scholarly journals Pattern Transition on Inertial Focusing of Neutrally Buoyant Particles Suspended in Rectangular Duct Flows

Micromachines ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 1242
Author(s):  
Hiroshi Yamashita ◽  
Takeshi Akinaga ◽  
Masako Sugihara-Seki
Keyword(s):  
Cross Section ◽  
Lift Force ◽  
Pitchfork Bifurcation ◽  
Blockage Ratio ◽  
Duct Flow ◽  
Rectangular Duct ◽  
Inertial Focusing ◽  
Particle Focusing ◽  
Wide Range ◽  
The Cross

The continuous separation and filtration of particles immersed in fluid flows are important interests in various applications. Although the inertial focusing of particles suspended in a duct flow is promising in microfluidics, predicting the focusing positions depending on the parameters, such as the shape of the duct cross-section and the Reynolds number (Re) has not been achieved owing to the diversity of the inertial-focusing phenomena. In this study, we aimed to elucidate the variation of the inertial focusing depending on Re in rectangular duct flows. We performed a numerical simulation of the lift force exerted on a spherical particle flowing in a rectangular duct and determined the lift-force map within the duct cross-section over a wide range of Re. We estimated the particle trajectories based on the lift map and Stokes drag, and identified the particle-focusing points appeared in the cross-section. For an aspect ratio of the duct cross-section of 2, we found that the blockage ratio changes transition structure of particle focusing. For blockage ratios smaller than 0.3, particles focus near the centres of the long sides of the cross-section at low Re and near the centres of both the long and short sides at relatively higher Re. This transition is expressed as a subcritical pitchfork bifurcation. For blockage ratio larger than 0.3, another focusing pattern appears between these two focusing regimes, where particles are focused on the centres of the long sides and at intermediate positions near the corners. Thus, there are three regimes; the transition between adjacent regimes at lower Re is found to be expressed as a saddle-node bifurcation and the other transition as a supercritical pitchfork bifurcation.

scholarly journals Effects of small boundary perturbation on the MHD duct flow

2017 ◽  
Vol 44 (1) ◽  
pp. 83-101 ◽  
Author(s):  
Ulavathi Mahabaleshwar ◽  
Igor Pazanin ◽  
Marko Radulovic ◽  
Francisco Suárez-Grau
Keyword(s):  
Magnetic Field ◽  
Asymptotic Solution ◽  
Asymptotic Analysis ◽  
Cross Section ◽  
Transverse Magnetic ◽  
Boundary Perturbation ◽  
Duct Flow ◽  
Rectangular Duct ◽  
Induced Magnetic Field ◽  
Explicit Formulae

In this paper, we investigate the effects of small boundary perturbation on the laminar motion of a conducting fluid in a rectangular duct under applied transverse magnetic field. A small boundary perturbation of magnitude ? is applied on cross-section of the duct. Using the asymptotic analysis with respect to ?, we derive the effective model given by the explicit formulae for the velocity and induced magnetic field. Numerical results are provided confirming that the considered perturbation has nonlocal impact on the asymptotic solution.

scholarly journals Optimization of Geometrical Parameters of Hollow-core Slabs by Formwork-free Shaping for Construction in Seismic Areas

2020 ◽  
Vol 8 (6) ◽  
pp. 4973-4977
Keyword(s):  
Cross Section ◽  
High Strength ◽  
Geometrical Parameters ◽  
Hollow Core ◽  
Constructive Solution ◽  
Industrial Buildings ◽  
Operational Load ◽  
Wide Range ◽  
Hollow Core Slab ◽  
The Cross

The building norms and standards of Uzbekistan on the reinforced concrete structures do not regulate the design of hollow-core slabs of formwork-free shaping, reinforced with prestressed wire reinforcement. The manufacturing technology of such slabs allows creating a wide range of products that increase the possibility of their use in various structural systems in residential, civil and industrial buildings, but in non-seismic areas only. The aim of this work is to develop a constructive solution for the cross section of a prestressed hollow-core floor slab of bench formwork-free shaping, reinforced with high-strength wire reinforcement, in order to create a wide range of products intended for construction in seismic areas. To achieve the goal, the problem of determining the optimal combination of height and configuration parameters of the cross section of such a slab is solved, meeting the normalized operational requirements and limitations of earthquake-resistant building standards. The main variable parameters are the height and the void degree of the section, characterized by the size and shape of voids. In calculating the cross-section of a hollow-core slab when substantiating the theoretical basis for the calculation, the cross section is reduced to the equivalent I-section. As a result of research, a constructive solution was developed for the slab cross section of the maximum parameter values (the span, operational load) set by the customer. The parameters of the slab cross-section are: the height 190 mm, the hollowness 38%, the height of the upper thickened flange (compared with the height of the lower flange) of the given section is 0.27h, the height of the lower flange is 0.17h, the reduced (total) thickness of all ribs “b” is 0.32 of the width of the upper flange. The voids in the section along the height of the slab are arranged asymmetrically. A patent for a utility model has been received for the proposed constructive solution of the slab cross section.

scholarly journals Optimized CNT-PDMS Flexible Composite for Attachable Health-Care Device

Sensors ◽  
2020 ◽  
Vol 20 (16) ◽  
pp. 4523 ◽  
Author(s):  
Jian Du ◽  
Li Wang ◽  
Yanbin Shi ◽  
Feng Zhang ◽  
Shiheng Hu ◽  
...  
Keyword(s):  
Composite Material ◽  
Percolation Threshold ◽  
Young’S Modulus ◽  
Cross Section ◽  
Young's Modulus ◽  
Large Strain ◽  
Weight Ratio ◽  
Linear Range ◽  
Wide Range ◽  
The Cross

The CNT-PDMS composite has been widely adopted in flexible devices due to its high elasticity, piezoresistivity, and biocompatibility. In a wide range of applications, CNT-PDMS composite sensors were used for resistive strain measurement. Accordingly, the percolation threshold 2%~4% of the CNT weight ratio in the CNT-PDMS composite was commonly selected, which is expected to achieve the optimized piezoresistive sensitivity. However, the linear range around the percolation threshold weight ratio (2%~4%) limits its application in a stable output of large strain (>20%). Therefore, comprehensive understanding of the electromechanical, mechanical, and electrical properties for the CNT-PDMS composite with different CNT weight ratios was expected. In this paper, a systematic study was conducted on the piezoresistivity, Young’s modulus, conductivity, impedance, and the cross-section morphology of different CNT weight ratios (1 to 10 wt%) of the CNT-PDMS composite material. It was experimentally observed that the piezo-resistive sensitivity of CNT-PDMS negatively correlated with the increase in the CNT weight ratio. However, the electrical conductivity, Young’s modulus, tensile strength, and the linear range of piezoresistive response of the CNT-PDMS composite positively correlated with the increase in CNT weight ratio. Furthermore, the mechanism of these phenomena was analyzed through the cross-section morphology of the CNT-PDMS composite material by using SEM imaging. From this analysis, a guideline was proposed for large strain (40%) measurement applications (e.g., motion monitoring of the human body of the finger, arm, foot, etc.), the CNT weight ratio 8 wt% was suggested to achieve the best piezoresistive sensitivity in the linear range.

A Microchannel With Repeated Sharp Corners for Single Stream Particle Focusing

2014 ◽  
Author(s):  
Liangliang Fan ◽  
Xukun He ◽  
Liang Zhao ◽  
Yu Han ◽  
Jiang Zhe
Keyword(s):  
Centrifugal Force ◽  
High Throughput ◽  
Flow Rate ◽  
Lift Force ◽  
Channel Wall ◽  
Sharp Corner ◽  
Force Effect ◽  
Particle Focusing ◽  
Wide Range ◽  
Sharp Corners

A new microfluidic device for fast and high throughput microparticle focusing is reported. The particle focusing is based on the combination of inertial lift force effect and centrifugal force effect generated in a microchannel with a series of repeated sharp corners on one side of the channel wall. The inertial lift force effect induces two focused particles streams in the microchannel, and the centrifugal force generated at the sharp corner structures tends to drive the particles laterally away from the corner. With the use of a series of the repeated, sharp corner structures, a single and highly focused particle stream was achieved near the straight channel wall at a wide range of flow rates. In comparison to other hydrodynamic particle focusing methods, this method is less sensitive to the flow rate and can work at a higher flow rate (high throughput). With its simple structure and operation, and high throughput, this method can be potentially used in microparticle focusing processes in a variety of lab-on-a chip applications.

scholarly journals Cross sections of electron collisions with noble gases atoms

2021 ◽  
pp. 11-16
Author(s):  
Rusudan Golyatina ◽  
Sergei Maiorov
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Noble Gas ◽  
Empirical Formulas ◽  
Electron Collisions ◽  
Wide Range ◽  
Analytical Formulas ◽  
The Cross ◽  
Approximation Coefficients ◽  
Ionization Cross Sections

Consideration is given to the analysis of data on the cross sections of elastic and inelastic col-lisions of electrons with noble gas atoms. The transport (diffusion) cross section, the excita-tion and ionization cross sections are studied. For the selected sets of experimental and theo-retical data, optimal analytical formulas are found and approximation coefficients are select-ed for them. The obtained semi-empirical formulas allow us to reproduce the cross section values in a wide range of collision energies from 0.001 to 10000 eV with an accuracy of sev-eral percent.

High-throughput particle focusing and separation in split-recombination channel

2022 ◽  
Vol 32 (2) ◽  
pp. 025007
Author(s):  
Shuang Chen ◽  
Zongqian Shi ◽  
Jiajia Sun ◽  
Shenli Jia ◽  
Mingjie Zhong ◽  
...  
Keyword(s):  
High Throughput ◽  
Lift Force ◽  
Curvature Radius ◽  
Straight Channel ◽  
Geometrical Structures ◽  
Inertial Focusing ◽  
Particle Focusing ◽  
Drag Forces ◽  
Recombination Channel ◽  
Flow Drag

Abstract Inertial microfluidic has been widely applied to manipulate particles or bio-sample based on the inertial lift force and Dean Vortices. This technology provides significant advantages over conventional technologies, including simple structure, high throughput and freedom from an external field. Among many inertial microfluidic systems, the straight microchannel is commonly used to produce inertial focusing, which is a phenomenon that particles or cells are aligned and separated based on their size under the influence of inertial lift force. Besides the inertial lift force, flow drag forces induced by the geometrical structures of microchannel can also affect particle focusing. Herein, a split-recombination microchannel, consisting of curved and straight channels, is proposed to focus and separate particles at high flow rate. As compared with the straight channel, the particle focusing in the split-recombination channel is greatly improved, which results from the combined effects of the inertial lift force, the curvature-induced Dean drag force and the structure of split and recombination. Moreover, the distribution of different-sized particles in designed microchannel is investigated. The results indicate that the proposed microchannel not only enhances the particle focusing but also enables the separation of different-sized particles with high throughput. Finally, it is discovered that the larger length of straight channel and curvature radius of curved channel can result in a more efficient particle separation. Another important feature of designed split-recombination microchannel is that it can be arranged in parallel to handle large-volume samples, holding great potential in lab-on-a-chip applications.

scholarly journals Electron scattering cross-sections for particle transport modeling in a weakly ionized air plasma

2021 ◽  
Vol 51 ◽  
pp. 96-111
Author(s):  
Vasily Sergeevich Zakharov ◽  
Mikhail Evgenievich Zhukovskiy ◽  
Sergey Vasilievich Zakharov ◽  
Mikhail Borisovich Markov
Keyword(s):  
Elastic Scattering ◽  
Cross Section ◽  
Electron Scattering ◽  
Cross Sections ◽  
Electron Interaction ◽  
Inelastic Electron ◽  
Neutral Atoms ◽  
Hartree Fock ◽  
Wide Range ◽  
The Cross

Data on processes of electron scattering on ions and neutral atoms are required in fundamental studies and in applied research in such fields as astro- and laser physics, low density plasma simulations, kinetic modeling etc. Experimental and computational data on elastic and inelastic electron scattering in a wide range of electron energies is available mostly for the electron interaction with neutral atoms, but are very limited for the scattering on ions, notably for elastic processes. In present work the calculational approaches for the cross-section computation of electron elastic and inelastic scattering on neutral atoms and ions are considered. The atomic and ion properties obtained in quantum-statistical Hartree-Fock-Slater model are used in the direct computation of electron elastic scattering and ionization cross-sections by a partial waves method, semiclassical and distorted-wave approximations. Calculated cross-sections for elastic scattering on nitrogen and oxygen atoms and ions, and electron ionisation cross-sections are compared with the available experimental data and widely used approximations and propose consistent results. Considering applicability of Hartree-Fock-Slater model in wide scope of temperatures and densities, such approach to the cross-section calculation can be used in a broad range of energies and ion charges.

scholarly journals XVII. The complete system of the periods of a hollow vortex ring

1895 ◽  
Vol 186 ◽  
pp. 603-619 ◽  
Keyword(s):  
Kinetic Theory ◽  
Vortex Ring ◽  
Cross Section ◽  
Steady Motion ◽  
Dynamical Theory ◽  
Vortex Theory ◽  
Wide Range ◽  
The Cross ◽  
Hollow Vortex ◽  
The Stability

According to the vortex theory of matter, atoms consist of vortex rings in an infinite perfect liquid, the æther. These rings may be either hollow or filled with otating liquid. The cross section of the hollow or rotating core is in the simplest ase small and the ring is circular. Such vortices have been investigated. It has been hown that they can exist, and that they are stable for certain types of deformation, in this paper the stability of the hollow vortex ring is investigated further, with a view to proving that it is stable for all small deformations of its surface. An attempt also made to make the vortex theory of matter agree with the kinetic theory of ases as regards the relation between the velocity and the energy of an atom. On he latter theory the energy of an atom varies as the square of its velocity, while on he former theory the energy decreases as the velocity increases. As the two theories liffer on a fundamental point, while the consequences of the kinetic theory agree over wide range with experiment, those of the vortex theory are likely to be in discrepancy therewith. However, no account has been taken of the electric change which an atom must hold if electrolysis is to be explained. This electrification will evidently alter the relation between the energy and the velocity. The nature of the change thus produced is here discussed for the case of a hollow vortex, the surface of which behaves as a conductor of electricity, a representation which is dynamically realised by the theory of a rotationally-elastic fluid æther developed in Mr. Larmor’s paper, “A Dynamical Theory of the Electric and Luminiferous Medium.” The small oscillations also are worked out with a view to the discussion of the stability of an electrified vortex. 2. The velocity of translation of the vortex in its steady motion is constant and perpendicular to its plane. By impressing on the whole liquid a velocity equal and opposite to this, the hollow is reduced to rest. Since the cross section of the hollow is small, any small length of it may be regarded as cylindrical. A cylindrical vortex must, by reason of symmetry, have its cross section a circle, so that the cross section of the hollow of the annular vortex is approximately circular, and the hollow itself approximately a tore.

scholarly journals Systematics of Spallation Yields

1966 ◽  
Vol 21 (7) ◽  
pp. 1027-1041 ◽  
Author(s):  
G. Rudstam
Keyword(s):  
Cross Section ◽  
Experimental Conditions ◽  
Wide Range ◽  
Cross Section Formula ◽  
The Cross ◽  
Cross Section Distribution ◽  
Fair Degree

Available experimental spallation data have been used to construct a five-parameter formula describing the cross-section distribution for a wide range of experimental conditions with a fair degree of accuracy. The application of the cross-section formula to different fields of research is indicated.

scholarly journals The effects of curvature on sheared turbulence

1992 ◽  
Vol 237 ◽  
pp. 569-603 ◽  
Author(s):  
A. G. L. Holloway ◽  
S. Tavoularis
Keyword(s):  
Cross Section ◽  
Rectangular Cross Section ◽  
Radius Of Curvature ◽  
Rectangular Duct ◽  
Statistical Homogeneity ◽  
Wide Range ◽  
Parallel Shear Flows ◽  
The Mean ◽  
Centreline Velocity ◽  
Approximate Expressions

The present experiments are an extension of previous studies on nearly homogeneous, parallel, shear flows and represent an attempt to study the effects of curvature on sheared turbulence in relative isolation from wall and entrainment effects. Uniformly sheared turbulence was allowed to reach a state of transverse statistical homogeneity in a straight rectangular duct: it was then passed into a curved duct, also of rectangular cross-section. The near homogeneity of the turbulence and the near uniformity of the shear were preserved. In the present experiments, the parameter S = (Uc/Rc)(dU/dn) spanned a wide range, from approximately -0.50 to over 1.0 (Uc is the centreline velocity, dU/dn the mean shear and Rc the radius of curvature on the centreline of the duct). Variation of S was achieved by using two curved tunnel sections as well as by adjusting the shear. Measurements indicate that the growth of the turbulent stresses and lengthscales was enhanced for S < 0 and suppressed for S > 0. For S > 0.05, the stresses decayed. In cases where sufficiently large total strain was achieved, the stresses seemed to grow or decay roughly exponentially and to develop in a quasi-self-preserving manner. The magnitude of the dimensionless shear stress decreased monotonically with increasing S, while, for sufficiently large positive values of S, this quantity reversed sign, to achieve the same sense as the mean shear. Measurements of the integral lengthscales and the Taylor microscales are presented and their dependence upon curvature discussed. The results in ‘mildly curved’ flows are used to derive approximate expressions for the dependence upon S of the various terms in the Reynolds stress equations, including the pressure-strain rate covariance tensor.

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