Course Of Numerical Experiment Research Articles

Оптико-электронная система для оперативного контроля прямолинейности железнодорожных рельсов

The paper considers principles of operation of the optical electronic devices designed for operational high-precision control of the railway rails rolling surface straightness. It provides a description of the functional scheme proposed by the authors of the optical electronic devices of the triangulation type with structured illumination, where the rolling surface straightness is assessed based on analyzing the images of the rail cross sections registered by a linear camera. A technical solution is proposed that could significantly increase control and reliability of its results, as well as ensure image registration of the rail cross sections, where the distance between them is not exceeding 1 mm with the measurement car speed of 180 km/h. Mathematical expressions were obtained to study the optical electronic devices proposed scheme influence on the threshold sensitivity of control over the points' position along the rail rolling surface. To reduce the control results error, methods of the coordinates' subpixel refinement of the structured illuminated peaks registered coordinates were used. In the course of numerical experiments, the error root-mean-square deviation dependence in measuring the rail surface points' coordinates on the signal-to-noise ratio and the structured illumination peaks width values was studied. Requirements are formulated to components of the triangular type optical electronic devices, which could be introduced in design and development of the high-precision equipment for operational control of the railway track rolling stock straightness

Исследование влияния температурного режима пожара на эффективность вспучивающегося огнезащитного покрытия, предназначенного для огнезащиты стальных конструкций

Introduction. The usage of intumescent coating (hereinafter referred to as IC) is justified by the development of a fire protection project, taking into account the data on its fire protection efficiency, estimated under the influence of standard temperature conditions, the usage of which can lead to overestimating the fire resistance margin in the project or underestimating the thermal impact on the steel building structures with IC fire protection in conditions of a real fire. Aims and purposes. The purpose of the study is to evaluate the effect of fire temperature conditions on the effectiveness of IC. To achieve this goal, the following tasks were carried out: a temperature mode of fire in a building under different fire loads by the example of a warehouse building was estimated; experiments to estimate the influence of different heat fluxes, reduced thickness of metal and IC thickness on its effectiveness by the full factor experiment of the type 2 were conducted. Methods. To mathematically simulate real temperature fires, the Fire Dynamics Simulator (FDS) software package, which implements a field (differential) mathematical model, was used. To study the effect of the obtained fire temperature regimes on the effectiveness of IC, experiments were carried out according to the plan of a complete factor experiment type 2. The test specimens were carbon steel metal plates with dimensions of 100 × 100 mm with reduced thickness of 3 and 4.5 mm and painted with 0.25 and 0.5 mm organic-based single-component IC. A radiant heat flux panel with a radiant heat flux density of 10 to 50 kW/m2 was used to assess the effects of heat flux. Results and discussion. In the course of numerical experiments in the FDS software package, it was found that the thermal impact on steel building structures during a fire can differ significantly from the standard temperature regime, both upwards and downwards. The results of the experiment showed that the heating time of the test samples had the greatest influence of the actors under consideration (the value of the heat flux, the reduced thickness of the metal, the thickness of IC) had the value of the heat flux, as the largest absolute value of the regression equation was obtained. Conclusion. The assumption of possible underestimation of the thermal effect under “standard” temperature conditions on the fire resistance of steel building structures with IC fire protection was confirmed by the tests.

Algebraic Methods for Achieving Super-Resolution by Digital Antenna Arrays

The actual modern problem of developing and improving measurement and observation systems (including robotic ones) is to increase the volume and quality of the information received. Increasing the angle resolution to values significantly exceeding the Rayleigh criterion, i.e. achieving super-resolution is one of important ways to solve the problem. Angular super-resolution which makes it possible to detail images of research objects and their individual fragments, improves the quality of solutions to detection, recognition and identification problems, increases the range of such systems. In many papers methods developed by authors to achieve a super-resolution based on approximate solutions of inverse problems in the form of Fredholm integral equation of the first kind of convolution type called algebraic are presented. The methods used, as well as their varieties, make it possible to reduce solutions of inverse problems posed to solving sets of linear algebraic equations (SLAE). This paper presents results of further improvement of algebraic methods based on intelligent analysis of received signals. It is shown that their use in systems based on digital antenna arrays makes it possible to increase the achieved degree of exceeding the Rayleigh criterion. In the course of numerical experiments with a mathematical model, the stability of the solutions obtained and their adequacy were confirmed. The numerical results obtained open the following possibilities: (1) obtaining images of studied objects with a resolution exceeding the Rayleigh criterion by 4 to 10 times, (2) determining the angular coordinates of individual small-sized objects as part of multi-element complex objects (group targets), (3) clarifying boundaries of extended objects and their individual elements, (4) localizing individual bright objects on a smoothly inhomogeneous reflective background. Applying presented new methods does not require a significant computing power, what allows you to work in a real time mode using relatively simple and inexpensive computing devices. The ways of further improvement of presented algebraic methods for solving applied inverse problems are described.

Numerical Simulation of Temporal Variability of Methane Emissions from Mozhaysk Reservoir

Estimates of methane emission from the Mozhaysk reservoir surface were carried out using the mathematical model LAKE2.3. The average emission value is 361 tC per year, the average flux = 37.7 mgC–CH4 m–2 day–1. Comparison of the obtained estimates with in situ measurements revealed, that the methane emission and specific flux according to the model are in good agreement with the observations data. The ebullition makes the largest contribution to the total emission. During the heating period, an increase of methane emission is observed with a maximum before the autumn mixing stage. In the course of numerical experiments with the model, it was found that the amplitude of methane fluxes into the atmosphere is associated with fluctuations in atmospheric pressure, and the most significant emissions peaks associated with water level drawdowns. Effective method for calibrating the diffusion component of the methane flux into the atmosphere is the potential rate of methane oxidation in the Michaelis-Menten reaction, and for ebullition it is the methane generation parameter in bottom sediments — q10. For the described numerical experiments, the article presents the values of the annual emissions of methane into the atmosphere.

О вопросах верификации результатов моделирования теплового потока полевым методом

Purpose. One of the fire safety requirements is the creation of conditions for preventing fire spread between buildings. This requirement is implemented by observing fire prevention distances (breaks) between buildings and structures. Requirements for fire prevention distances (breaks) are established in regulatory documents. In some cases, the implementation of these requirements is either technically impossible, or associated with significant economic costs, when the further operation of the facility is impractical. To solve this problem, it is possible to reduce fire prevention distances (breaks) between facilities under protection, provided that the engineering calculation confirms the impossibility of fire spread to a neighboring facility by a heat flow. The accuracy of the results obtained by the method of calculating fire distance (break) directly affects the level of fire hazard in the facility under protection, and verification in the calculation models used within the framework of this method is an important stage in its development and improvement. Methods. For research, methods of analysis and computer simulation with the help of the Fire Dynamics Simulator (FDS) software product are used. Findings. The simulation of a heat flow during heptane pan burning is performed. The results obtained during the simulation are compared with the results of a full-scale experiment. Recommendations for setting FDS parameters for heat flow simulation are formulated. Research application field. The study results can be applied in the calculation of fire prevention distances (breaks) by the field method using Fire Dynamics Simulator software product. Conclusions. The model created by means of FDS requires mandatory refinement of the parameters, since not in all cases the default values correctly describe the simulated process. The study of the issue of heat flow simulation in FDS requires further research. In the course of numerical experiments, it is found that when calculating the incident heat flux, it is necessary to pay attention to setting such parameters as discretization of the solid angle, the fraction of energy spent on radiation, CO and soot release. For correct assessment of the incident heat flux, it is recommended to simulate combustion by solid angle correction with a step in 100 until the value of the incident heat flux stabilizes within a narrow range.

Верифікація математичної моделі для розв’язання задачі Стефана в рамках методу “mushy layer”

The use of solar energy has limitations due to its periodic availability: solar plants do not operate at night and are ineffective in dull weather. The solution of this problem involves the introduction of energy storage and duplication systems into the conversion loop. Among the energy storage systems, solid–liquid phase transition modules have significant energy, ecologic, and cost advantages. Physical processes in modules of this type are described by a system of non-stationary nonlinear partial differential equations with specific boundary conditions at the phase interface. The verification of a method for solving the Stefan problem for a heat-storage material is presented in this paper. The use of the mushy layer method made it possible to simplify the classical mathematical model of the Stefan problem by reducing it to a nonstationary heat conduction problem with an implicit heat source that takes into account the latent heat of transition. The phase transition is considered to occur in an intermediate zone determined by the solidus and liquidus temperatures rather than in in infinite region. To develop a Python code, use was made of an implicit computational scheme in which the solidus and liquidus temperatures remain constant and are determined in the course of numerical experiments. The physical model chosen for computer simulation and algorithm verification is the process of ice layer formation on a water surface at a constant ambient temperature. The numerical results obtained allow one to determine the temperature fields in the solid and the liquid phase and the position of the phase interface and calculate its advance speed. The algorithm developed was verified by analyzing the classical analytical solution of the Stefan problem for the one-dimensional case at a constant advance speed of the phase interface. The value of the verification coefficient was determined from a numerical solution of a nonlinear equation with the use of special built-in Python functions. Substituting the data for the physical model under consideration into the analytical solution and comparing them with the numerical simulation data obtained with the use of the mushy layer method shows that the results are in close agreement, thus demonstrating the correctness of the computer algorithm developed. These studies will allow one to adapt the Python code developed on the basis of the mushy layer method to the calculation of heat storage systems with a solid-liquid phase transition with account for the features of their geometry, the temperature level, and actual boundary conditions.

Development and Prototyping of Jet Systems for Advanced Turbomachinery with Mesh Rotor

This article presents the research results that aim to develop promising mesh turbomachines equipped with jet control systems. The turbomachines operating in difficult conditions in oil and gas production are mainly considered. At the same time, some research results can be used in other production branches, including power engineering and transport. Three-dimensional models for computer simulation of net turbines and jet control systems were developed. Prototypes and micromodels were created to test the performance of mesh turbines and jet control systems using additive technologies. A methodological approach is proposed to create a classification of jet control systems considering their design and technological features. In the course of numerical experiments, the extreme conditions of fluid and gas outflow through a nozzle equipped with a velocity vector control system, in the control range of adjustment of the velocity vector deflection angle from + 90o to -90o within a geometric hemisphere, have been considered for the first time. It was also shown that when using a dual-channel nozzle, there are possibilities to adjust the velocity vector angle (thrust vector) in the range of + 180o to -180owithin the geometric sphere. Compared with the known variants, the control range of the velocity vector angle is increased by nine times. These calculated data are presented in addition to the previously published results of physical laboratory experiments. Preliminary results of numerical experiments show the possibility of creating a new theory in the field of mesh turbines and jet systems. Patents support the novelty of the developed technical solutions. Doi: 10.28991/esj-2021-01311 Full Text: PDF

Frequency selective surface with complex topology elements

Relevance: The solution of specific problems in modern technology of microwave and UHF ranges, such as the implementation of reducing the radar signature of objects, spatial frequency-selective filters, reflectors requires the development and creation of a special class of electrodynamic structures - frequency-selective surfaces. Due to the uniqueness of their electrodynamic characteristics, it is possible to solve quite technically complex problems - suppression of excited surface waves, the creation of "forbidden" zones in the amplitude-frequency characteristics. The purpose of the work is numerical modeling and experimental study of electrodynamic characteristics of plane frequency-selective surfaces with slotted elements of complex topology. Evaluation of the influence of the geometric parameters of the slot inhomogeneity and the material constants of the dielectric substrate on the reflection and transmission coefficients of the frequency-selective surface. Materials and methods: The paper presents the results of numerical simulation of the electrodynamic characteristics of a cell of an infinite 2D frequency-selective surface with the topology of a structural element -shaped and experimental studies of the prototype parameters. Modeling was performed within the framework of the finite element method (FEM) using the ANSOFT HFSS / ANSYS software product. Characteristic measurements are performed in free space by direct measurement of attenuation values. Results: In the course of numerical experiments, it was found that two types of resonances can arise in the structure, associated both with the ratio of the geometric dimensions of the structural element and with the presence of double-sided shielding. The influence of the thickness of the dielectric substrate and the values ​​of the dielectric constant on the reflection and transmission coefficients is investigated. The frequency dependences of the reflection value are established with a change in the spatial orientation of the structure relative to the incident wave front. The dependence of the magnitude of the radio transparency of a two-layer frequency-selective surface on the angle of rotation of the structure around a given axis has been established experimentally. Conclusion: The presented results of numerical simulation of the electrodynamic characteristics of a cell of an infinite 2D frequency-selective surface with the topology of a structural element -shaped and experimental studies have shown the possibility of spatial frequency selection. The totality of the results obtained makes it possible to predict the creation of sufficiently technological and highly efficient frequency-selective surfaces in the microwave range.

Formation of requirements to the laboratory experimental unit under condition of continuation of researches of processes of heat and mass transfer on a model experimental unit

Theoretical results of modeling of vacuum process of evaporation of model liquid in closed volume, carried out for experimental laboratory unit (ELU) and experimental model unit (EMU), differing in size, boundary and initial conditions are considered. The parameters of EMU are determined on the basis of the theory of similarity to the processes taking place in the tank of the launch vehicle stage in the field of small overloads, and the parameters of the ELU selected from the conditions of the existing laboratory equipment. The correlation functions of the process parameters (mass and temperature), showing the degree of proximity of the processes, have been calculated on the example of the process of liquid evaporation under vacuum effects for ELU and EMU, obtained by using the ANSYS Fluent software package. In the course of numerical experiments the vacuum pump capacity was varied to ensure equality of Nusselt criterion for ELU and EMU.

Formation of spatial responses of the optical field in the region of location of the optical antenna array

This article describes a model of an optical antenna array operating in the mode of receiving electromagnetic waves in the frequency range 30-300 THz (in this case, the wavelength varies from 10 ☐ m to 1 ☐m). In the course of numerical experiments (to solve the system of Maxwell equations in the integral formulation, the Weiland method [31] was used) the accuracy of approximation of the spatial structure of the optical field at the points of the “virtual” antenna array elements using the auxiliary field sources method was studied. A study was also carried out on the possibility of using a virtual antenna array formed on the plane of arrangement of elements of a real array to increase the resolution of a multichannel optical system. At the upper frequency of the analyzed range of 300 THz, the wavelength is 1 ☐m. The lattice period was chosen equal to half the minimum wavelength of d=0.5 ☐m, so that it was possible to approximate the spatial distribution of the field in the space between the elements of the antenna array, in accordance with the requirement of the Kotelnikov-Shannon theorem.

ХИМИЧЕСКИЕ ПРЕВРАЩЕНИЯ ВОССТАНОВЛЕННЫХ СОЕДИНЕНИЙ УГЛЕРОДА И ОКСИДОВ АЗОТА В СТЕСНЕННЫХ АЭРОДИНАМИЧЕСКИХ УСЛОВИЯХ ГОРОДСКОЙ АТМОСФЕРЫ

The kinetics of chemical transformations of the most significant pollutants in the cramped aerodynamic conditions of the urban atmosphere is considered, i.e. in the gaps between rows of wide buildings with significant height. High concentrations created in those areas lead to sufficiently high values of reaction rates. The process is described by a stiff system of differential equations, the solution of which is performed by Rosenbrock method. The effect of reduced carbon compounds and nitrogen oxides in a wide range of their concentrations on the rate of formation of a highly toxic secondary pollutant is investigated. In the course of numerical experiments, conditions are determined that correspond to its maximum value. In that case, the transfer of substances from the reaction zone does not have time to occur.

New aspect of drilling development and application in today’s mineral extraction

Introduction. The method of applying the factor of short period delay initiation in rock blasting and its effectiveness can be substantiated by the technical possibility of applying it for both conventional inter-row and current downhole delay intervals. The state of the art in blasting has made it possible to implement the technology of a short period delay. So it is rather relevant and extremely difficult to study of the technology’s aspects in full-scale production conditions. Methodology. This work analyzes the options for rock blasting and blasthole charges designs in order to find out how to implement them in a new and more effective way in modern conditions. A well-known method has been chosen, which combines the rock blasting method and the unconventional design of the blasthole charge. It is used as an example to demonstrate the possibility of expanding the practical range of the selected charge placement schemes. This work has been the first to introduce a hypothesis on the possibility of achieving the same effect in two different designs of blasthole charges, but "acting" in almost the same range of short period delay (SPD) use. The fact is that "vertical" distances between downhole short-delay detonators in a conventional blasthole charge (in this case, a single charge) and "horizontal" distances between parallel converged wells of a beam are almost the same. In this regard, it has become possible to focus not on its "internal" content on the "external" one and explain the features of these mechanisms by means of computer simulation. Due to the apparent specific character of conducting a blast in production conditions and intricate experimental observation, this approach is more realizable in practice and the only possible one. 12 "Izvestiya vysshikh uchebnykh zavedenii. Gornyi zhurnal". No. 6. 2020 ISSN 0536-1028 Results. It is proposed to test various methods of blasting (detonation) based on the idea of replacing (transforming, transferring) the explosion action of detonators ( ≥ 1) in a single well charge (conventionally large diameter) with the detonation of ( ≥ 1) lines of a beam of converged borehole charges of the corresponding small diameter. As soon as the number of beam charge design options increases, the range of research options that can lead to the results with improved quality expands significantly. To achieve this goal, the action of various configurations of charges with in-line short period delay blasting in a beam was studied. It should make it possible to come up to some recommendations for blast control. Summary. On the one hand, the proposed blast patterns show the technological departure from the traditional circular shape of the blast wave, on the other hand, they allow using the effect found in the course of numerical experiment for various purposes, in particular, to ensure blasting effect on (interaction with) design features of various mining methods and production systems in complex geomechanical environment

On Some Features of the Development of Infrastructures in the Polar Regions

The paper describes the possible fact of increased oscillations of the Earth crust in the polar region as compared with the equatorial zone, obtained in the course of numerical experiments, and it has been suggested to conduct a full-scale test experiment. Some basic results of the linear harmonic analysis of simplified finite-element models of the Earth of different scales, which may effect on the design standards of various infrastructures developed in the Arctic region, are given.

Development of models for recognition of technological situations in the operation of electric centrifugal pumps for oil production

The article deals with the problem of constructing models for automation of the technological situations recognition procedure during operation of oil wells. An approach was suggested to recognize technological situations associated with the operation of electrical centrifugal pumping units in oil production. The paper describes the methods for constructing models intended to recognize technological situations characterizing different types of failures of such electric centrifugal pumping (ECP) units. The models based on artificial neural networks, classification trees and support vector machines were considered as separate methods for constructing models for recognizing the technical state of ECP units in oil production. The paper presents the results of studying such methods in the tasks of assessing the technical state of several types of oil and gas production equipment. It is proposed to use sets of models enabling to integrate solutions of individual recognizers to improve situation recognition reliability. In the course of the research, tests were carried out on real operational data of ECP units. The research results showed that the use of such complex models will ensure a sufficiently high accuracy of recognition of technological situations. The proposed complex models provide higher stability of the results, which is confirmed by the results of statistical analysis of solutions obtained in the course of numerical experiments. Thus, it is shown that the proposed complex models for recognition of technological situations are an effective option to be used in object control systems during operation of oil producing wells.

Computation of design parameters influence on air injector fuel atomization

A technique for calculating the two-phase flows at liquid fuel atomization by the air injector is developed. In the course of numerical experiments, the flow parameter distributions over the cross section and volume for different nozzle design options are obtained. The influence of the twist angle of the gas flow on the liquid fuel atomization is analyzed.

The Forecasting of the Single-row Reciprocating Expander Temperature Fields

The single-row reciprocating expander units and elements heat flows and temperature state forecasting results obtained on the basis of the programme KOMDET-M and calculation complex ANSYS are represented in the paper. The single-row expander temperature field dependence on the moving and fixed stage elements design features and materials properties, exhaust chamber and outlet parth geometry, external and internal thermal insulation availability and unit base elements cooling methods was examined in the course of numerical experiment. Isentropic efficiency ηs which maximum level corresponds to the gas final temperature minimum of the stage exhaust chamber Tf is accepted as the perfection criterion of the obtained engineering solutions. The application of the expander stage nonmetallic body having additional internal thermal insulation combined with defining and calculation explanation of optimal volume values, heat exchange surface area, exhaust chamber channels form and section as well as advanced valves and base elements cooling schemes at the design stage was shown to produce a positive effect in low and medium pressure low-consumption expanders at the shaft speed of n ≤ 50 s-1.

Reliability of selected procedures of stress inversion and data separation for inhomogeneous populations of calcite twins and striated faults: insights from numerical experiments

In the course of numerical experiments selected algorithms for stress tensor inversion and separation of heterogeneous populations of calcite twins and striated faults were tested. Artificial data sets were created in a manner simulating natural processes. They were composed of data, dynamically compatible with one or two stress tensors and chaotic “noise” imitating natural imperfections. For calcite twins the classical inversion procedure is considered valid, with restrictions regarding a high proportion of chaotic data, when shape ratio of the stress tensor Φ is poorly constrained. The algorithm of Etchecopar (1984 fide Tourneret and Laurent in Tectonophysics 180:287–302, 1990) devised originally for calcite twins has been modified and applied to fault/slip data, facilitating a rejection of incompatible outliers. Two main classes of data separation procedures were tested: separation contemporary with inversion and separation prior to inversion, utilising hierarchical clustering. The separation contemporary with inversion performs moderately but often fails with complex calcite twin sets. The performance of hierarchical clustering is high, but only with a σ 1 orientation as a similarity criterion—the new strategy introduced in this contribution. For fault/slip data the hierarchical clustering with the right-dihedra construction as the similarity criterion (Nemcok et al. 1999) is satisfactory. Additionally, a new approach is proposed for fault/slip data, utilising principles of the classical algorithm for heterogeneous populations of calcite twins. Validated algorithms for striated faults were successfully applied to a natural data set from the Holy Cross Mts (central Poland).

The numerical modelling of long wave propagation in the framework of non-linear dispersion models

The work is devoted to the questions of numerical modelling of long wave propagation, in particular tsunami waves, in the framework of non-linear dispersion models of the Boussinesq and Korteweg-de Vries type. The first part of the work includes a classification of some known mathematical models, in terms of dispersion correlation, phase and group velocities. Problems arising on the construction of finite-difference approximations of non-linear dispersion models are discussed in the second part of the work, special attention is given to the questions of constructing discrete boundary conditions. In the conclusion the results obtained in the course of numerical experiments and estimation of specifics of finite-difference models, and the contribution of non-linear dispersion effects in the process of wave propagation in the coastal zone, are discussed. The results of calculations of tsunami wave propagation in a wave tube with real bathymetry, are given.