scholarly journals Generalized Formula of the Fraction of Interphase for Polydisperse Non-Spherical Particles: Theoretical and Numerical Models

2019 ◽  
Vol 21 (4) ◽  
pp. 72-72
Author(s):  
Zhigang Zhu ◽  
Wenxiang Xu
Keyword(s):  
Numerical Models ◽  
Spherical Particles

scholarly journals Analytical and numerical assessment of the effect of highly conductive inclusions distribution on the thermal conductivity of particulate composites

2019 ◽  
Vol 53 (25) ◽  
pp. 3499-3514 ◽  
Author(s):  
Kamran A Khan ◽  
Falah Al Hajeri ◽  
Muhammad A Khan
Keyword(s):  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Numerical Models ◽  
Random Network ◽  
Experimental Studies ◽  
Percolation Model ◽  
Spherical Particles ◽  
Particulate Composites ◽  
Advanced Composites ◽  
Micromechanical Models

Highly conductive composites have found applications in thermal management, and the effective thermal conductivity plays a vital role in understanding the thermo-mechanical behavior of advanced composites. Experimental studies show that when highly conductive inclusions embedded in a polymeric matrix the particle forms conductive chain that drastically increase the effective thermal conductivity of two-phase particulate composites. In this study, we introduce a random network three dimensional (3D) percolation model which closely represent the experimentally observed scenario of the formation of the conductive chain by spherical particles. The prediction of the effective thermal conductivity obtained from percolation models is compared with the conventional micromechanical models of particulate composites having the cubical arrangement, the hexagonal arrangement and the random distribution of the spheres. In addition to that, the capabilities of predicting the effective thermal conductivity of a composite by different analytical models, micromechanical models, and, numerical models are also discussed and compared with the experimental data available in the literature. The results showed that random network percolation models give reasonable estimates of the effective thermal conductivity of the highly conductive particulate composites only in some cases. It is found that the developed percolation models perfectly represent the case of conduction through a composite containing randomly suspended interacting spheres and yield effective thermal conductivity results close to Jeffery's model. It is concluded that a more refined random network percolation model with the directional conductive chain of spheres should be developed to predict the effective thermal conductivity of advanced composites containing highly conductive inclusions.

scholarly journals Measuring binary fluidization of non-spherical and spherical particles using machine learning aided image processing

2021 ◽  
Author(s):  
Cheng Li ◽  
Xi Gao ◽  
Steven Rowan ◽  
Bryan Hughes ◽  
William Rogers
Keyword(s):  
Machine Learning ◽  
Particle Tracking Velocimetry ◽  
Numerical Models ◽  
Classification Model ◽  
Spherical Particles ◽  
Bed Height ◽  
Image Velocimetry ◽  
Wood Particles ◽  
Particle Velocities ◽  
Superficial Gas Velocity

The binary fluidization of Geldart-D type non-spherical wood particles and spherical LDPE particles was investigated in a laboratory-scale bed. The experiment was performed for varying static bed height, wood particles count, as well as superficial gas velocity. The LDPE velocity field were quantified using Particle Image Velocimetry (PIV). The wood particles orientation and velocity are measured using Particle Tracking Velocimetry (PTV). A machine learning pixel-wise classification model was trained and applied to acquire wood and LDPE particle masks for PIV and PTV processing, respectively. The results show significant differences in the fluidization behavior between LDPE only case and binary fluidization case. The effects of wood particles on the slugging frequency, mean, and variation of bed height, and characteristics of the particle velocities/orientations were quantified and compared. This comprehensive experimental dataset serves as a benchmark for validating numerical models.

Highly Nonlinear Solitary Waves to Estimate Orientation and Degree of Anisotropy in Rocks

2021 ◽  
Vol 79 (10) ◽  
pp. 991-1004
Author(s):  
Hoda Jalali ◽  
Yuhui Zeng ◽  
Piervincenzo Rizzo ◽  
Andrew Bunger
Keyword(s):  
Solitary Waves ◽  
Numerical Models ◽  
Spherical Particles ◽  
Highly Nonlinear ◽  
Degree Of Anisotropy ◽  
Highly Nonlinear Solitary Waves ◽  
Rock Interface ◽  
Nondestructive Identification ◽  
Nonlinear Solitary Waves

This paper delves into the use of highly nonlinear solitary waves for the nondestructive identification and characterization of anisotropy in rocks. The nondestructive testing approach proposed expands upon a technique developed recently by some of the authors for the nondestructive characterization of engineering materials and structures. The technique uses the characteristics of solitary waves propagating in a periodic array of spherical particles in contact with the rock to be characterized. The features of the waves that bounce off the chain rock interface are used to infer some properties of the geomaterial under consideration. Numerical models and experimental validation were conducted to explore the feasibility of the method and to standardize the methodology for future widespread applications.

Drying Rate of Wood Particles With Longitudinal Mass Transfer

1985 ◽  
Vol 107 (1) ◽  
pp. 12-18 ◽  
Author(s):  
B. Dorri ◽  
A. F. Emery ◽  
P. C. Malte
Keyword(s):  
Numerical Models ◽  
Spherical Particles ◽  
Drying Rate ◽  
Evaporation Front ◽  
Dimensional Model ◽  
One Dimensional ◽  
Wood Particles ◽  
Small Wood ◽  
The One ◽  
Rectangular Model

The drying of small wood particles of shape L:W:t = 3 to 5:2:1 is examined by three numerical models, and results are compared to measurements. (i) A one-dimensional rectangular model has liquid water concentrated in the center of a particle, and this is removed as an evaporation front propagates into the liquid. (ii) The one-dimensional model is also treated by the volume-averaged, or “smeared” approach, for which the moisture at any point is a distribution of liquid and vapor. For the simple rectangular geometry, the frontal and smeared models give similar results. (iii) Equivalent spherical particles are analyzed by a smeared model which includes capillarity. Reasonable agreement is obtained between the spherical results and the measurements, though an overprediction in drying rate occurs for slender particles.

Investigating fault sinuosity using discrete element modelling in 3D

2020 ◽  
Author(s):  
Janis Aleksans ◽  
Conrad Childs ◽  
Martin Schöpfer
Keyword(s):  
Numerical Models ◽  
Distinct Element ◽  
Normal Fault ◽  
Confining Pressure ◽  
Three Dimensions ◽  
Spherical Particles ◽  
Particle Flow Code ◽  
Discrete Element Modelling ◽  
Normal Faults ◽  
Fault Systems

<p>Scaled numerical models of faults are useful complements to geological data and by providing insights into fault dynamics they can improve our understanding of the different stages of development of normal fault systems, from nucleation through to localisation and maturity.</p><p>In this work, we use Particle Flow Code in three dimensions, which implements the Distinct Element Method (DEM), to study the development of systems of normal faults. The modelling is based on spherical particles that interact via a linear force-displacement law. Cohesion is modelled by adding linear elastic bonds to particle-particle contacts. These bonds break if the critical normal or shear strength is exceeded, thus creating a fracture surface within the rock volume. Model boundaries are represented by rigid and frictionless walls enclosing the modelled volume vertically and at the ends, with periodic lateral boundaries. Extension is replicated by slowly moving the end walls away from the centre while maintaining a constant confining pressure.</p><p>The DEM models replicate many aspects of the geometry and dynamics of natural fault systems with stages of fault nucleation, propagation, interaction and linkage. Here we focus on the sinuosity of model fault map traces which show a similar variability to that seen in nature. In the models, fault trace sinuosity is negatively correlated with the Young’s modulus of the rock, so that faults become less sinuous as the stiffness of the solid medium increases. This relationship supports a model in which the lengths of fault segments formed at the early stages of extension are smaller in rocks with lower Young’s modulus than in rocks with higher Young’s modulus. Longer initial fault segments become connected as displacement increases, to give lower sinuosity faults.</p>

Experimental analysis of segregation in granular flows

2020 ◽  
Author(s):  
Silvia D'Agostino
Keyword(s):  
Grain Size ◽  
Free Surface ◽  
Numerical Models ◽  
Granular Flows ◽  
Contact Forces ◽  
Spherical Particles ◽  
Granular Temperature ◽  
Bulk Solid ◽  
Large Particles ◽  
Mean Diameter

<p>Natural granular flows have a widely dispersed grain size distribution. The majority of the numerical models and laboratory investigations of granular flows are developed assuming a single grain size. However, the geophysical massive flows involve several classes of particles and the bulk solid evolves spatially in a non-uniform state [1]. Segregation causes a different spatial distribution of the particles and influences the kinematic of the bulk solid, like the concentration, the run-out, the velocity and the granular temperature. During the flow motion, the largest particles are found at the surface due to the imbalances in the contact forces, and the smallest at the bottom as they percolate due to gravity [2].</p><p>To investigate the physical processes responsible of the particles transfer, we conducted a series of laboratory experiments, using two different grain size classes to reproduce the binary mixture. The measured data are required to calibrate the mathematical model and to set the coefficients that describe the percolation and the kinetic sieving mechanism. The experiments to study the free surface flow started considering the dry condition. Two different type of classes of particles flow over a loose deposit in homogenous and steady conditions. We used spherical particles of non-expanded polystyrene with a density of 1035 kg/m<sup>3</sup>. The small beads are black with a mean diameter of 0.00075 m and the large beads are white with a mean diameter of 0.0014 m. At the end of the flume there is a weir with two openings. The material is manually inserted and flow in the flume, it is then recirculated by an auger and finally conveyed in a hopper, from where it falls down in the chute again. The system works for at least 30 minutes, after reaching the steady condition.</p><p>The measurements were taken through a high speed camera in a section lateral to the flume. The flow field was measured with an optical method, that gives the velocity, the concentration and the granular temperature for both the small and the large particles, from the sidewalls.</p><p>Analyzing the experimental data, as regards the longitudinal velocity, it is possible to observe that the velocities of the two classes are similar and the large particles flow a bit faster. In contrast, there is a strong segregation in the concentration rates. After the running time, segregation causes the separation of the two classes: the largest classes are in the upper part and the smallest fraction at the bottom.</p><p> </p><p>References</p><p>1 Drahun J.A., Bridgwater J. The mechanisms of free surface segregation, Powder Technology, 36, 39-53, 1988.</p><p>2 Savage S., Lun K.K. Particle size segregation in inclined chute of dry cohesionless granular solids, Journal of Fluid Mechanics, 189, 311-335, 1988.</p><p> </p>

STEM Study of Surface Plasmon Excitation in Small Spherical Particles

1990 ◽  
Vol 48 (2) ◽  
pp. 42-43
Author(s):  
Daniel UGARTE
Keyword(s):  
Energy Loss ◽  
Spherical Particles ◽  
Small Particles ◽  
Bulk Materials ◽  
Low Loss ◽  
Plasmon Excitation ◽  
Surface Modes ◽  
Surface Plasmon Excitation ◽  
Analytical Electron ◽  
Analytical Electron Microscope

Small particles exhibit chemical and physical behaviors substantially different from bulk materials. This is due to the fact that boundary conditions can induce specific constraints on the observed properties. As an example, energy loss experiments carried out in an analytical electron microscope, constitute a powerful technique to investigate the excitation of collective surface modes (plasmons), which are modified in a limited size medium. In this work a STEM VG HB501 has been used to study the low energy loss spectrum (1-40 eV) of silicon spherical particles [1], and the spatial localization of the different modes has been analyzed through digitally acquired energy filtered images. This material and its oxides have been extensively studied and are very well characterized, because of their applications in microelectronics. These particles are thus ideal objects to test the validity of theories developed up to now.Typical EELS spectra in the low loss region are shown in fig. 2 and energy filtered images for the main spectral features in fig. 3.

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