Statistical homogenization for assemblies of elliptical grains: effect of the aspect ratio and particle orientation

2004 ◽  
Vol 41 (21) ◽  
pp. 5837-5849 ◽  
Author(s):  
Fabrice Emeriault ◽  
Cécile Claquin
Keyword(s):  
Aspect Ratio ◽  
Particle Orientation ◽  
Statistical Homogenization

High-frequency viscosity of a dilute suspension of elongated particles in a linear shear flow between two walls

2014 ◽  
Vol 764 ◽  
pp. 133-147 ◽  
Author(s):  
François Feuillebois ◽  
Maria L. Ekiel-Jeżewska ◽  
Eligiusz Wajnryb ◽  
Antoine Sellier ◽  
Jerzy Bławzdziewicz
Keyword(s):  
Aspect Ratio ◽  
Shear Flow ◽  
Intrinsic Viscosity ◽  
Effective Viscosity ◽  
Geometric Constraints ◽  
Particle Orientation ◽  
Hydrodynamic Coupling ◽  
Linear Shear ◽  
Dilute Suspension ◽  
Particle Length

AbstractA general expression for the effective viscosity of a dilute suspension of arbitrary-shaped particles in linear shear flow between two parallel walls is derived in terms of the induced stresslets on particles. This formula is applied to $N$-bead rods and to prolate spheroids with the same length, aspect ratio and volume. The effective viscosity of non-Brownian particles in a periodic shear flow is considered here. The oscillating frequency is high enough for the particle orientation and centre-of-mass distribution to be practically frozen, yet small enough for the flow to be quasi-steady. It is known that for spheres, the intrinsic viscosity $[{\it\mu}]$ increases monotonically when the distance $H$ between the walls is decreased. The dependence is more complex for both types of elongated particles. Three regimes are theoretically predicted here: (i) a ‘weakly confined’ regime (for $H>l$, where $l$ is the particle length), where $[{\it\mu}]$ is slightly larger for smaller $H$; (ii) a ‘semi-confined’ regime, when $H$ becomes smaller than $l$, where $[{\it\mu}]$ rapidly decreases since the geometric constraints eliminate particle orientations corresponding to the largest stresslets; (iii) a ‘strongly confined’ regime when $H$ becomes smaller than 2–3 particle widths $d$, where $[{\it\mu}]$ rapidly increases owing to the strong hydrodynamic coupling with the walls. In addition, for sufficiently slender particles (with aspect ratio larger than 5–6) there is a domain of narrow gaps for which the intrinsic viscosity is smaller than that in unbounded fluid.

scholarly journals A 2D numerical study of the effect of particle shape and orientation on resistivity in shallow formations

Geophysics ◽  
2007 ◽  
Vol 72 (1) ◽  
pp. F9-F17 ◽  
Author(s):  
Etienne Rey ◽  
Denis Jongmans
Keyword(s):  
Aspect Ratio ◽  
Particle Shape ◽  
Numerical Study ◽  
Experimental Studies ◽  
Theoretical Models ◽  
Particle Orientation ◽  
Effective Resistivity ◽  
The Matrix ◽  
The Difference ◽  
Geotechnical Tests

Surficial heterogeneous soils such as till, alluvial fans, or slope deposits are difficult to characterize by geotechnical tests because of the presence of decimeter- to meter-sized pebbles or rocks. The effective resistivity of such two-component media composed of a percentage of resistive particles embedded in a conductive matrix is given by the Bussian’s equation. The application of this equation allows the concentration of resistive particles to be determined if the resistivity values of each component and of the mixture, as well as the cementation exponent [Formula: see text], are known. However, previous theoretical and experimental studies have shown that the effective resistivity is affected by the shape of the particles. The objective of this study is to numerically determine the 2D effects of particle shape and orientation on the resistivity. Two configurations have been considered in the finite element (FE) modeling: laboratory-like measurements and field layout. For circular particles, the numerical results fit the Bussian’s equation with an exponent [Formula: see text] of 2. Aligned elongated particles induce an anisotropy which can raise or diminish the exponent [Formula: see text], depending on the particle orientation and the tortuosity of the current paths. Field experiment simulations showed that [Formula: see text] varies between 2.5 and 3.1 for an aspect ratio of 5 and that anisotropy resulting from the particle shape has little effect ([Formula: see text] close to 2) when this ratio is lower than 2.5. This increase of [Formula: see text] with the aspect ratio is in agreement with both theoretical models and experimental studies. For laboratory measurement simulations, [Formula: see text] values vary between 1.3 and 4 for a particle aspect ratio of 5, whatever the resistivity contrast between the particles and the matrix. The difference in results between the two configurations is explained by the paradox of anisotropy.

scholarly journals Distribution and Deposition of Cylindrical Nanoparticles in a Turbulent Pipe Flow

2021 ◽  
Vol 11 (3) ◽  
pp. 962
Author(s):  
Wenqian Lin ◽  
Ruifang Shi ◽  
Jianzhong Lin
Keyword(s):  
Reynolds Number ◽  
Aspect Ratio ◽  
Pipe Flow ◽  
Flow Direction ◽  
Numerical Data ◽  
Turbulent Pipe Flow ◽  
Particle Orientation ◽  
Wall Region ◽  
Pipe Length ◽  
Particle Aspect Ratio

Distribution and deposition of cylindrical nanoparticles in a turbulent pipe flow are investigated numerically. The equations of turbulent flow including the effect of particles are solved together with the mean equations of the particle number density and the probability density function for particle orientation including the combined effect of Brownian and turbulent diffusion. The results show that the distribution of the particle concentration on the cross-section becomes non-uniform along the flow direction, and the non-uniformity is reduced with the increases of the particle aspect ratio and Reynolds number. More and more particles will align with their major axis near to the flow direction, and this phenomenon becomes more obvious with increasing the particle aspect ratio and with decreasing the Reynolds number. The particles in the near-wall region are aligned with the flow direction obviously, and only a slight preferential orientation is observed in the vicinity of pipe’s center. The penetration efficiency of particle decreases with increasing the particle aspect ratio, Reynolds number and pipe length-to-diameter ratio. Finally, the relationship between the penetration efficiency of particle and related synthetic parameters is established based on the numerical data.

Characteristic Geometry and Diffraction Contrast of Dispersed ThO2 Crystals

1969 ◽  
Vol 27 ◽  
pp. 168-169
Author(s):  
R. J. Horylev ◽  
L. E. Murr
Keyword(s):  
Dark Field ◽  
Particle Orientation ◽  
Contrast Effects ◽  
Strain Fields ◽  
Diffraction Contrast ◽  
Dispersed Particles ◽  
Field Electron Microscopy ◽  
Dark Field Electron ◽  
Particle Images ◽  
Diffraction Effects

Smith has shown by dark-field electron microscopy of extracted ThO2 particles from TD-nickel (2% ThO2) that they possess single crystal characteristics. It is generally assumed that these particle dispersions are incoherent. However, some diffraction effects associated with the particle images appeared to be similar to coherency strain fields. The present work will demonstrate conclusively that ThO2 dispersed particles in TD-nickel (2% ThO2) and TD-NiCr (2% ThO2, 20% Cr, Ni) are single crystals. Moreover, the diffraction contrast effects are extinction fringes. That is, these effects arise because of the particle orientation with respect to the electron beam and the extinction conditions for various operating reflections The particles are in fact incoherent.

New challenges to image processing posed by cryo-Electron microscopy of single particles

1991 ◽  
Vol 49 ◽  
pp. 422-423
Author(s):  
Joachim Frank
Keyword(s):  
Electron Microscopy ◽  
Phase Contrast ◽  
Particle Orientation ◽  
Single Particles ◽  
Contrast Transfer Function ◽  
Virtual Absence ◽  
Cryo Electron Microscopy ◽  
Spatial Frequencies ◽  
New Challenges ◽  
Particle Images

Compared with images of negatively stained single particle specimens, those obtained by cryo-electron microscopy have the following new features: (a) higher “signal” variability due to a higher variability of particle orientation; (b) reduced signal/noise ratio (S/N); (c) virtual absence of low-spatial-frequency information related to elastic scattering, due to the properties of the phase contrast transfer function (PCTF); and (d) reduced resolution due to the efforts of the microscopist to boost the PCTF at low spatial frequencies, in his attempt to obtain recognizable particle images.

Modification of MnS inclusion by tellurium in 38MnVS6 micro-alloyed steel

2020 ◽  
Vol 117 (6) ◽  
pp. 615
Author(s):  
Ping Shen ◽  
Lei Zhou ◽  
Qiankun Yang ◽  
Zhiqi Zeng ◽  
Kenan Ai ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Aspect Ratio ◽  
Strong Influence ◽  
Experimental Results ◽  
Alloyed Steel ◽  
Equivalent Diameter ◽  
Small Aspect Ratio ◽  
Steel Quality ◽  
Eds Analysis ◽  
Micro Alloyed Steel

In 38MnVS6 steel, the morphology of sulfide inclusion has a strong influence on the fatigue life and machinability of the steel. In most cases, the MnS inclusions show strip morphology after rolling, which significantly affects the steel quality. Usually, the MnS inclusion with a spherical morphology is the best morphology for the steel quality. In the present work, tellurium was applied to 38MnVS6 micro-alloyed steel to control the MnS inclusion. Trace tellurium was added into 38MnVS6 steel and the effect of Te on the morphology, composition, size and distribution of MnS inclusions were investigated. Experimental results show that with the increase of Te content, the equivalent diameter and the aspect ratio of inclusion decrease strikingly, and the number of inclusions with small aspect ratio increases. The inclusions are dissociated and spherized. The SEM-EDS analysis indicates that the trace Te mainly dissolves in MnS inclusion. Once the MnS is saturated with Te, MnTe starts to generate and wraps MnS. The critical Te/S value for the formation of MnTe in the 38MnV6 steel is determined to be approximately 0.075. With the increase of Te/S ratio, the aspect ratio of MnS inclusion decreases and gradually reaches a constant level. The Te/S value in the 38MnVS6 steel corresponding to the change of aspect ratio from decreasing to constant ranges from 0.096 to 0.255. This is most likely to be caused by the saturation of Te in the MnS inclusion. After adding Te in the steel, rod-like MnS inclusion is modified to small inclusion and the smaller the MnS inclusion, the lower the aspect ratio.

PENINGKATAN KEMAMPUAN GURU BAHASA INDONESIA DALAM MENYUSUN RENCANA PROGRAM PEMBELAJARAN (RPP) SDN 015 PAGARAN TAPAH DARUSSALAM MELALUI METODE PEMBERIAN TUGAS

2017 ◽  
Vol 5 (3) ◽  
pp. 713
Author(s):  
Mukhlis '
Keyword(s):  
Aspect Ratio ◽  
Duty Cycle ◽  
Lesson Plans ◽  
Learning Program ◽  
School Subjects ◽  
Bahasa Indonesia

Based on the observation of some teachers found the symptoms as follows: the lack of abilityof Indonesian teachers in designing learning program (RPP), the learning device is only usedas a supplement and not to the needs of teaching, most teachers again if asked the lessonanswered not have or has not been made. The purpose of this research is to improve theability of Indonesian teachers in designing learning program (RPP) at SDN 015 PagaranTapah Darussalam through the method of administration tasks. This type of research is actionresearch school. Subjects in this study were teachers Indonesian as many as 12 people. Basedon the analysis and discussion can be concluded that the method of administration tasks canimprove the ability of Indonesian teachers in making learning device in SDN 015 PagaranTapah Darussalam through the method of administration tasks. Under these conditions, thelevel of acceptance of teachers increased. The aspect ratio capability Indonesian teachers inpreparing lesson plans through the provision of duty cycle I and II of the increase from 56%and the second cycle to 79%.

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