Flow ◽  
Optimal Type

Abstract The paper is concerned with the obtaining three-dimensional velocity fields of a gas or liquid flow based on the available cross-sections of this flow. The descriptions of the main optical methods for studying flows are designed to construct a cross-section of the observed process, but it would be much more informative to obtain information in the visualization not in the cross-section of a volume, but in this volume itself. The paper deals with obtaining three-dimensional flow velocity fields using various approximation methods. The method of estimating the most suitable approximating function is also given. The determination of the optimal type of approximation for the reconstruction of the three-dimensional velocity field was tested on an artificially created vortex.

Microstructure Evolution of Epitaxial (Ba, Sr) TiO3/ (001) HgO Thin Films

1994 ◽  
Vol 361 ◽  
Author(s):  
V.A. Alyoshin ◽  
E.V. Sviridov ◽  
V.I.M. Hukhortov ◽  
I.H. Zakharchenko ◽  
V.P. Dudkevich
Keyword(s):  
Thin Films ◽  
Cross Section ◽  
Microstructure Evolution ◽  
Three Dimensional ◽  
Gas Pressure ◽  
Smooth Surfaces ◽  
Two Dimensional ◽  
Surface Versus ◽  
Deposition Conditions

ABSTRACTSurface and cross-section relief evolution of ferroelectric epitaxial (Ba,Sr)TiO3 films rf-sputtered on (001) HgO crystal cle-avage surface versus the oxygen worKing gas pressure P and subst-rate temperature T were studied. Specific features of both three-dimensional and two-dimensional epitaxy mechanisms corresponding to various deposition conditions were revealed. Difference between low and high P-T-value 3D epitaxy was established. The deposition of films with mirror-smooth surfaces and perfect interfaces is shown to be possible.

Plane turbulent jets in a bounded fluid layer

1992 ◽  
Vol 241 ◽  
pp. 587-614 ◽  
Author(s):  
T. Dracos ◽  
M. Giger ◽  
G. H. Jirka
Keyword(s):  
Experimental Investigation ◽  
Cross Section ◽  
Fluid Layer ◽  
Three Dimensional ◽  
Turbulent Jets ◽  
Two Dimensional ◽  
Vortical Structures ◽  
Secondary Currents ◽  
Fluid Layers ◽  
Bounding Surfaces

An experimental investigation of plane turbulent jets in bounded fluid layers is presented. The development of the jet is regular up to a distance from the orifice of approximately twice the depth of the fluid layer. From there on to a distance of about ten times the depth, the flow is dominated by secondary currents. The velocity distribution over a cross-section of the jet becomes three-dimensional and the jet undergoes a constriction in the midplane and a widening near the bounding surfaces. Beyond a distance of approximately ten times the depth of the bounded fluid layer the secondary currents disappear and the jet starts to meander around its centreplane. Large vortical structures develop with axes perpendicular to the bounding surfaces of the fluid layer. With increasing distance the size of these structures increases by pairing. These features of the jet are associated with the development of quasi two-dimensional turbulence. It is shown that the secondary currents and the meandering do not significantly affect the spreading of the jet. The quasi-two-dimensional turbulence, however, developing in the meandering jet, significantly influences the mixing of entrained fluid.

Bifurcation Characteristics of Flows in Rectangular Sudden Expansion Channels

2005 ◽  
Author(s):  
Francine Battaglia ◽  
George Papadopoulos
Keyword(s):  
Reynolds Number ◽  
Laminar Flow ◽  
Critical Reynolds Number ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Expansion Ratio ◽  
Sudden Expansion ◽  
Two Dimensional ◽  
Effective Expansion ◽  
Three Dimensional Simulations

The effect of three-dimensionality on low Reynolds number flows past a symmetric sudden expansion in a channel was investigated. The geometric expansion ratio of in the current study was 2:1 and the aspect ratio was 6:1. Both experimental velocity measurements and two- and three-dimensional simulations for the flow along the centerplane of the rectangular duct are presented for Reynolds numbers in the range of 150 to 600. Comparison of the two-dimensional simulations with the experiments revealed that the simulations fail to capture completely the total expansion effect on the flow, which couples both geometric and hydrodynamic effects. To properly do so requires the definition of an effective expansion ratio, which is the ratio of the downstream and upstream hydraulic diameters and is therefore a function of both the expansion and aspect ratios. When the two-dimensional geometry was consistent with the effective expansion ratio, the new results agreed well with the three-dimensional simulations and the experiments. Furthermore, in the range of Reynolds numbers investigated, the laminar flow through the expansion underwent a symmetry-breaking bifurcation. The critical Reynolds number evaluated from the experiments and the simulations was compared to other values reported in the literature. Overall, side-wall proximity was found to enhance flow stability, helping to sustain laminar flow symmetry to higher Reynolds numbers in comparison to nominally two-dimensional double-expansion geometries. Lastly, and most importantly, when the logarithm of the critical Reynolds number from all these studies was plotted against the reciprocal of the effective expansion ratio, a linear trend emerged that uniquely captured the bifurcation dynamics of all symmetric double-sided planar expansions.

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