scholarly journals Computational analysis of transport in three-dimensional heterogeneous materials

2020 ◽  
Vol 23 (1-4) ◽  
Author(s):  
Gianluca Boccardo ◽  
Eleonora Crevacore ◽  
Alberto Passalacqua ◽  
Matteo Icardi
Keyword(s):  
Three Dimensional ◽  
Heterogeneous Materials ◽  
Integrated Approach ◽  
Transport Equations ◽  
Diffusion Reaction ◽  
Simple Closure ◽  
Subsurface Structures ◽  
Biological Matter ◽  
Transfer Problems ◽  
Random Packings

AbstractPorous and heterogeneous materials are found in many applications from composites, membranes, chemical reactors, and other engineered materials to biological matter and natural subsurface structures. In this work we propose an integrated approach to generate, study and upscale transport equations in random and periodic porous structures. The geometry generation is based on random algorithms or ballistic deposition. In particular, a new algorithm is proposed to generate random packings of ellipsoids with random orientation and tunable porosity and connectivity. The porous structure is then meshed using locally refined Cartesian-based or unstructured strategies. Transport equations are thus solved in a finite-volume formulation with quasi-periodic boundary conditions to simplify the upscaling problem by solving simple closure problems consistent with the classical theory of homogenisation for linear advection–diffusion–reaction operators. Existing simulation codes are extended with novel developments and integrated to produce a fully open-source simulation pipeline. A showcase of a few interesting three-dimensional applications of these computational approaches is then presented. Firstly, convergence properties and the transport and dispersion properties of a periodic arrangement of spheres are studied. Then, heat transfer problems are considered in a pipe with layers of deposited particles of different heights, and in heterogeneous anisotropic materials.

Constructive Distributed Work: An Integrated Approach to Sustainable Collaboration and Research for Distributed Teams

2021 ◽  
pp. 105065192110214
Author(s):  
Michelle McMullin ◽  
Bradley Dilger
Keyword(s):  
Best Practices ◽  
Team Building ◽  
Three Dimensional ◽  
Integrated Approach ◽  
Interdisciplinary Teams ◽  
Digital Tools ◽  
Distributed Teams ◽  
Distributed Work ◽  
Team Members ◽  
Negative Impacts

Academic work increasingly involves creating digital tools with interdisciplinary teams distributed across institutions and roles. The negative impacts of distributed work are described at length in technical communication scholarship, but such impacts have not yet been realized in collaborative practices. By integrating attention to their core ethical principles, best practices, and work patterns, the authors are developing an ethical, sustainable approach to team building that they call constructive distributed work. This article describes their integrated approach, documents the best practices that guide their research team, and models the three-dimensional thinking that helps them develop sustainable digital tools and ensure the consistent professional development of all team members.

The Use of Subgrid Transport Equations in a Three-Dimensional Model of Atmospheric Turbulence

1973 ◽  
Vol 95 (3) ◽  
pp. 429-438 ◽  
Author(s):  
J. W. Deardorff
Keyword(s):  
Boundary Layer ◽  
Three Dimensional ◽  
Transport Equations ◽  
Subgrid Scale ◽  
Reynolds Stresses ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Truncation Errors ◽  
Subgrid Scales ◽  
Grid Points

A three-dimensional numerical model of turbulence in an atmospheric boundary layer has been revised to utilize subgrid transport equations for the subgrid Reynolds stresses and fluxes rather than subgrid eddy coefficients. It was applied to a daytime boundary layer over heated ground in a region of horizontal area 8km square and 2km deep, utilizing 40×40×40 grid points. The constraints involved in selecting four important subgrid closure constants are discussed in some detail, along with maintenance of realizability on the subgrid scale. The results indicate that the subgrid transport equations produce subgrid Reynolds stresses and fluxes which realistically simulate the transfer of larger scale variance to subgrid scales, provided truncation errors due to advective terms are not too large. They also show the superiority of this method over the use of (nonstability dependent) nonlinear eddy coefficients in maintaining the sharpness of the inversion base which lies above the mixed layer.

Tu1963 Contrast Enhancement for Three-Dimensional Optical Coherence Tomography Images for Improved Delineation of Subsurface Structures

2013 ◽  
Vol 144 (5) ◽  
pp. S-892
Author(s):  
Osman O. Ahsen ◽  
Michael G. Giacomelli ◽  
Tsung-Han Tsai ◽  
Yuankai K. Tao ◽  
Hsiang-Chieh Lee ◽  
...  
Keyword(s):  
Optical Coherence Tomography ◽  
Contrast Enhancement ◽  
Three Dimensional ◽  
Optical Coherence ◽  
Subsurface Structures

scholarly journals Numerical Simulation of the Coagulation Dynamics of Blood

2008 ◽  
Vol 9 (2) ◽  
pp. 83-104 ◽  
Author(s):  
T. Bodnár ◽  
A. Sequeira
Keyword(s):  
Blood Coagulation ◽  
Computational Study ◽  
Time Integration ◽  
Three Dimensional ◽  
Circular Cross Section ◽  
Clot Formation ◽  
Diffusion Reaction ◽  
Numerical Code ◽  
Injured Region ◽  
Reaction Equations

The process of platelet activation and blood coagulation is quite complex and not yet completely understood. Recently, a phenomenological meaningful model of blood coagulation and clot formation in flowing blood that extends existing models to integrate biochemical, physiological and rheological factors, has been developed. The aim of this paper is to present results from a computational study of a simplified version of this coupled fluid-biochemistry model. A generalized Newtonian model with shear-thinning viscosity has been adopted to describe the flow of blood. To simulate the biochemical changes and transport of various enzymes, proteins and platelets involved in the coagulation process, a set of coupled advection–diffusion–reaction equations is used. Three-dimensional numerical simulations are carried out for the whole model in a straight vessel with circular cross-section, using a finite volume semi-discretization in space, on structured grids, and a multistage scheme for time integration. Clot formation and growth are investigated in the vicinity of an injured region of the vessel wall. These are preliminary results aimed at showing the validation of the model and of the numerical code.

scholarly journals Water Use Conflict and Coordination between Agricultural and Wetlands—A Case Study of Yanqi Basin

Water ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 3225
Author(s):  
Mengyao Jiang ◽  
Shuntao Xie ◽  
Shuixian Wang
Keyword(s):  
Water Use ◽  
Groundwater Level ◽  
Assessment Tool ◽  
Scientific Evidence ◽  
Three Dimensional ◽  
Correlation Coefficients ◽  
Integrated Approach ◽  
Groundwater Exploitation ◽  
Lake Recovery ◽  
Yanqi Basin

Increased groundwater extraction leads to the decrease of the extent of wetlands due to the implementation of a water-saving transformation project in an arid irrigation area. The application of integrated mitigation tools and strategies in China have increasing significance. In this study, an integrated approach (SWAT-MODFLOW) was followed; it is based on a soil and water assessment tool (SWAT) coupled with a modular three-dimensional finite difference groundwater model (MODFLOW). Recharge and evaporation values were estimated by SWAT and were then used to simulate groundwater in a MODFLOW model. Calibration (over the years 2000–2010) and validation (over the years 2010–2016) were performed, based on observed groundwater-level data; results showed that the combined SWAT-MODFLOW provides more accurate simulation and prediction of the dynamic changes of surface water and groundwater in irrigation areas than results from individual MODFLOW models. This method was applied to the Yanqi Basin, which is one of the most appropriate arid agricultural basins for modeling lake wetland and groundwater in China. The correlation coefficients (R2) between the simulated and real groundwater level are 0.96 and 0.91 in SWAT-MODFLOW and MODFLOW, respectively. With the gradual increase in the extraction to 248%, 0.62 × 108 m3 of groundwater discharged into the lake became −2.25 × 108 m3. The lake level drops 1.3 m compared with the current year, when the groundwater exploitation increases by 10 × 108 m3/year. Overall, the results of the coupling model offer scientific evidence for agricultural water management and lake recovery, so as to enhance the water use coordination.

scholarly journals Three-dimensional cellular automaton model for the destruction of brittle heterogeneous materials

2019 ◽  
Vol 129 ◽  
pp. 01020
Author(s):  
Galina Kazunina ◽  
Allay Cherednichenko
Keyword(s):  
Cellular Automaton ◽  
Correlation Functions ◽  
Damage Accumulation ◽  
Three Dimensional ◽  
Heterogeneous Materials ◽  
Electromagnetic Emission ◽  
Physical Experiments ◽  
Damage Structure ◽  
Pulsed Electromagnetic

The article investigates the evolution modes of cluster damage structure in brittle heterogeneous materials by using a three-dimensional probabilistic cellular automaton. By comparing the data of computer and physical experiments, there was established the essential role of the model parameter, which describes the intensity of the material destruction process under the influence of local overstress near the existing damage clusters - the probability of perimeter germination. The comparison of kinetic curves of damage accumulation and correlation functions showed that, depending on the probability value for damage cluster perimeter germination, two qualitatively different modes of evolution of damage accumulation process are observed. In this case, the best correspondence of correlation functions in model and physical experiment on pulsed electromagnetic emission is observed for perimeter germination probability values smaller than 0.2.

Secondary Fluorescence of 3D Heterogeneous Materials Using a Hybrid Model

2020 ◽  
Vol 26 (3) ◽  
pp. 484-496
Author(s):  
Yu Yuan ◽  
Hendrix Demers ◽  
Xianglong Wang ◽  
Raynald Gauvin
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Analytical Model ◽  
Hybrid Model ◽  
Three Dimensional ◽  
Heterogeneous Materials ◽  
X Ray ◽  
The Monte Carlo Method ◽  
Secondary Fluorescence ◽  
Good Agreement

AbstractIn electron probe microanalysis or scanning electron microscopy, the Monte Carlo method is widely used for modeling electron transport within specimens and calculating X-ray spectra. For an accurate simulation, the calculation of secondary fluorescence (SF) is necessary, especially for samples with complex geometries. In this study, we developed a program, using a hybrid model that combines the Monte Carlo simulation with an analytical model, to perform SF correction for three-dimensional (3D) heterogeneous materials. The Monte Carlo simulation is performed using MC X-ray, a Monte Carlo program, to obtain the 3D primary X-ray distribution, which becomes the input of the analytical model. The voxel-based calculation of MC X-ray enables the model to be applicable to arbitrary samples. We demonstrate the derivation of the analytical model in detail and present the 3D X-ray distributions for both primary and secondary fluorescence to illustrate the capability of our program. Examples for non-diffusion couples and spherical inclusions inside matrices are shown. The results of our program are compared with experimental data from references and with results from other Monte Carlo codes. They are found to be in good agreement.

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