scholarly journals Temperature Distribution of Railway Tunnels in Winter

2021 ◽  
Vol 21 (1) ◽  
pp. 199-205
Author(s):  
YoonSik Park ◽  
SeHee Lee ◽  
KookHwan Cho
Keyword(s):  
Temperature Distribution ◽  
Influence Factor ◽  
Concrete Slab ◽  
Freezing Temperature ◽  
Tunnel Lining ◽  
Freezing Range ◽  
External Temperature ◽  
Slab Track ◽  
Train Operation ◽  
Tunnel Entrance

The freezing water around the tunnel lining, which is caused by the external temperature during winter, damages portions of tunnel structures, such as the lining and concrete slab track. To investigate the influence of freezing temperature, a total of 50 temperature gauges were installed from the tunnel entrance to 3,270 m. The total length of the tunnel was 8,293 m. The variation in temperature along the tunnel was measured during winter. The correlation between the variation in temperature and the influence of train operation at a speed of 130-150 km/h was analyzed. The duration of the increasing freezing temperature range influenced by train operation was also analyzed and displayed in the results. The results demonstrated that the variation in temperature according to the train operation could be recovered in 30 min. Therefore, when considering the freezing range of a tunnel where trains are travelling at intervals of approximately 30 min, it was judged that the influence factor will be negligible owing to the train operation.

IMPACT OF EXTERNAL TEMPERATURE DISTRIBUTION ON THE TURBULENT AND THERMAL FIELDS IN A VERTICAL UNIFORMLY HEATED CHANNEL

2018 ◽  
Author(s):  
Martin Thebault ◽  
Stephanie Giroux-Julien ◽  
Victoria Timchenko ◽  
Christophe Menezo ◽  
John Reizes
Keyword(s):  
Temperature Distribution ◽  
External Temperature ◽  
Thermal Fields ◽  
Heated Channel

scholarly journals Temperature distribution in a permafrost-affected rock ridge from conductivity and induced polarization tomography

2020 ◽  
Author(s):  
P-A Duvillard ◽  
F Magnin ◽  
A Revil ◽  
A Legay ◽  
L Ravanel ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Temperature Distribution ◽  
Thermal State ◽  
Low Cost ◽  
Freezing Temperature ◽  
Induced Polarization ◽  
Rock Surface ◽  
European Alps ◽  
Limited Information ◽  
Polarization Tomography

Summary Knowledge of the thermal state of steep alpine rock faces is crucial to assess potential geohazards associated with the degradation of permafrost. Temperature measurements at the rock surface or in boreholes are however expensive, invasive, and provide spatially-limited information. Electrical conductivity and induced polarization tomography can detect permafrost. We test here a recently developed petrophysical model based on the use of an exponential freezing curve applied to both electrical conductivity and normalized chargeability to infer the distribution of temperature below the freezing temperature. We then apply this approach to obtain the temperature distribution from electrical conductivity and normalized chargeability field data obtained across a profile extending from the SE to NW faces of the lower Cosmiques ridge (Mont Blanc massif, Western European Alps, 3613 m a.s.l., France). The geophysical datasets were acquired both in 2016 and 2019. The results indicate that the only NW face of the rock ridge is frozen. To evaluate our results, we model the bedrock temperature across this rock ridge using CryoGRID2, a 1D MATLAB diffusive transient thermal model and surface temperature time series. The modelled temperature profile confirms the presence of permafrost in a way that is consistent with that obtained from the geophysical data. Our study offers a promising low-cost approach to monitor temperature distribution in Alpine rock walls and ridges in response to climate change.

scholarly journals Thermal distribution analysis of inner defects in TSV

2018 ◽  
Vol 38 ◽  
pp. 04026
Author(s):  
Chuan Kai Jiang ◽  
Lei Nie ◽  
Wen Jia ◽  
Yu Ning Zhong
Keyword(s):  
Thermal Analysis ◽  
Finite Element ◽  
Temperature Distribution ◽  
Temperature Variation ◽  
Finite Element Models ◽  
Distribution Analysis ◽  
Internal Defects ◽  
External Temperature ◽  
Thermal Distribution ◽  
Distinct Temperature

In order to uncover the external manifestations of TSV internal defects, the finite element models of typical internal defects, which were filling missing, axial cavity and end cavity, were established. The thermal analysis was carried out using thermoelectric coupling method. The temperature distribution of TSV with and without defects were obtained. And the temperature variation profiles on the defined paths of TSV layer were also analyzed. The analysis indicated that all the defective TSV showed distinct temperature distribution with the defect-free TSV. Among three typical defects, TSV with filling missing showed the most obvious difference on the temperature distribution and path variation. TSV with end cavity has relatively weak affect and the slightest defect was TSV with axial cavity. Therefore, it could be seen that the external temperature difference caused by the internal defects of TSV could provide effective information for the identification and detection in TSV with internal defects.

Effect of rail pad stiffness on the wheel/rail force intensity in a railway slab track with short-wave irregularity

2019 ◽  
Vol 233 (10) ◽  
pp. 1038-1049 ◽  
Author(s):  
Amin Khajehdezfuly
Keyword(s):  
High Frequency ◽  
Critical Speed ◽  
Concrete Slab ◽  
Low Frequency ◽  
Short Wave ◽  
Vehicle Speed ◽  
Frequency Range ◽  
Slab Track ◽  
High Frequency Excitation ◽  
Frequency Excitation

In this paper, a two-dimensional numerical model is developed to investigate the effect of rail pad stiffness on the wheel/rail force in a slab track with harmonic irregularity. The model consists of a vehicle, nonlinear Hertz spring, rail, rail pad, concrete slab, resilient layer, concrete base, and subgrade. The rail is simulated using the Timoshenko beam element for considering the effects of high-frequency excitation produced by short-wave irregularity. The results obtained from the model are compared with those available in the literature and from the field to prove the validity of the model. Through a parametric study, the effect of variations in rail pad stiffness, vehicle speed, and harmonic irregularity on the wheel/rail force is investigated. For the slab track without any irregularity, the wheel/rail force is at maximum when the vehicle speed reaches the critical speed. As the rail pad stiffness increases, the critical speed increases. When the amplitude of irregularity is high, wheel jumping phenomenon may occur. In this situation, as the vehicle speed and rail pad stiffness are increased, the dynamic wheel/rail force is increased. In the low-frequency range, the wheel/rail force increases as the rail pad stiffness increases. In the high-frequency range, the wheel/rail force increases as the rail pad stiffness is decreased.

scholarly journals Experimental and Theoretical Determination of the Frost-Heave Cracking Law and the Crack Propagation Criterion of Slab Track with Water in the Crack

2019 ◽  
Vol 9 (21) ◽  
pp. 4592 ◽  
Author(s):  
Fengzhuang Tong ◽  
Liang Gao ◽  
Xiaopei Cai ◽  
Yanglong Zhong ◽  
Wenqiang Zhao ◽  
...  
Keyword(s):  
Crack Initiation ◽  
Crack Propagation ◽  
Crack Opening ◽  
Evaluation Criteria ◽  
Image Correlation ◽  
Frost Heave ◽  
External Temperature ◽  
Slab Track ◽  
Initiation And Propagation ◽  
Evolution Laws

Crack propagation produced by frost heave affects the durability of slab-track structures in high-humidity and cold regions in China. This work is intended to reveal the evolution laws of frost-heave crack propagation, establish evaluation criteria for crack propagation, and investigate factors involved in frost-heave crack propagation. Firstly, by preparing slab-track specimens with initial cracks, an experiment of frost-heave crack propagation was designed. The process of frost-heave crack propagation was carried out by means of digital image correlation (DIC) technology and acoustic emission (AE) technology, respectively. These experiments revealed the evolution laws of generalized strain and AE events’ location during crack initiation and propagation, respectively, and the key parameters of micro-crack initiation strain and unstable propagation strain were obtained. By using theoretical and experimental analysis, a double-strain criterion for frost-heave crack propagation was proposed. Finally, factors involved in frost-heave crack propagation were investigated. The results show that crack initiation can be reflected by the crack-tip strain. The average micro-crack initiation strain and unstable propagation strain were found to be 224 με and 243 με, respectively. Moreover, it was found that the frost-heave crack propagation was caused by an ice plug which formed at the crack opening. When the crack width is larger than 2.7 mm and the external temperature is lower than −6.6 °C, cracks propagate easily under the frost-heave force.

Leak Localization Algorithm Applied to Non-Isothermal Liquid Flow in Horizontal Pipelines

2018 ◽  
Author(s):  
Aline Figueiredo ◽  
Carina N. Sondermann ◽  
Rodrigo A. C. Patricio ◽  
Raphael Viggiano ◽  
Gustavo C. R. Bodstein ◽  
...  
Keyword(s):  
Temperature Distribution ◽  
Liquid Flow ◽  
Heat Transfer Process ◽  
Isothermal Flow ◽  
Localization Algorithm ◽  
External Temperature ◽  
Oil Pipeline ◽  
Localization Model ◽  
Localization Strategy ◽  
Leak Localization

In the oil industry liquid pipelines are very important for the transport of liquids, particularly in long offshore pipelines. The operation of these oil pipelines is susceptible to the occurrence of leaks in the system. Localizing a leak in a very long oil pipeline is an important piece of information that needs to be obtained before mitigating actions can be taken. These pipelines are usually subject to the temperature gradients that exist in the bottom of the ocean, and the resulting heat transfer process may lead to wax formation and deposition. The single-phase flow that occurs in this type of offshore pipeline that presents one leak point and suffers the effects of an external temperature gradient is numerically simulated in this paper. We consider a one-dimensional mathematical model that includes conservation equations of mass, momentum and energy, and its associated numerical method to calculate the transient liquid flow inside the pipeline. We are particularly interested in testing a leak localization model based upon the intersection of the hydraulic grade lines emanating from the pipeline ends under the influence of a non-zero temperature distribution. This paper proposes to compare the results for a non-isothermal flow with the corresponding isothermal flow to study the influence of the temperature distribution upon the leak localization strategy. The flow that develops along the entire pipeline, upstream and downstream of the leak, strongly affects the pressure gradient and has a significant influence on the location of the leak. Our numerical simulations show results that allow the model sensitivity to be studied by changing the leak magnitude, for a given leak position. From this analysis, we may observe how these parameters affect the pressure gradients along the pipeline that develop upstream and downstream of the leak and the model’s ability to predict the leak location.

Numerical Analysis of Temperature Distribution throughout a Concrete Slab during Fire Using a Web-Based Solver

2020 ◽  
Vol 309 ◽  
pp. 149-156
Author(s):  
Jakub Holan ◽  
Radek Štefan
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Computational Algorithm ◽  
Concrete Slab ◽  
Initial Density ◽  
Slab Thickness ◽  
Solid Materials ◽  
Web Based ◽  
User Friendly ◽  
Numerical Approaches

The problem of heat transfer in solid materials can be described by the well known transient heat transfer equation. However, as the problem is strongly non-linear, the solution to this equation generally cannot be determined directly. Various numerical approaches have been proposed and employed by various authors for solving the problem.However, most of the available numerical solvers are limitedly available as they are often not free to use, they have to be installed, and they are too complex.This paper presents a new web-based solver for the problem of heat transfer over the thickness of a concrete slab during fire developed by the authors.The computational algorithm is based on the finite difference method and implemented using JavaScript.A graphical user interface for the input of user-defined parameters and for the interpretation of results is created using HTML.The paper also briefly presents the theory behind the computational algorithm.Moreover, examples of various problems solved by the web-based solver are presented in the paper.A brief parametric study of the effect of initial density of the material on the temperature distribution in the slab during fire is also presented. From the presented figures and examples, it can be readily seen that the newly developed web-based solver for the assessment of temperature distribution over a slab thickness during fire is user-friendly, easy to use, highly accessible, fast, and intuitive.

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