Large-scale simulations of Ostwald ripening in elastically stressed solids. II. Coarsening kinetics and particle size distribution

2004 ◽  
Vol 52 (5) ◽  
pp. 1365-1378 ◽  
Author(s):  
K Thornton
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Large Scale ◽  
Ostwald Ripening ◽  
Coarsening Kinetics ◽  
Large Scale Simulations

scholarly journals Effects of CO<sub>2</sub> on particle size distribution and phytoplankton abundance during a mesocosm bloom experiment (PeECE II)

2008 ◽  
Vol 5 (2) ◽  
pp. 509-521 ◽  
Author(s):  
A. Engel ◽  
K. G. Schulz ◽  
U. Riebesell ◽  
R. Bellerby ◽  
B. Delille ◽  
...  
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Large Scale ◽  
Phytoplankton Community ◽  
Co2 Enrichment ◽  
Suspended Particles ◽  
Phytoplankton Abundance ◽  
General Importance ◽  
Co2 Treatment

Abstract. The influence of seawater carbon dioxide (CO2) concentration on the size distribution of suspended particles (2–60 μm) and on phytoplankton abundance was investigated during a mesocosm experiment at the large scale facility (LFS) in Bergen, Norway, in the frame of the Pelagic Ecosystem CO2 Enrichment study (PeECE II). In nine outdoor enclosures the partial pressure of CO2 in seawater was modified by an aeration system to simulate past (~190 μatm CO2), present (~370 μatm CO2) and future (~700 μatm CO2) CO2 conditions in triplicates. Due to the initial addition of inorganic nutrients, phytoplankton blooms developed in all mesocosms and were monitored over a period of 19 days. Seawater samples were collected daily for analysing the abundance of suspended particles and phytoplankton with the Coulter Counter and with Flow Cytometry, respectively. During the bloom period, the abundance of small particles (<4 μm) significantly increased at past, and decreased at future CO2 levels. At that time, a direct relationship between the total-surface-to-total-volume ratio of suspended particles and DIC concentration was determined for all mesocosms. Significant changes with respect to the CO2 treatment were also observed in the phytoplankton community structure. While some populations such as diatoms seemed to be insensitive to the CO2 treatment, others like Micromonas spp. increased with CO2, or showed maximum abundance at present day CO2 (i.e. Emiliania huxleyi). The strongest response to CO2 was observed in the abundance of small autotrophic nano-plankton that strongly increased during the bloom in the past CO2 mesocosms. Together, changes in particle size distribution and phytoplankton community indicate a complex interplay between the ability of the cells to physiologically respond to changes in CO2 and size selection. Size of cells is of general importance for a variety of processes in marine systems such as diffusion-limited uptake of substrates, resource allocation, predator-prey interaction, and gravitational settling. The observed changes in particle size distribution are therefore discussed with respect to biogeochemical cycling and ecosystem functioning.

scholarly journals Theoretical analysis of particle size re-distribution due to Ostwald ripening in the fuel cell catalyst layer

Open Physics ◽  
2019 ◽  
Vol 17 (1) ◽  
pp. 779-789 ◽  
Author(s):  
Ambrož Kregar ◽  
Tomaž Katrašnik
Keyword(s):  
Particle Size ◽  
Fuel Cells ◽  
Fuel Cell ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Electric Potential ◽  
Ostwald Ripening ◽  
Particle Growth ◽  
Mean Particle Size ◽  
Fuel Cell Catalyst

Abstract The limited durability of hydrogen fuel cells is one of the main obstacles in their wider adoption as a clean alternative technology for small scale electricity production. The Ostwald ripening of catalyst material is recognized as one of the main unavoidable degradation processes deteriorating the fuel cell performance and shortening its lifetime. The paper systematically studies how the modeling approach towards the electrochemically driven Ostwald ripening in the fuel cell catalyst differs from the classical diffusion driven models and highlights how these differences affect the resulting evolution of particle size distribution. At moderately low electric potential, root-law growth of mean particle size is observed with linear relation between mean particle size and standard deviation of particle size distribution, similar to Lifshitz-Slyozov-Wagner theory, but with broader and less skewed distribution. In case of high electric potential, rapid particle growth regime is observed and qualitatively described by redeposition of platinum from a highly oversaturated solution, revealing the deficiencies of the existing platinum degradation models at describing the Ostwald ripening in the fuel cells at high electric potentials. Several improvements to the established models of platinum degradation in fuel cell catalysts are proposed, aimed at better description of the diffusion processes involved in particle growth due to Ostwald ripening.

scholarly journals From nucleation and coarsening to coalescence in metastable liquids

2020 ◽  
Vol 378 (2171) ◽  
pp. 20190247 ◽  
Author(s):  
Dmitri V. Alexandrov ◽  
Irina V. Alexandrova
Keyword(s):  
Mass Transfer ◽  
Particle Size ◽  
Distribution Function ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Ostwald Ripening ◽  
Intermediate Stage ◽  
Size Distribution Function ◽  
The Right ◽  
Transfer Mechanisms

The transition of a metastable liquid (supersaturated solution or supercooled melt) occurring from the intermediate stage (where the crystals nucleate and grow) to the concluding stage (where the larger particles evolve at the expense of the dissolution of smaller particles) is theoretically described, with allowance for various mass transfer mechanisms (reaction on the interface surface, volume diffusion, grain-boundary diffusion, diffusion along the dislocations) arising at the stage of Ostwald ripening (coalescence). The initial distribution function (its ‘tail’) for the concluding stage (forming as a result of the evolution of a particulate assemblage during the intermediate stage) is taken into account to determine the particle-size distribution function at the stage of Ostwald ripening. This modified distribution function essentially differs from the universal Lifshitz–Slyozov (LS) solutions for several mass transfer mechanisms. Namely, its maximum lies below and is shifted to the left in comparison with the LS asymptotic distribution function. In addition, the right branch of the particle-size distribution lies above and is shifted to the right of the LS blocking point. It is shown that the initial ‘tail’ of the particle-size distribution function completely determines its behaviour at the concluding stage of Ostwald ripening. The present theory agrees well with experimental data. This article is part of the theme issue ‘Patterns in soft and biological matters’.

Particle size distribution in wort during large scale brewhouse operations

AIChE Journal ◽  
2007 ◽  
Vol 53 (5) ◽  
pp. 1373-1388 ◽  
Author(s):  
F. Kühbeck ◽  
W. Back ◽  
M. Krottenthaler ◽  
T. Kurz
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Large Scale

scholarly journals Predicting continuous form of soil-water characteristics curve from limited particle size distribution data

Water SA ◽  
2018 ◽  
Vol 44 (3 July) ◽  
Author(s):  
Samaneh Amanabadi ◽  
Mohammad Hossien Mohammadi ◽  
Mohammad Hassan Masihabadi ◽  
Mehran Vazirinia
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Solute Transport ◽  
Size Distribution ◽  
Large Scale ◽  
Prediction Models ◽  
Distribution Data ◽  
Continuous Form ◽  
Water Characteristics ◽  
Transport Management

Detailed information derived from a soil moisture characteristics curve (SMC) helps in water flow and solute transport management. Hence, prediction of the SMC from soil particle size distribution (PSD), which is easy to measure, would be convenient. In this study, we combine an integrated robust PSD-based model and a Van Genuchten SMC model to predict a continuous form of SMC using sand, silt and clay percentages for 50 soils selected from the UNSODA database. We compare the performance of the proposed approach with some previous prediction models. The results indicated that the SMC can be predicted and modelled properly by using sand, silt, clay and bulk density data. The model’s bias was attributed to the high fine particle and organic carbon (OC) content. We concluded that independence of the proposed method from the database and any empirical coefficients make predictions more reliable and applicable for large-scale water and solute transport management.

scholarly journals Influence of Particle Size Distribution on the Critical State of Rockfill

2019 ◽  
Vol 2019 ◽  
pp. 1-7 ◽  
Author(s):  
Gui Yang ◽  
Yang Jiang ◽  
Sanjay Nimbalkar ◽  
Yifei Sun ◽  
Nenghui Li
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Critical State ◽  
Large Scale ◽  
Triaxial Tests ◽  
Power Law Function ◽  
Maximum Particle ◽  
Effect Of Particle Size ◽  
The Relationship

In order to study the effect of particle size distribution on the critical state of rockfill, a series of large-scale triaxial tests on rockfill with different maximum particle sizes were performed. It was observed that the intercept and gradient of the critical state line in the e−p′ plane decreased as the grading broadened with the increase in particle size while the gradient of the critical state line in the p′−q plane increased as the particle size increased. A power law function is found to appropriately describe the relationship between the critical state parameters and maximum particle size of rockfill.

Circulating Fluidized Beds

2010 ◽  
pp. 316-358
Author(s):  
Ray Cocco ◽  
S.B. Reddy Karri ◽  
Ted Knowlton
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Large Scale ◽  
Cfd Modeling ◽  
Circulating Fluidized Beds ◽  
Cfd Models ◽  
Unit Operations ◽  
Computational Fluid Dynamics Cfd

In the last 20 years, significant improvements in the computational fluid dynamics (CFD) modeling have been made that allow the simulation of large-scale, commercial CFBs. Today, commercial codes are available that can model some of this behavior in large-scale, commercial units in a reasonable amount of time. However, the hydrodynamics in a riser or fluidized bed are complex with both micro and macroscale features. From particle clustering to large streamers to the core-annulus profile, the particle behavior in these unit operations rarely behaves as a “continuous fluid.” Even the role of particle size distribution is often neglected and models that do consider particle size distribution don’t always consider the role of particle size on granular temperature. Many models use insufficient boundary conditions by assuming uniform or symmetric profiles, which is rarely the case. Furthermore, grid sizing is usually based on computer limitations instead of model limitations, and many models of commercial systems extend beyond the capability of the constitutive equations being used. Successful application of today’s CFD models requires a good understanding of the equations behind the code, the assumptions used for those equations and the capability or limitations of the code. CFD is nothing more than a guess without an understanding of the fundamentals, underlying assumptions and code limitations that are part of every model.

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