scholarly journals A scaled MP-PIC method for bubbling fluidization

2021 ◽  
Author(s):  
Xing Zhao ◽  
Yong Jiang ◽  
Fei Li ◽  
Wei Wang
Keyword(s):  
Fluidized Beds ◽  
Volume Fraction ◽  
Phase Particle ◽  
Scaling Law ◽  
Coarse Graining ◽  
Coarse Grained ◽  
Particle In Cell ◽  
Wide Range ◽  
Pic Method ◽  
Multi Phase

Coarse-grained methods have been widely used in simulations of gas-solid fluidization. However, as a key parameter, the coarse-graining ratio, and its relevant scaling law is still far from reaching a consensus. In this work, a scaling law is developed based on a similarity analysis, and then it is used to scale the multi-phase particle-in-cell (MP-PIC) method, and validated in the simulation of two bubbling fluidized beds. The simulation result shows this scaled MP-PIC can reduce the errors of solids volume fraction and velocity distributions over a wide range of coarse-graining ratios. In future, we expect that a scaling law with consideration of the heterogeneity inside a parcel or numerical particle will further improve the performance of coarse-grained modeling in simulation of fluidized beds.

Development of coarse-graining DNA models for single-nucleotide resolution analysis

2010 ◽  
Vol 368 (1920) ◽  
pp. 2615-2628 ◽  
Author(s):  
Kentaro Doi ◽  
Tomoaki Haga ◽  
Hirofumi Shintaku ◽  
Satoyuki Kawano
Keyword(s):  
Dna Sequences ◽  
Persistence Length ◽  
Analytical Techniques ◽  
Coarse Graining ◽  
Coarse Grained ◽  
Nucleotide Polymorphisms ◽  
Single Nucleotide ◽  
Wide Range ◽  
Nucleotide Resolution ◽  
Single Nucleotide Resolution

Recently, analytical techniques have been developed for detecting single-nucleotide polymorphisms in DNA sequences. Improvements of the sequence identification techniques has attracted much attention in several fields. However, there are many things that have not been clarified about DNA. In the present study, we have developed a coarse-graining DNA model with single-nucleotide resolution, in which potential functions for hydrogen bonds and the π -stack effect are taken into account. Using Langevin-dynamics simulations, several characteristics of the coarse-grained DNA have been clarified. The validity of the present model has been confirmed, compared with other experimental and computational results. In particular, the melting temperature and persistence length are in good agreement with the experimental results for a wide range of salt concentrations.

Powder Metallurgy of Nanostructured High Strength Materials

2007 ◽  
Vol 534-536 ◽  
pp. 1405-1408 ◽  
Author(s):  
Jürgen Eckert ◽  
S. Scudino ◽  
P. Yu ◽  
C. Duhamel
Keyword(s):  
Powder Metallurgy ◽  
Deformation Behavior ◽  
Volume Fraction ◽  
High Strength ◽  
Mechanical Deformation ◽  
Intrinsic Properties ◽  
Mechanical Attrition ◽  
Wide Range ◽  
Multi Phase ◽  
Strength And Ductility

Nanostructured or partially amorphous Al- and Zr-based alloys are attractive candidates for advanced high-strength lightweight materials. The strength of such materials is often 2 – 3 times higher than the strength of commercial crystalline alloys. Further property improvements are achievable by designing multi-phase composite materials with optimized length scale and intrinsic properties of the constituent phases. Such alloys can be prepared by quenching from the melt or by powder metallurgy using mechanical attrition techniques. This paper focuses on mechanically attrited powders containing amorphous or nano-(quasi)crystalline phases and on their consolidation into bulk specimens. Selected examples of mechanical deformation behavior are presented, revealing that the properties can be tuned within a wide range of strength and ductility as a function of size and volume fraction of the different phases.

Multiphase Particle-in-Cell Simulations of Flow in a Gas-Solid Riser

Volume 1 ◽  
2004 ◽  
Author(s):  
K. A. Williams ◽  
D. M. Snider ◽  
J. R. Torczynski ◽  
S. M. Trujillo ◽  
T. J. O’Hern
Keyword(s):  
Gas Flow ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Three Dimensional ◽  
Extensive Study ◽  
Computational Results ◽  
Particle In Cell ◽  
Large Numbers ◽  
Wide Range ◽  
Experimental Values

The commercial computational fluid dynamics (CFD) code Arena-flow is used to simulate the transient, three-dimensional flow in a gas-solid riser at Sandia National Laboratories. Arena-flow uses a multiphase particle-in-cell (MP-PIC) numerical method. The gas flow is treated in an Eulerian manner, and the particle flow is represented in a Lagrangian manner by large numbers of discrete particle clouds with distributions of particle properties. Simulations are performed using the experimental values of the gas superficial velocity and the solids mass flux in the riser. Fluid catalytic cracking (FCC) particles are investigated. The experimental and computed pressure and solid-volume-fraction distributions are compared and found to be in reasonable agreement although the experimental results exhibit more variation along the height of the riser than the computational results do. An extensive study is performed to assess the sensitivity of the computational results to a wide range of physical and numerical parameters. The computational results are seen to be robust. Thus, the uncertainties in these parameters cannot account for the differences between the experimental and computational results.

Process Modeling: Lost-Foam Pattern Filling

2004 ◽  
Author(s):  
Peter J. Blaser ◽  
Dale M. Snider ◽  
Ken A. Williams ◽  
Alan E. Cook ◽  
Mark Hoover
Keyword(s):  
Boundary Conditions ◽  
Numerical Method ◽  
Phase Particle ◽  
Three Dimensional ◽  
Video Data ◽  
Particle In Cell ◽  
Polystyrene Beads ◽  
Multi Phase ◽  
Foam Pattern ◽  
Lost Foam

A transient, three-dimensional, multi-phase particle-in-cell approach is used to solve for the flow of polystyrene beads in complex three dimensional geometries which represent patterns used for lost-foam casting. The numerical method solves the gas conservation equations on an Eulerian grid and the motion of polystyrene beads is calculated in a Lagrangian frame of reference. The true particle size distribution is modeled, and the particle flow ranges from dilute to close-pack. Predicted fill behavior is compared to experimentally blown patterns using colored beads and to the measured transient filling of a pattern. The colored beads show a complex fill pattern which is calculated well by the numerical method. The transient calculation compares very well with measured video data, and the particle motion has unique particle behavior unlike a fluid. Because of uncertainties in boundary conditions in production lost-foam tooling, the sensitivity of lost-foam pattern filling to boundary conditions is examined.

scholarly journals Effective potential reveals evolutionary trajectories in complex fitness landscapes

2019 ◽  
Author(s):  
Matteo Smerlak
Keyword(s):  
Effective Potential ◽  
Evolutionary Dynamics ◽  
Fitness Landscape ◽  
Coarse Graining ◽  
Fitness Landscapes ◽  
Coarse Grained ◽  
Mutational Robustness ◽  
Sequencing Technologies ◽  
Wide Range ◽  
Evolutionary Trajectories

AbstractGrowing efforts to measure fitness landscapes in molecular and microbial systems are premised on a tight relationship between landscape topography and evolutionary trajectories. This relationship, however, is far from being straightforward: depending on their mutation rate, Darwinian populations can climb the closest fitness peak (survival of the fittest), settle in lower regions with higher mutational robustness (survival of the flattest), or fail to adapt altogether (error catastrophes). These bifurcations highlight that evolution does not necessarily drive populations “from lower peak to higher peak”, as Wright imagined. The problem therefore remains: how exactly does a complex landscape topography constrain evolution, and can we predict where it will go next? Here I introduce a generalization of quasispecies theory which identifies metastable evolutionary states as minima of an effective potential. From this representation I derive a coarse-grained, Markov state model of evolution, which in turn forms a basis for evolutionary predictions across a wide range of mutation rates. Because the effective potential is related to the ground state of a quantum Hamiltonian, my approach could stimulate fruitful interactions between evolutionary dynamics and quantum many-body theory.SIGNIFICANCE STATEMENTThe course of evolution is determined by the relationship between heritable types and their adaptive values, the fitness landscape. Thanks to the explosive development of sequencing technologies, fitness landscapes have now been measured in a diversity of systems from molecules to micro-organisms. How can we turn these data into evolutionary predictions? I show that preferred evolutionary trajectories are revealed when the effects of selection and mutations are blended in a single effective evolutionary force. With this reformulation, the dynamics of selection and mutation becomes Markovian, bringing a wealth of classical visualization and analysis tools to bear on evolutionary dynamics. Among these is a coarse-graining of evolutionary dynamics along its metastable states which greatly reduces the complexity of the prediction problem.

Patterns in diversity and composition of the microbenthos of subarctic intertidal beaches with different morphodynamics

2020 ◽  
Vol 648 ◽  
pp. 19-38
Author(s):  
AI Azovsky ◽  
YA Mazei ◽  
MA Saburova ◽  
PV Sapozhnikov
Keyword(s):  
Species Abundance ◽  
Abundance Ratio ◽  
Wave Action ◽  
Coarse Grained ◽  
Sediment Properties ◽  
Β Diversity ◽  
Α Diversity ◽  
Wide Range ◽  
Similar Mode ◽  
Abundance And Diversity

Diversity and composition of benthic diatom algae and ciliates were studied at several beaches along the White and Barents seas: from highly exposed, reflective beaches with coarse-grained sands to sheltered, dissipative silty-sandy flats. For diatoms, the epipelic to epipsammic species abundance ratio was significantly correlated with the beach index and mean particle size, while neither α-diversity measures nor mean cell length were related to beach properties. In contrast, most of the characteristics of ciliate assemblages (diversity, total abundance and biomass, mean individual weight and percentage of karyorelictids) demonstrated a strong correlation to beach properties, remaining low at exposed beaches but increasing sharply in more sheltered conditions. β-diversity did not correlate with beach properties for either diatoms or ciliates. We suggest that wave action and sediment properties are the main drivers controlling the diversity and composition of the intertidal microbenthos. Diatoms and ciliates, however, demonstrated divergent response to these factors. Epipelic and epipsammic diatoms exhibited 2 different strategies to adapt to their environments and therefore were complementarily distributed along the environmental gradient and compensated for each other in diversity. Most ciliates demonstrated a similar mode of habitat selection but differed in their degree of tolerance. Euryporal (including mesoporal) species were relatively tolerant to wave action and therefore occurred under a wide range of beach conditions, though their abundance and diversity were highest in fine, relatively stable sediments on sheltered beaches, whereas the specific interstitial (i.e. genuine microporal) species were mostly restricted to only these habitats.

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