scholarly journals A new seasonal frozen soil water-thermal coupled migration model and its numerical simulation

PLoS ONE ◽  
2021 ◽  
Vol 16 (11) ◽  
pp. e0258861
Author(s):  
Chaoyi Zhang ◽  
Feng Chen ◽  
Lei Sun ◽  
Zhangchao Ma ◽  
Yan Yao
Keyword(s):  
Numerical Simulation ◽  
Soil Temperature ◽  
Transport Model ◽  
Unit Cell ◽  
Frozen Soil ◽  
Average Error ◽  
Maximum Relative Error ◽  
Coupled Transport ◽  
Freeze Thaw ◽  
The One

In this paper, a mathematical model based on spherical differential unit cell is proposed as a model for studying seasonal freeze-thaw soil space infinitesimal differential unit cell. From this model, the basic equations of permafrost moisture and heat flow motion are directly derived, then the linked equations form the permafrost water-heat coupled transport model. On this basis, the one-dimensional seasonal permafrost water-heat transport equation is derived. The model reduces the original spatial three-variable coordinate system (parallel hexahedron) into a coupled equation with a single spherical radius (R) as the independent variable, so the iterations of the numerical simulation algorithm is greatly reduced and the complexity is decreased. Finally, the model is used to simulate the seasonal freeze-thaw soil in the ShiHeZi region of Xinjiang, China. The principle of the simulation is to collect the soil temperature and humidity values of the region in layers and fixed-points using a homemade freeze-thaw soil sensor, after that we solve it by numerical calculation using MATLAB. The analysis results show that the maximum relative error of the model we proposed is 4.36, the minimum error is 0.98, and the average error is 2.515. The numerical simulation results are basically consistent with the measured data, then the proposed model is consistent with the matching states of permafrost moisture content and soil temperature in the region at different times. In addition, the experiments also demonstrate the reliability and accuracy of the model.

Numerical simulation of coupled liquid water, stress and heat for frozen soil in the thawing process

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Wei Xiao ◽  
Enlong Liu ◽  
Xiao Yin ◽  
Guike Zhang ◽  
Chong Zhang ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Water Content ◽  
Coupled Model ◽  
Frozen Soil ◽  
Water Migration ◽  
Overburden Pressure ◽  
Content Type ◽  
Thawing Process ◽  
Sample Water ◽  
The One

PurposeThe purpose of this paper is to perform the thermo-hydro-mechanical (THM) numerical analysis in order to study the thawing process for frozen soil and to predict the thawing settlement.Design/methodology/approachA new one-dimensional multi-field physical coupled model was proposed here to describe the thawing process of saturated frozen soil, whereby the void ratio varied linearly with effective stress (Eq. 10) and hydraulic conductivity (Eq. 27b). The thawing process was simulated with different initial and boundary conditions in an open system with temperature variations. The mechanical behavior and water migration of the representative cases were also investigated.FindingsThe comparisons of representative cases with experimental data demonstrated that the model predicts thawing settlement well. It was found that the larger temperature gradient, higher overburden pressure and higher water content could lead to larger thawing settlement. The temperature was observed that to distribute height linearly in both frozen zone and unfrozen zone of the sample. Water migration forced to a decrease in the water content of the unfrozen zone and an increase in water content at the thawing front.Research limitations/implicationsIn this study, only the one-directional thawing processes along the frozen soil samples were investigated numerically and compared with test results, which can be extended to two-dimensional analysis of thawing process in frozen soil.Originality/valueThis study helps to understand the thawing process of frozen soil by coupled thermo-hydro-mechanical numerical simulation.

scholarly journals Experimental Analysis and Simulation of Novel Technical Textile Reinforced Composite of Banana Fibre

Materials ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1134 ◽  
Author(s):  
Mario Monzón ◽  
Rubén Paz ◽  
Martí Verdaguer ◽  
Luis Suárez ◽  
Pere Badalló ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Predictive Modelling ◽  
Experimental Results ◽  
Average Error ◽  
Acceptable Error ◽  
Simulation Based ◽  
Banana Fibre ◽  
The One ◽  
Textile Reinforced Composite ◽  
Definition Of

The use of natural fibres allows reducing environmental impact, due to their natural renewable origin and the lower energy needed for their production and processing. This work presents the mechanical characterization of a newly developed technical textile, with banana fibre treated by enzymes, comparing experimental results with numerical simulation based on the definition of the unit cell at micromechanical level. The experimental test shows that the composite with the fabric of banana fibre presents worse mechanical behaviour than the one with commercial flax fibre. The presence of wool, necessary for producing the yarn, reduces the mechanical properties of the banana textile. The numerical simulation had an acceptable error compared with the experimental results, with a global average error of 9%, showing that the predictive modelling based on the multiscale method is suitable for the design process of this kind of composite.

Pollutant Transport Model and Numerical Simulation in Landfill Site

2012 ◽  
Vol 443-444 ◽  
pp. 424-429
Author(s):  
Ying Zhao ◽  
Qiang Xue ◽  
Lei Liu ◽  
Bing Liang
Keyword(s):  
Numerical Simulation ◽  
Control System ◽  
Simulation Model ◽  
Landfill Leachate ◽  
Transport Model ◽  
Control Measure ◽  
Underground Water ◽  
Seepage Control ◽  
Simulation Results ◽  
The One

The simulation model for describing the transportation and transformation of landfill leachate pollutant in landfill, soil and underground water was established. Taking Wuhan Changshankou landfill for example, the numerical simulation was carried out. The simulation results showed that if there’s no any seepage control measure, the groundwater and soil under landfill will be polluted seriously after MSW was filled; the highest pollutant concetration in landfill was about 25000, and the one in groundwater and soil was about 20000; at the thirtieth year, the pollutant concetration in groundwater and soil still remained up to 10000 although the one in landfill was about 0. The simulation results also showed that the vertical stonewall can’t be used as a nature, and artificial seepage control system must be used.

scholarly journals Impact of frozen soil processes on soil thermal characteristics at seasonal to decadal scales over the Tibetan Plateau and North China

2020 ◽  
Author(s):  
Qian Li ◽  
Yongkang Xue ◽  
Ye Liu
Keyword(s):  
Tibetan Plateau ◽  
Soil Temperature ◽  
Temperature Profile ◽  
Land Surface ◽  
North China ◽  
Thermal Characteristics ◽  
Frozen Soil ◽  
The Tibetan Plateau ◽  
Soil Processes ◽  
Freeze Thaw

Abstract. Frozen soil processes are of great importance in controlling surface water and energy balances during the cold season and in cold regions. Over recent decades, considerable frozen soil degradation and surface soil warming have been reported over the Tibetan Plateau and North China, but most land surface models have difficulty in capturing the freeze-thaw cycle and few validations focus on the effects of frozen soil processes on soil thermal characteristics in these regions. This paper addresses these issues by introducing a physically more realistic and computationally more stable and efficient frozen soil module (FSM) into a land surface model—the third-generation Simplified Simple Biosphere model (SSiB3-FSM). To overcome the difficulties in achieving stable numerical solutions for frozen soil, a new semi-implicit scheme and a physics-based freezing-thawing scheme were applied to solve the governing equations. The performance of this model, as well as the effects of frozen soil process on the soil temperature profile and soil thermal characteristics, were investigated over the Tibetan Plateau and North China using observation and models. Results show that the SSiB3 model with the FSM produces more realistic soil temperature profile and its seasonal variation than that without FSM during the freezing and thawing periods. The freezing process in soil delays the winter cooling, while the thawing process delays the summer warming. The time lag and amplitude damping of temperature become more pronounced with increasing depth. These processes are well simulated in SSiB3-FSM. The freeze-thaw processes could increase the simulated phase lag days and land memory at different soil depths, as well as the soil memory change with the soil thickness. Furthermore, compared with observations, SSiB3-FSM produces a realistic change of maximum frozen soil depth at decadal scales. This study shows the soil thermal characteristics at seasonal to decadal scales over frozen ground can be greatly improved in SSiB3-FSM and SSiB3-FSM can be used as an effective model for TP and NC simulation during cold reasons.

The Analysis of Temperature and Displacement Coupling in Freeze-Thaw Process of Soil

2011 ◽  
Vol 97-98 ◽  
pp. 192-198
Author(s):  
Shu Guang Hou
Keyword(s):  
Numerical Simulation ◽  
Temperature Field ◽  
Numerical Computation ◽  
Geometric Model ◽  
Simulation Method ◽  
Frozen Soil ◽  
Displacement Fields ◽  
Soil Frost ◽  
Freeze Thaw ◽  
Thaw Settlement

Through the coupling analysis of temperature and displacement fields in freeze-thaw process of soil by ABAQUS software, a numerical simulation method of the two fields coupling in freeze-thaw process of soil is put forward. In computation, the temperature field is analyzed firstly, and then the physico-mechanical parameters are defined as functions of temperature field. The geometric model and boundary conditions of numerical simulation are identical with these in laboratorial tests. By comparing the computation results of soil freeze-thaw process with its laboratorial test results, it was found that on the curve of soil freeze-thaw process obtained from laboratorial tests there is a short frost-swelling phenomenon at the initial stage of freeze-thaw process, and then is continuous thaw condition, but on the numerical computation curve, the reflect of soil frost swelling stage isn’t obvious. With the exception of this the numerical computation result and laboratorial test result are more identical. The frost-swelling quantum is very small, so the main expression of overall deformation of soil is thaw-settlement deformation. Therefore the frost swelling phenomenon doesn’t influence the end quantum of settlement. For this reason, the computing method introduced in this paper can be used to conduct numerical simulation of the thaw-settlement of frozen soil and to a certain extent guide the designs of subgrade and pavement in permafrost zones.

scholarly journals Numerical Simulation Analysis of Hydrothermal Change of Subgrade by Seepage Drainage Geogrid Under the Effect of Asphalt Mixture Freeze-Thaw Action

2021 ◽  
Author(s):  
Fang Wang
Keyword(s):  
Numerical Simulation ◽  
Model Test ◽  
Simulation Analysis ◽  
Asphalt Mixture ◽  
Frozen Soil ◽  
Experimental Comparison ◽  
Freeze Thaw ◽  
Subgrade Soil ◽  
Seasonal Frozen Soil ◽  
Drainage Effect

In seasonal frozen soil area, the engineering problems caused by the excessive moisture content of the subgrade soil are widespread. In view of this phenomenon, author proposes to employ a new type of research and development of the seepage drainage geogrid (SDG) to cool and drain the soil. Through indoor model test, after two freeze-thaw cycles, the experimental comparison of the size and laying method of various SDG was carried out. The test result shows that the model with a natural grit layer has the most drainage effect. While, the model contains two layers of interconnected grilles has the best cooling effect. The indoor model test is simulated by accurate numerical simulation. The simulation results are compared with the indoor test results. The fitting results of the two results are very high, which provides theoretical support and data guarantee for the application of seepage drainage grille to strengthen the roadbed in the cold road.

Structure Information From Electron Diffraction Intensities

1990 ◽  
Vol 48 (2) ◽  
pp. 516-517
Author(s):  
J. Gjønnes ◽  
N. Bøe ◽  
K. Gjønnes
Keyword(s):  
Computational Effort ◽  
Unit Cell ◽  
Small Unit ◽  
Structure Information ◽  
Dispersion Surface ◽  
Integrated Intensity ◽  
The One ◽  
Image Position ◽  
Convergent Beam ◽  
Beam Patterns

Structure information of high precision can be extracted from intentsity details in convergent beam patterns like the one reproduced in Fig 1. From low order reflections for small unit cell crystals,bonding charges, ionicities and atomic parameters can be derived, (Zuo, Spence and O’Keefe, 1988; Zuo, Spence and Høier 1989; Gjønnes, Matsuhata and Taftø, 1989) , but extension to larger unit cell ma seem difficult. The disks must then be reduced in order to avoid overlap calculations will become more complex and intensity features often less distinct Several avenues may be then explored: increased computational effort in order to handle the necessary many-parameter dynamical calculations; use of zone axis intensities at symmetry positions within the CBED disks, as in Figure 2 measurement of integrated intensity across K-line segments. In the last case measurable quantities which are well defined also from a theoretical viewpoint can be related to a two-beam like expression for the intensity profile:With as an effective Fourier potential equated to a gap at the dispersion surface, this intensity can be integrated across the line, with kinematical and dynamical limits proportional to and at low and high thickness respctively (Blackman, 1939).

scholarly journals Scenario Analyses of Exhaust Emissions Reduction through the Introduction of Electric Vehicles into the City

Energies ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 2030
Author(s):  
Marianna Jacyna ◽  
Renata Żochowska ◽  
Aleksander Sobota ◽  
Mariusz Wasiak
Keyword(s):  
Inner City ◽  
Electric Vehicles ◽  
Transport Model ◽  
Exhaust Emissions ◽  
Scenario Analyses ◽  
High Emission ◽  
Clean Air ◽  
The One ◽  
The City

In recent years, policymakers of urban agglomerations in various regions of the world have been striving to reduce environmental pollution from harmful exhaust and noise emissions. Restrictions on conventional vehicles entering the inner city are being introduced and the introduction of low-emission measures, including electric ones, is being promoted. This paper presents a method for scenario analysis applied to study the reduction of exhaust emissions by introducing electric vehicles in a selected city. The original scenario analyses relating to real problems faced by contemporary metropolitan areas are based on the VISUM tool (PTV Headquarters for Europe: PTV Planung Transport Verkehr AG, 76131 Karlsruhe, Germany). For the case study, the transport model of the city of Bielsko-Biala (Poland) was used to conduct experiments with different forms of participation of electric vehicles on the one hand and traffic restrictions for high emission vehicles on the other hand. Scenario analyses were conducted for various constraint options including inbound, outbound, and through traffic. Travel time for specific transport relations and the volume of harmful emissions were used as criteria for evaluating scenarios of limited accessibility to city zones for selected types of vehicles. The comparative analyses carried out showed that the introduction of electric vehicles in the inner city resulted in a significant reduction in the emission of harmful exhaust compounds and, consequently, in an increase in the area of clean air in the city. The case study and its results provide some valuable insights and may guide decision-makers in their actions to introduce both driving ban restrictions for high-emission vehicles and incentives for the use of electric vehicles for city residents.

scholarly journals A simple model for predicting soil temperature in snow-covered and seasonally frozen soil: model description and testing

2004 ◽  
Vol 8 (4) ◽  
pp. 706-716 ◽  
Author(s):  
K. Rankinen ◽  
T. Karvonen ◽  
D. Butterfield
Keyword(s):  
Heat Capacity ◽  
Simple Model ◽  
Soil Temperature ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Frozen Soil ◽  
Model Description ◽  
Freezing And Thawing ◽  
Catchment Scale ◽  
Soil Temperatures

Abstract. Microbial processes in soil are moisture, nutrient and temperature dependent and, consequently, accurate calculation of soil temperature is important for modelling nitrogen processes. Microbial activity in soil occurs even at sub-zero temperatures so that, in northern latitudes, a method to calculate soil temperature under snow cover and in frozen soils is required. This paper describes a new and simple model to calculate daily values for soil temperature at various depths in both frozen and unfrozen soils. The model requires four parameters: average soil thermal conductivity, specific heat capacity of soil, specific heat capacity due to freezing and thawing and an empirical snow parameter. Precipitation, air temperature and snow depth (measured or calculated) are needed as input variables. The proposed model was applied to five sites in different parts of Finland representing different climates and soil types. Observed soil temperatures at depths of 20 and 50 cm (September 1981–August 1990) were used for model calibration. The calibrated model was then tested using observed soil temperatures from September 1990 to August 2001. R2-values of the calibration period varied between 0.87 and 0.96 at a depth of 20 cm and between 0.78 and 0.97 at 50 cm. R2-values of the testing period were between 0.87 and 0.94 at a depth of 20cm, and between 0.80 and 0.98 at 50cm. Thus, despite the simplifications made, the model was able to simulate soil temperature at these study sites. This simple model simulates soil temperature well in the uppermost soil layers where most of the nitrogen processes occur. The small number of parameters required means that the model is suitable for addition to catchment scale models. Keywords: soil temperature, snow model

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