scholarly journals Migration Simulation of Radioactive Soil Particles in the Atmospheric Environment Using CFD-DEM Coupled with Empirical Formulas

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Liwei Chen ◽  
Chunhua Chen ◽  
Qingchun Fan ◽  
Zihui Yang ◽  
Zihao Zheng ◽  
...  
Keyword(s):  
Empirical Model ◽  
Coupled Model ◽  
Secondary Emission ◽  
Particle Migration ◽  
Radioactive Material ◽  
Atmospheric Environment ◽  
Empirical Formulas ◽  
Radioactive Particle ◽  
Distribution Features ◽  
And Migration

Radioactive particle migration from the soil surface is an unignorable factor for the radioactive material distribution prediction after a nuclear accident, especially for the decision support of radioactive disposal. Considering the continuous emission, collision, and reattachment of radioactive particles, a creative simulation method with a coupled model was proposed, which combines an empirical model and the CFD-DEM method, and was established to simulate the secondary emission and motion of radioactive particles. The source term of the radioactive particles is estimated by an empirical model as the input of the CFD-DEM. Regarding the characteristics of the particle motion, the spout-fluidized bed simulation by the coupled model is consistent with the referred simulation results and experimental data, which validates the correctness of this model. The coupling model was applied to simulate the radioactive particle distribution and migration on the nonconfined backward facing step (NBFS). The simulation reveals that the distribution features and migration flux of the radioactive particles can be estimated in detail by the proposed model, which can help to provide more actual information for radioactive disposal after nuclear accidents.

The analysis of self-diffusion and migration of rough spheres in nonlinear shear flow using a traction-corrected boundary element method

2008 ◽  
Vol 598 ◽  
pp. 267-292 ◽  
Author(s):  
MARC S. INGBER ◽  
SHIHAI FENG ◽  
ALAN L. GRAHAM ◽  
HOWARD BRENNER
Keyword(s):  
Boundary Element Method ◽  
Shear Flow ◽  
Boundary Element ◽  
Particle Migration ◽  
Self Diffusion ◽  
Centre Of Gravity ◽  
Particle Pairs ◽  
And Migration ◽  
Nonlinear Shear ◽  
Element Method

The phenomena of self-diffusion and migration of rough spheres in nonlinear shear flows are investigated using a new traction-corrected boundary element method (TC-BEM) in which the near-field asymptotics for the traction solution in the interstitial region between two nearly touching spheres is seamlessly coupled with a traditional direct boundary element method. The TC-BEM is extremely accurate in predicting particle trajectories, and hence can be used to calculate both the particle self-diffusivity and a newly defined migration diffusivity for dilute suspensions. The migration diffusivity is a function of a nonlinearity parameter characterizing the shear flow and arises from the net displacement of the centre of gravity of particle pairs. This net displacement of the centre of gravity of particle pairs does not occur for smooth particles, nor for rough particles in a linear shear flow. An explanation is provided for why two-particle interactions of rough spheres in a nonlinear shear flow result in particle migration.

Time dependent backward piping erosion 2D modeling with laminar flow transport equations

2020 ◽  
Author(s):  
Juan Pablo Aguilar-Lopez ◽  
Manuel Wewer ◽  
Thom Bogaard ◽  
Matthijs Kok
Keyword(s):  
Sediment Transport ◽  
Coupled Model ◽  
Mass Conservation ◽  
Element Model ◽  
Great Accuracy ◽  
Conservation Equation ◽  
Empirical Formulas ◽  
Important Conclusion ◽  
Scale Experiment ◽  
Piping Erosion

<p>Backward piping erosion (BEP) is a highly complex erosive process which occurs on granular soils when large head differences are exerted. This process represents a significant threat to dams and levees stability and therefore a large part of the design and reliability assessment of these water retaining structures is devoted to this single process. Several authors have achieved great accuracy in predicting the critical head difference that triggers the process but not so much has been studied regarding the time of occurrence and the duration of the erosive process.  In the present study we propose a 2D finite element model for which not only the critical head difference can be predicted but also the development of the erosive process in time. This was achieved by coupling the 2D Darcy partial differential equation with Exner’s 1D sediment transport mass conservation equation. Different laminar sediment transport rate empirical models were tested and used as inputs in the coupled model. To test the performance of the proposed model, the IJkdijk real scale experiment for piping erosion was simulated. The results show that the model is capable of predicting not only the critical head and its progression in time but also specific events of the process such as the instants of start of the erosion and the  complete seepage length development . An important conclusion of the study is that from several transport empirical formulas tested, the model from Yalin which is widely recognized by the sediment transport community performs the best.</p>

scholarly journals An Analysis of Mexican Remigration To The U.S.

1970 ◽  
Vol 26 (1) ◽  
pp. 55-72
Author(s):  
David Molina ◽  
R. Todd Jewell
Keyword(s):  
Empirical Model ◽  
Temporary Workers ◽  
Undocumented Migrants ◽  
Mexican Migrants ◽  
Illegal Migrants ◽  
Migration Networks ◽  
Market Factors ◽  
Using Data ◽  
And Migration ◽  
The U.S

This paper presents an analysis of Mexican migrants to the U.S. and theirdecisions to remigrate. We concentrate on the relative impacts of market and nonmarketfactors such as income, remittances, and migration networks. We analyze theremigration decision of male, illegal migrants using data from the Mexican MigrationProject. Current migration proposals are geared towards policy that would allowfor some type of temporary workers. The empirical model presented here allowsfor a comparison of the relative impacts of market and non-market factors on thedecision to choose among different remigration options. The results indicate thatincome, remittances, and migration networks have significant effects on the remigrationdecisions of male, undocumented migrants.

scholarly journals Bias-corrected CMIP6 global dataset for dynamical downscaling of the historical and future climate (1979–2100)

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Zhongfeng Xu ◽  
Ying Han ◽  
Chi-Yung Tam ◽  
Zong-Liang Yang ◽  
Congbin Fu
Keyword(s):  
Large Scale ◽  
Dynamical Downscaling ◽  
Linear Trend ◽  
Coupled Model ◽  
Future Climate ◽  
Atmospheric Environment ◽  
Important Approach ◽  
Corrected Data ◽  
Mean Climate ◽  
The Individual

AbstractDynamical downscaling is an important approach to obtaining fine-scale weather and climate information. However, dynamical downscaling simulations are often degraded by biases in the large-scale forcing itself. We constructed a bias-corrected global dataset based on 18 models from the Coupled Model Intercomparison Project Phase 6 (CMIP6) and the European Centre for Medium-Range Weather Forecasts Reanalysis 5 (ERA5) dataset. The bias-corrected data have an ERA5-based mean climate and interannual variance, but with a non-linear trend from the ensemble mean of the 18 CMIP6 models. The dataset spans the historical time period 1979–2014 and future scenarios (SSP245 and SSP585) for 2015–2100 with a horizontal grid spacing of (1.25° × 1.25°) at six-hourly intervals. Our evaluation suggests that the bias-corrected data are of better quality than the individual CMIP6 models in terms of the climatological mean, interannual variance and extreme events. This dataset will be useful for dynamical downscaling projections of the Earth’s future climate, atmospheric environment, hydrology, agriculture, wind power, etc.

scholarly journals EFFECT OF TRANSLATE SPEED OF TYPHOONS ON WIND WAVES

2020 ◽  
pp. 14
Author(s):  
Naoto Inagaki ◽  
Tomoya Shibayama ◽  
Miguel Esteban ◽  
Tomoyuki Takabatake
Keyword(s):  
Tropical Cyclones ◽  
Empirical Model ◽  
Wind Field ◽  
Meteorological Data ◽  
Wind Waves ◽  
Coupled Model ◽  
Wind Generation ◽  
Translation Speed ◽  
Different Types ◽  
Quantitative Assessments

Quantitative assessments of the effect that changes in the translate speed of typhoons have on wind waves were carried out. A WRF-SWAN coupled model that used observed meteorological data was applied to eight different typhoons in the vicinity of Shiono-Misaki, Japan. The authors proposed a new methodology to modify the translate speed and wind field of tropical cyclones, using an empirical model in which the gross wind field is expressed as the summation of two different types of wind generation (due to either the pressure gradient or translation speed). As a result, it is important to raise awareness of the future problems that can be caused by large storms that stall for prolonged periods of time.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/oCSbyaYoNEc

Shifts in Herring and Mackerel Resources in the Northeast Atlantic under Global Warming

2021 ◽  
Author(s):  
Yuanzhuo Zeng
Keyword(s):  
Global Warming ◽  
Seawater Temperature ◽  
Coupled Model ◽  
Marine Species ◽  
Fish Populations ◽  
Fishing Industry ◽  
Migration Behavior ◽  
Northeast Atlantic ◽  
Fishing Vessels ◽  
And Migration

<p>Global warming is one of the most imminent challenges facing humanity in the 21<sup>st</sup> century. It will not only have a profound effect on ecosystems but also on economies around the world. The shift in habitats of economically important marine species caused by rising seawater temperatures will bring challenges to the existing fishing industry, especially small fishing businesses. This research tries to build mathematical models to find out shifts in herring and mackerel resources in the Northeast Atlantic under global warming, and offer advice on how to deal with potential development challenges.</p><p>First, several models are designed to predict the change in seawater temperature over the next 50 years. We base our prediction model on the Coupled Model Intercomparison Project Phase 6 (CMIP6) and conduct a detailed analysis of different possible levels of seawater temperature increases caused by different carbon emissions levels. Then the lifecycles and migration behavior of herring and mackerel are researched and the influence of seawater temperature increases on their ecosystems is predicted and charted. The tendency of herring and mackerel populations going further offshore and northerly is obvious.</p><p>Second, after analyzing the migration of fish populations, we research the fishing industry in the region and deem it necessary for small fishing companies to make adjustments to their fishing methods. If global warming follows the relatively moderate economic development model, which is the most likely scenario, fish populations will too far away for small fishing companies to harvest near 2091. Our suggested strategy is that fishing vessels capable of operating without land-based support should be increased so that they can operate in waters further from the coast to maintain the harvest.</p><p>Finally, the models’ sensitivity is tested, and the results demonstrate the effectiveness and robustness of our modeling. This research provides insights into how small fishing companies should relocate themselves to optimize their business, in order to deal with long-term development challenges, and seize the opportunity in fishing under the effects of Global Warming.</p>

Experiment-based validation and uncertainty quantification of coupled multi-scale plasticity models

2016 ◽  
Vol 12 (1) ◽  
pp. 151-176 ◽  
Author(s):  
Garrison Stevens ◽  
Sez Atamturktur ◽  
Ricardo Lebensohn ◽  
George Kaschner
Keyword(s):  
Coupled Model ◽  
Material Behavior ◽  
Radioactive Material ◽  
Material Structure ◽  
Coupled Models ◽  
Content Type ◽  
Strongly Coupled ◽  
Multi Scale ◽  
Macro Scale ◽  
Meso Scale

Purpose – Highly anisotropic zirconium is a material used in the cladding of nuclear fuel rods, ensuring containment of the radioactive material within. The complex material structure of anisotropic zirconium requires model developers to replicate not only the macro-scale stresses but also the meso-scale material behavior as the crystal structure evolves; leading to strongly coupled multi-scale plasticity models. Such strongly coupled models can be achieved through partitioned analysis techniques, which couple independently developed constituent models through an iterative exchange of inputs and outputs. Throughout this iterative process, biases, and uncertainties inherent within constituent model predictions are inevitably transferred between constituents either compensating for each other or accumulating during iterations. The paper aims to discuss these issues. Design/methodology/approach – A finite element model at the macro-scale is coupled in an iterative manner with a meso-scale viscoplastic self-consistent model, where the former supplies the stress input and latter represents the changing material properties. The authors present a systematic framework for experiment-based validation taking advantage of both separate-effect experiments conducted within each constituent’s domain to calibrate the constituents in their respective scales and integral-effect experiments executed within the coupled domain to test the validity of the coupled system. Findings – This framework developed is shown to improve predictive capability of a multi-scale plasticity model of highly anisotropic zirconium. Originality/value – For multi-scale models to be implemented to support high-consequence decisions, such as the containment of radioactive material, this transfer of biases and uncertainties must be evaluated to ensure accuracy of the predictions of the coupled model. This framework takes advantage of the transparency of partitioned analysis to reduce the accumulation of errors and uncertainties.

scholarly journals Sea level driven marsh expansion in a coupled model of marsh erosion and migration

2016 ◽  
Vol 43 (9) ◽  
pp. 4366-4373 ◽  
Author(s):  
Matthew L. Kirwan ◽  
David C. Walters ◽  
William G. Reay ◽  
Joel A. Carr
Keyword(s):  
Sea Level ◽  
Coupled Model ◽  
Marsh Erosion ◽  
And Migration

Study on Factors Influencing the Diffusion and Migration of Radionuclide Offshore in Nuclear Power Plant Accidents

2018 ◽  
Author(s):  
Li Zichao ◽  
Zhou Tao ◽  
Qin Xuemeng ◽  
Amir Haider ◽  
Li Bing ◽  
...  
Keyword(s):  
Turbulent Diffusion ◽  
Nuclear Power ◽  
Coupled Model ◽  
Radionuclide Concentration ◽  
Short Term ◽  
Power Stations ◽  
Migration Mechanism ◽  
Emergency Decision Making ◽  
And Migration ◽  
Emergency Decision

Studying the diffusion and migration mechanism of radionuclide in an offshore environment under accidental conditions of nuclear power stations is of great significance to emergency decision-making and nuclear accident mitigation. The migration mechanism of radionuclide in the ocean was studied. For the short-term situation, a multi-factor coupled model was established and the effects of turbulent diffusion, decay and adsorption sedimentation on the radionuclide concentration were analyzed. The results show that the radionuclide concentration decreases with turbulent diffusion. In the short-term, the decay of radionuclide has no effect on the concentration of 137Cs, but has a significant effect on the concentration of 131I. The maximum adsorption sedimentation rate of suspended matter to radionuclide is about 1%, which can be neglected in the short-term simulation and needs to be considered in the long-term simulation. The model can better simulate the variation of radionuclide concentration.

Sign in / Sign up

Export Citation Format

Share Document