scholarly journals Contribution of Particle–Wall Distance and Rotational Motion of a Single Confined Elliptical Particle to the Effective Viscosity in Pressure-Driven Plane Poiseuille Flows

2021 ◽  
Vol 11 (15) ◽  
pp. 6727
Author(s):  
Misa Kawaguchi ◽  
Tomohiro Fukui ◽  
Koji Morinishi
Keyword(s):  
Aspect Ratio ◽  
Temporal Variation ◽  
Rotational Motion ◽  
Equilibrium Position ◽  
Particle Shape ◽  
Effective Viscosity ◽  
Relative Viscosity ◽  
Suspended Particles ◽  
Inertial Migration ◽  
Wall Distance

Rheological properties of the suspension flow, especially effective viscosity, partly depend on spatial arrangement and motion of suspended particles. It is important to consider effective viscosity from the microscopic point of view. For elliptical particles, the equilibrium position of inertial migration in confined state is unclear, and there are few studies on the relationship between dynamics of suspended particles and induced local effective viscosity distribution. Contribution of a single circular or elliptical particle flowing between parallel plates to the effective viscosity was studied, focusing on the particle–wall distance and particle rotational motion using the two-dimensional regularized lattice Boltzmann method and virtual flux method. As a result, confinement effects of the elliptical particle on the equilibrium position of inertial migration were summarized using three definitions of confinement. In addition, the effects of particle shape (aspect ratio and confinement) on the effective viscosity were assessed focusing on the particle–wall distance. The contribution of particle shape to the effective viscosity was found to be enhanced when the particle flowed near the wall. Focusing on the spatial and temporal variation of relative viscosity evaluated from wall shear stress, it was found that the spatial variation of the local relative viscosity was larger than temporal variation regardless of the aspect ratio and particle–wall distance.

Temporal variation of suspended particles (TSP, PM10, and PM2.5) and chemical composition of PM10 in a site at the coast of the Gulf of Mexico

2019 ◽  
Vol 12 (11) ◽  
pp. 1267-1277 ◽  
Author(s):  
Alberto A. Espinosa ◽  
Javier Miranda ◽  
Enrique Hernández ◽  
Javier Reyes ◽  
Ana L. Alarcón ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Gulf Of Mexico ◽  
Temporal Variation ◽  
Suspended Particles ◽  
Pm10 And Pm2.5 ◽  
A Site

scholarly journals Atmospheric Ice Particle Shape Estimates from Polarimetric Radar Measurements and In Situ Observations

2017 ◽  
Vol 34 (12) ◽  
pp. 2569-2587 ◽  
Author(s):  
Sergey Y. Matrosov ◽  
Carl G. Schmitt ◽  
Maximilian Maahn ◽  
Gijs de Boer
Keyword(s):  
Aspect Ratio ◽  
Particle Shape ◽  
Characteristic Size ◽  
In Situ Measurements ◽  
Department Of Energy ◽  
Depolarization Ratio ◽  
Suggested Approach ◽  
Aspect Ratios ◽  
Radar Measurements

AbstractA remote sensing approach to retrieve the degree of nonsphericity of ice hydrometeors using scanning polarimetric Ka-band radar measurements from a U.S. Department of Energy Atmospheric Radiation Measurement (ARM) Program cloud radar operated in an alternate transmission–simultaneous reception mode is introduced. Nonsphericity is characterized by aspect ratios representing the ratios of particle minor-to-major dimensions. The approach is based on the use of a circular depolarization ratio (CDR) proxy reconstructed from differential reflectivity ZDR and copolar correlation coefficient ρhυ linear polarization measurements. Essentially combining information contained in ZDR and ρhυ, CDR-based retrievals of aspect ratios are fairly insensitive to hydrometeor orientation if measurements are performed at elevation angles of around 40°–50°. The suggested approach is applied to data collected using the third ARM Mobile Facility (AMF3), deployed to Oliktok Point, Alaska. Aspect ratio retrievals were also performed using ZDR measurements that are more strongly (compared to CDR) influenced by hydrometeor orientation. The results of radar-based retrievals are compared with in situ measurements from the tethered balloon system (TBS)-based video ice particle sampler and the ground-based multiangle snowflake camera. The observed ice hydrometeors were predominantly irregular-shaped ice crystals and aggregates, with aspect ratios varying between approximately 0.3 and 0.8. The retrievals assume that particle bulk density influencing (besides the particle shape) observed polarimetric variables can be deduced from the estimates of particle characteristic size. Uncertainties of CDR-based aspect ratio retrievals are estimated at about 0.1–0.15. Given these uncertainties, radar-based retrievals generally agreed with in situ measurements. The advantages of using the CDR proxy compared to the linear depolarization ratio are discussed.

Increasing aspect ratio of particles suppresses buckling in shells formed by drying suspensions

Soft Matter ◽  
2020 ◽  
Vol 16 (42) ◽  
pp. 9643-9647
Author(s):  
Ahmed Al Harraq ◽  
Bhuvnesh Bharti
Keyword(s):  
Aspect Ratio ◽  
Particle Shape ◽  
Colloidal Suspensions ◽  
Shape Anisotropy

The article identifies the role of particle shape anisotropy in suppressing the buckling of drying droplets of colloidal suspensions.

scholarly journals Aspect-ratio-dependent interaction of molecular polymer brushes and multicellular tumour spheroids

2018 ◽  
Vol 9 (25) ◽  
pp. 3461-3465 ◽  
Author(s):  
Markus Müllner ◽  
Kylie Yang ◽  
Amandeep Kaur ◽  
Elizabeth J. New
Keyword(s):  
Aspect Ratio ◽  
Surface Chemistry ◽  
Particle Shape ◽  
Polymer Brushes ◽  
Design Parameters ◽  
Tumour Spheroid ◽  
Tumour Spheroids ◽  
Shape Effects ◽  
Nanoparticle Design ◽  
Dependent Interaction

Molecular polymer brushes allow for independent tailoring of nanoparticle design parameters. Brush particles with altered shape and aspect ratio revealed that particle shape effects may be decoupled from surface chemistry to achieve higher tumour spheroid interaction and penetration.

Measurement of Effective Viscosity in Bubbly Flow Using Free-Falling Sphere

2003 ◽  
Author(s):  
Hiroshi Oiwa ◽  
Yuichi Murai ◽  
Masa-aki Ishikawa ◽  
Fujio Yamamoto
Keyword(s):  
Effective Viscosity ◽  
Two Phase Flow ◽  
Bubbly Flow ◽  
Relative Viscosity ◽  
Stress Transfer ◽  
Phase Flow ◽  
Two Phase ◽  
Falling Sphere ◽  
Phase Medium ◽  
Free Falling

Effective viscosity of bubbly two-phase flow is experimentally investigated by means of the falling sphere method. The terminal falling velocity of the sphere is measured by image processing to calculate the relative viscosity of the two-phase flow to the single-phase flow. The measurement results show that the effective viscosity is reduced for a range from 0 to 2% of void fraction as the shearing Weber number increases. This fact implies that the reduction of the effective viscosity is governed by the deformation of the bubbles, and the mechanism is explained by the interruption of the shear stress transfer in the two-phase medium.

Equilibrium radial positions of neutrally buoyant spherical particles over the circular cross-section in Poiseuille flow

2017 ◽  
Vol 813 ◽  
pp. 750-767 ◽  
Author(s):  
Yusuke Morita ◽  
Tomoaki Itano ◽  
Masako Sugihara-Seki
Keyword(s):  
Experimental Study ◽  
Cross Section ◽  
Poiseuille Flow ◽  
Equilibrium Position ◽  
Probability Function ◽  
Circular Cross Section ◽  
Spherical Particles ◽  
Inertial Migration ◽  
Entry Length ◽  
Neutrally Buoyant

An experimental study of the inertial migration of neutrally buoyant spherical particles suspended in the Poiseuille flow through circular tubes has been conducted at Reynolds numbers $(Re)$ from 100 to 1100 for particle-to-tube diameter ratios of ${\sim}$0.1. The distributions of particles in the tube cross-section were measured at various distances from the tube inlet and the radial probability function of particles was calculated. At relatively high $Re$, the radial probability function was found to have two peaks, corresponding to the so-called Segre–Silberberg annulus and the inner annulus, the latter of which was first reported experimentally by Matas et al. (J. Fluid Mech. vol. 515, 2004, pp. 171–195) to represent accumulation of particles at smaller radial positions than the Segre–Silberberg annulus. They assumed that the inner annulus would be an equilibrium position of particles, where the resultant lateral force on the particles disappears, similar to the Segre–Silberberg annulus. The present experimental study showed that the fraction of particles observed on the Segre–Silberberg annulus increased and the fraction on the inner annulus decreased further downstream, accompanying an outward shift of the inner annulus towards the Segre–Silberberg annulus and a decrease in its width. These results suggested that if the tubes were long enough, the inner annulus would disappear such that all particles would be focused on the Segre–Silberberg annulus for $Re<1000$. At the cross-section nearest to the tube inlet, particles were absent in the peripheral region close to the tube wall including the expected Segre–Silberberg annulus position for $Re>700$. In addition, the entry length after which radial migration has fully developed was found to increase with increasing $Re$, in contrast to the conventional estimate. These results may be related to the developing flow in the tube entrance region where the radial force profile would be different from that of the fully developed Poiseuille flow and there may not be an equilibrium position corresponding to the Segre–Silberberg annulus.

Influence of Particle Shape and Contact Parameters on DEM-Simulated Bulk Density of Wheat

2020 ◽  
Vol 63 (6) ◽  
pp. 1657-1672
Author(s):  
Marvin C. Petingco ◽  
Mark E. Casada ◽  
Ronaldo G. Maghirang ◽  
Oladiran O. Fasina ◽  
Zhengpu Chen ◽  
...  
Keyword(s):  
Aspect Ratio ◽  
Bulk Density ◽  
Particle Shape ◽  
Static Friction ◽  
Rolling Friction ◽  
Particle Model ◽  
Dem Simulation ◽  
Aspect Ratios ◽  
Ellipsoidal Particles ◽  
Contact Parameters

HighlightsDecreasing aspect ratio and improved geometrical smoothness of particles increased DEM-predicted bulk density of wheat.Among the three particle models, the 5-sphere ellipsoidal particle was the best option to represent wheat particles, as indicated by the simulated bulk densities that best agreed with the experiments.Among the contact parameters, the wheat-to-wheat coefficient of static friction and wheat-surface coefficient of rolling friction had the greatest influence on simulated bulk density.Abstract. The discrete element method (DEM) has been shown to be an effective tool for simulating the behavior of granular material. The accuracy of simulations depends highly on the contact models, particle physical parameters, and contact parameters used. The objectives of this study were to determine the influence of particle shape and contact parameters on simulated wheat bulk density and to develop an effective wheat particle model for DEM simulation of filling a container using EDEM software. Grain characteristics, including single-kernel weight, kernel density, kernel dimensions, aspect ratio, and bulk density, were determined for three size fractions of wheat used in the experiments. Three categories of particle models (5-sphere pseudo-ellipsoidal, 7-sphere pseudo-ellipsoidal, and ASG-generated) with varying aspect ratios and geometrical smoothness were tested in the simulations. Results showed that DEM-simulated bulk density of wheat increased with lower aspect ratio and greater geometrical smoothness of pseudo-ellipsoidal particles (7-sphere versus 5-sphere). Increasing the number of spheres to approximately 30 for better representation of wheat kernel shape, using ASG-generated particles, did not reproduce the trend of greater simulated bulk density seen in the experiments. Among the six contact parameters, the wheat-wheat coefficient of static friction and wheat-surface coefficient of rolling friction had the most significant effect on the simulated bulk density. Among the different sets of particle models, the 5-sphere pseudo-ellipsoidal particles, having aspect ratios close to that of wheat kernels in each size fraction, were found to be the most practical and appropriate particle model for use in DEM simulation of wheat bulk density. This study contributes to better understanding of the influence of particle shape and contact parameters on DEM-simulated bulk density and provides a calibrated particle model for use in simulating container filling operations. Keywords: Bulk density, Contact parameters, DEM, Particle shape, Wheat.

scholarly journals A General Method for Estimating Bulk 2D Projections of Ice Particle Shape: Theory and Applications

2019 ◽  
Vol 76 (1) ◽  
pp. 305-332 ◽  
Author(s):  
Edwin L. Dunnavan ◽  
Zhiyuan Jiang
Keyword(s):  
Aspect Ratio ◽  
Particle Shape ◽  
Ratio Distribution ◽  
Aspect Ratios ◽  
Shape Uncertainty ◽  
Aspect Ratio Distribution ◽  
Spheroidal Geometry ◽  
Orientation Parameters ◽  
General Method

Abstract The orientation of falling ice particles directly influences estimates of microphysical and radiative bulk quantities as well as in situ retrievals of size, shape, and mass. However, retrieval efforts and bulk calculations often incorporate very basic orientations or ignore these effects altogether. To address this deficiency, this study develops a general method for projecting bulk distributions of particle shape for arbitrary orientations. The Amoroso distribution provides the most general bulk aspect ratio distribution for gamma-distributed particle axis lengths. The parameters that govern the behavior of this aspect ratio distribution depend on the assumed relationship between mass, maximum dimension, and aspect ratio. Individual spheroidal geometry allows for eccentricity quantities to linearly map onto ellipse analogs, whereas aspect ratio quantities map nonlinearly. For particles viewed from their side, this analytic distinction leads to substantially larger errors in projected aspect ratio than for projected eccentricity. Distribution transformations using these mapping equations and numerical integration of projection kernels show that both truncation of size distributions and changes in Gaussian dispersion can alter the modality and shape of projection distributions. As a result, the projection process can more than triple the relative entropy between the spheroidal and projection distributions for commonly assumed model and orientation parameters. This shape uncertainty is maximized for distributions of highly eccentric particles and for particles like aggregates that are thought to fall with large canting-angle deviations. As a result, the methods used to report projected aspect ratios and the corresponding values should be questioned.

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