Science and Transport Progress

Modeling of Filtration and Heat and Mass Transfer Processes in Groundwater

2024-10-18T10:28:45+03:00

Purpose. The method of mathematical modeling is an important tool for solving complex problems involving the analysis of groundwater dynamics and heat and mass transfer processes in them when studying their contamination from various anthropogenic sources in the event of accidental spills of chemically hazardous substances, etc. The main purpose of the article is to develop a set of mathematical models for calculating the process of filtration of non-pressure groundwater, mass transfer of impurities and the process of heat transfer in groundwater. Methodology. The two-dimensional Boussinesq equation of filtration was used to predict the dynamics of groundwater. The two-dimensional equation of convective-diffusive transport of impurities was used to model the processes of mass transfer in groundwater. The process of freezing of individual sections of the groundwater flow is modeled using the Laplace equation for the velocity potential (calculation of the flow velocity field in a time-varying geometry) and the two-dimensional equation of heat transfer in groundwater. Finite difference schemes were used to solve the modeling equations of groundwater dynamics and heat and mass transfer. Findings. A set of mathematical models has been developed to calculate the process of filtration of non-pressure groundwater and its chemical contamination. The experiment has confirmed the adequacy of the constructed numerical model of filtration of a non-pressure groundwater flow. An effective mathematical model was developed that allows determining the temperature fields in groundwater during the operation of a well used to freeze certain sections of the flow. The results of computer modeling indicate the effectiveness of the developed mathematical models. Originality. Effective mathematical models for predicting the level of chemical contamination of groundwater, its dynamics and thermal regime are proposed. The constructed mathematical models make it possible to determine the dynamics of changes in the temperature regime of groundwater during the operation of wells through which refrigerant is supplied to freeze individual areas. A computer program has been developed that allows for a comprehensive assessment of groundwater conditions. Practical value. A set of computer programs has been developed to conduct a computational experiment to study the processes of filtration, chemical contamination of groundwater and heat transfer processes in them. This set of programs can be used for the scientific substantiation of engineering solutions aimed at protecting groundwater.

Predicting the Consequences of an Emergency at a Railway Station

2024-10-08T13:11:19+03:00

Purpose. The paper considers the problem of determining the size of the damage zones in the event of an emergency at a railway station due to a tanker fire. The task of forecasting is to determine the zones of thermal pollution, as well as chemical and mechanical pollution. The main objective of the study is to create numerical models for calculating the zones of mechanical and thermal pollution in the event of a fire at a railway station. Methodology. To analyze the size and intensity of zones of thermal, chemical, and mechanical environmental pollution in the event of an extreme situation at a railway station, we used the equations of heat and mass transfer and Newton's second law for modeling mechanical environmental pollution. To solve the equations, numerical methods such as Euler's method and finite difference schemes were used. On the basis of the developed numerical models, a computer code was created to conduct a computational experiment. Findings. Modern computer models for assessing the zones of chemical, thermal, and mechanical pollution in the event of an extreme situation have been developed. The results of computer modeling are presented. Originality. A set of numerical models for computer simulation of heat and mass transfer processes and dynamics of point motion has been created, which allows conducting a computational experiment to determine the contamination zones during a fire at a railway station. Practical value. A computer code was developed on the basis of the created mathematical models. This code is a tool for solving important problems in the field of environmental safety and civil protection. The computer code makes it possible to quickly determine the intensity and size of environmental pollution zones in the event of an extreme situation.

Investigation of the Influence of a Turnout Cross on Vertical and Horizontal Deformations of a Pneumatic Spring of High-Speed Rolling Stock

2024-10-08T13:42:00+03:00

Purpose. The aim of the study is to determine the values of vertical and horizontal deformations of the pneumatic spring of high-speed rolling stock during the movement of the test setup along the cross of the switch in the forward and reverse directions. Methodology. To determine the deformations of the pneumatic spring, a special test bench consisting of a pneumatic spring and specialized measuring equipment was developed. The deformations of the air spring in the vertical and horizontal planes were measured using high-frequency potentiometric linear displacement sensors, the signals from which were read using a programmed analog-to-digital converter. To obtain reliable data on the deformations of the air spring, six passes of the test bench were made in the forward and reverse directions of the cross member. Findings. A methodology for dynamic testing of a pneumatic spring of high-speed rolling stock under conditions of movement along the crosshead of a turnout in the forward and reverse directions was developed. The records of vertical and horizontal deformations of the pneumatic spring of high-speed rolling stock under the conditions of movement along the crossover of a switch were obtained. It is established that the deformations of the pneumatic spring in the vertical plane are higher than those in the horizontal plane. The average value of the vertical deformations of the pneumatic spring in the forward direction is 3.15 mm, which is 9.98 % higher than the average value in the opposite direction of the test unit's movement along the cross-section of the switch. In the horizontal direction, this difference in deformation of the air spring is 25.1 %. Originality. For the first time, the vertical and horizontal deformations of the pneumatic spring of high-speed rolling stock under the conditions of movement along the crossbar of a switch were determined, taking into account the direction of movement, forward and reverse. Practical value. Determining the values of deformations of the pneumatic spring will allow to study its dynamic characteristics in different operating conditions of rolling stock, and at the design stage to select the appropriate characteristics of the pneumatic spring suspension system and determine the dynamic and safety indicators of rolling stock.

Design Features of a Removable Module for Securing Containers in Gondola Cars

2024-10-15T10:56:25+03:00

Purpose. The main purpose of the study is to highlight the design features of the design of a removable module for fastening containers in gondola cars. Methodology. For the safe transportation of containers in gondola cars, it is proposed to use a removable module. This module operates on the principle of an intermediate adapter between the container and the open wagon body. The choice of the profiles of the beams of the frame of the removable module was made according to the moments of resistance of their components. To do this, the core system of the removable module frame was constructed and calculated using the Lira CAD software package. According to the maximum bending moment acting in the module frame due to the moment of resistance and the known permissible stresses, the profile of the frame beams was selected. Taking into account the selected profile of the frame, its spatial model was built and strength calculations were performed. The finite element method implemented in SolidWorks Simulation was used for strength calculations. The calculation was carried out for two loading schemes of the removable module: the effect of a vertical load and the effect of vertical and longitudinal loads. Findings. Based on the calculation, the profile of the removable module was selected according to the determined value of the resistance moment - a square pipe with a height and width of 300 mm and a wall thickness of 5 mm. The results of the strength calculations of the removable module showed that for the case of its perception of a vertical load, the maximum stresses are 112.5 MPa. The maximum displacements occur in the upper parts of the superstructures and are about 1 mm. For the case of the vertical and longitudinal loads perceived by the removable module, the maximum stresses in its structure amounted to 287.6 MPa. The maximum displacements occurred in the end superstructure located on the side of the load applied to the removable module. These displacements amounted to 2.16 mm. Thus, the strength of the removable module for the considered loading schemes is ensured. Originality. A scientific approach to the design of a removable module for securing containers in gondola carsis proposed. Practical value. The research will contribute to the creation of recommendations for the design of modular-type vehicle structures, as well as to improving the efficiency of railway transport operation.

Analysis of the Influence of Machine Operation Parameters on the Technical Characteristics of the Elevator in the Point of Cleaning and Washing of the Equipment Park

2024-10-08T12:53:12+03:00

Purpose. The study is aimed at determining the nature of the influence of the operating parameters of the enterprise's machines (the number of tracked and wheeled machines, the annual consumption rates of their motor resources) on the technical characteristics of the elevator for cleaning the dirt settler of the vehicle cleaning and washing equipment park, in particular, the height of the elevator and its productivity, as well as building analytical and graphical dependencies of these values on the operating parameters of the machinery. Methodology. To achieve this goal, we used the calculation algorithms presented in the modern technical literature and analyzed the factors and values that affect the height and capacity of the elevator of the station. It has been established that in order to determine the design parameters of the elevator, it is necessary to have statistical data on the operation of machinery at the enterprise and to carry out a detailed calculation, which includes: the mathematical expectation of the average daily number of machine trips from the fleet for different types of machinery, as well as the total value, the number of numbered machine servicing, the number of external machine washing stations, and the geometric parameters of the dirt tank. Findings. A graphical analysis of the influence of the number of tracked and wheeled vehicles and their annual consumption rates of motor resources on the value of its height and productivity was carried out for the elevator of the cleaning and washing station of the fleet of a particular enterprise, which is intended for cleaning the sludge tank. It was found that the functions of change in productivity and height are linearly increasing (with other parameters fixed). Originality. The authors first investigated the dependencies of the design parameters (height and capacity) of the elevator, built analytical dependencies of the mathematical expectation of the average daily number of machine trips for wheeled and tracked vehicles on the number of relevant machines and annual motor resource consumption rates, as well as the height and capacity of the elevator. For the examples of enterprise fleets with equipment operation parameters taken from statistical data, a graphical analysis of the constructed dependencies was carried out. Practical value. The use of the constructed dependencies makes it possible to determine the general nature and range of changes in the above design parameters in the case of varying equipment performance at a particular enterprise. The proposed dependencies can be used to quickly determine the required design parameters of an elevator based on specific data on the operation of equipment.

Clarification of the Methodology for Determining the Characteristics of Cable Cars

2024-10-15T14:32:26+03:00

Purpose. The aim of this study is to clarify the methodology and develop an algorithm for determining the characteristics of cable cars of traditional design and with self-propelled cars, taking into account new factors of influence. Methodology. An analysis of existing methods for determining the characteristics of cable cars of various designs was carried out. This goal was achieved by taking into account the weight of the individual drive and the actual angle of the car's elevation relative to the horizon for a self-propelled car; the influence of the coefficient of adhesion of the rope to the tension pulley and the angle of envelopment of the rope around the tension pulley for a traditional cable car. To determine the required drive power of a cable car with self-propelled cars, the influence of the weight of an individual self-propelled car drive and the actual angle of the self-propelled car relative to the horizon are taken into account by the method of force analysis. For traditional cable cars, the contour traversal method is used, which takes into account the coefficient of adhesion of the rope to the tension pulley, as well as the angle of envelopment of the tension pulley by the rope. Findings. The dependencies of the required drive power on the design parameters of the cable car were obtained, taking into account new factors of influence. The choice of a specific methodology for calculating the required power is justified in accordance with the selected type of road and the initial data. The results obtained can be supplemented by performing additional calculations using the formulas given in this paper. The presented algorithms for determining the characteristics of a cable car using the refined methodology allow, at the programming level, to develop software for accurately calculating the value of the required drive power. Originality. The dependence of the required drive power on the characteristics of the cable car was clarified by taking into account additional factors, which made it possible to more accurately assess their impact on the final result. Practical value. The results of this work can be used in the design of energy-efficient cable cars, for which the electric motor is selected according to a refined methodology that takes into account more factors affecting the required drive power.

Research of the Primary Electric Energy Storage System of a Traction Photovoltaic Module

2024-10-22T12:01:46+03:00

Purpose. The main idea of the work is that the electric energy generated by photovoltaic installations is supplied in small parts to capacitive energy storage devices of low power, and then these «portions» of energy are supplied to one common, so-called traction storage device. The research is aimed at obtaining time diagrams of current and voltage changes in the proposed system. Methodology. A review of the world literature on the topic of work was conducted. The basis of this research is the analysis of transient processes in the electrical circuits of the system during the transfer of energy from the photovoltaic module to the traction capacitor under the influence of various control signals: series, parallel, combined. The main research method is computer simulation. The Scilab software environment was used to simulate the operation of the electric energy storage system. Findings. The relevance of the research and development of a primary electric energy storage system using a traction photovoltaic module has been proved. The key mathematical dependencies between the parameters of the constituent elements of electrical circuits are established. The structure of a site with electric energy storage with traction photovoltaic modules and a converter-pulse signal unit is proposed. The graphical characteristics of transient processes that occurred during the transfer of energy from low-power capacitive elements to a high-power capacitive element (traction capacitor) were obtained. Originality. For the first time, graphical dependences of energy transfer between system elements were obtained, which allows for a reasonable choice of the parameters of these elements. Also, for the first time, time dependencies describing the law of control of the process of energy transfer between system links were obtained, which will allow determining the rational modes of its operation. Practical value. The results of the research open up new opportunities in the research field in the development of large-scale experimental models of the maglev path structure in the case of the introduction of a system of distributed primary energy storage in a traction photovoltaic module.

Contextual Analysis of the Site

2024-10-16T12:35:47+03:00

Purpose. The purpose of this article is to describe the method of contextual website research, which is an alternative to traditional benchmark tests. Unlike laboratory tests, where conditions are strictly controlled, contextual research allows you to evaluate the usability of a website in a real context, taking into account the factors that affect the user in his or her usual environment. This means that researchers observe users interacting with a website in their natural environment, such as at home or at work, which allows them to gain a more relevant understanding of the user experience. Methodology. We used the contextual research method, which involves detailed observation and interviewing a small group of users about certain aspects of a website. This helps to get a realistic picture of how the user perceives and uses the site in real conditions, in the context of websites. Researchers can observe how users use the website, what tasks they are trying to accomplish, what difficulties they encounter, and how they interact with other tools and programs. Findings. The study makes it possible to greatly simplify the evaluation of website usability using certain approaches and developed software. Using contextual research, it is possible to identify shortcomings that would not be noticeable during laboratory tests and suggest improvements that increase the usability of a website. Originality. The study is based on key principles such as contextualization, collaborative evaluation, usability as the main indicator, and focus on the subject matter. This allows us to gain a deeper understanding of how users interact with a website in real life, not just in an artificially created laboratory environment. Practical value. The results of the work allow us to use the method of contextual research in a wide range of human activities within websites of different orientations to improve the user experience. This can be especially useful for websites that are developed for certain groups of users, such as people with disabilities or the elderly.