Physical Modeling of the Electrophysical Processes of the Formation of the Corona During the Operation of Electric Power Facilities

One of the priority areas of research in the field of energy-efficient heat supply of premises is the search for alternative solutions for the efficient generation of thermal energy. The priority of this area is growing every year, although there are very few actually applicable system solutions developed. The most universal solution among devices with alternative heat energy generation is an air source heat pump (ASHP). To improve the efficiency of heat pump and heat exchange systems in the climatic conditions of the continental climate, domestic scientists have developed technical and organizational-technological solutions that have received positive results in the context of practical implementation at real construction sites. Nevertheless, for the further development of devices today there are opportunities for rational modernization of classical solutions for heat supply of buildings. One of the unsolved problems is the lack of physical and mathematical models of non-stationary heat transfer processes in the internal circuit of the ASHP, complicated by the phenomena of phase transformations during boiling and condensation of the refrigerant inside the system, and desublimation of moisture on the outer surface of the heat exchanger fins. Existing thermodynamic calculation methods offer only recommendations for the conditions of application of heat pump systems based on laboratory studies and tables. The situation can change dramatically with the availability of adequate physical and mathematical models of processes that allow analyzing the state of the working fluid in the ASHP circuit under conditions of pronounced non-stationarity of hydrodynamic and heat exchange processes.

The article discusses the features and results of physical and mathematical modeling of filtration experiments on terrigenous and carbonate rock core samples at different crimping pressures. Such studies are necessary to understand the effect of rock pressure on the reservoir properties and relative phase permeability (RP) of reservoir rocks, including from the standpoint of the Digital Core technology, since core tomography is usually performed under atmospheric conditions and data on rock properties are required for reservoir conditions. The article discusses the features and results of physical and mathematical modeling of filtration experiments on terrigenous and carbonate rock core samples at different crimping pressures. Such studies are necessary to understand the effect of rock pressure on the reservoir properties and relative phase permeability (RP) of reservoir rocks, including from the standpoint of the Digital Core technology, since core tomography is usually performed under atmospheric conditions and data on rock properties are required for reservoir conditions. The laboratory study of the relative permeability was carried out on composite core models by the method of stationary filtration at crimping pressures of 10 and 20 MPa. Mathematical modeling of filtration experiments was performed in the Eclipse simulator. The distribution of porosity in the hydrodynamic models of the core was set based on data from computed tomography of the core. The distribution of other rock properties (permeability, residual saturations, RPP values at residual saturations) was calculated using generalized dependencies. It is shown that for terrigenous and carbonate rocks, an increase in pressure leads to different behavior of the RPP functions and fluid mobility. The results of laboratory studies are interpreted from the point of view of processes at the micro level, based on the formation of the nature of the flow and the associated water saturation during deformation of the void space. It is also shown that filtration experiments on core at different rock pressures can be simulated on a hydrodynamic simulator, but at the same time, the study of patterns in the change in model parameters with a change in pressure depends on the presence of patterns in the behavior of rock properties based on the results of physical modeling.

Platform structures are commonly utilized for various purposes including offshore drilling, processing, and support of offshore operations. A jacket is a supporting structure for deck facilities, stabilized by piles driven through it to the seabed. In a jacket design, operational and environmental loads are very important and must be intensively investigated to secure the stability of structures during their service life, as well as installation phase. The main purpose of this research is to evaluate the results of physical modeling for the launch operation of jackets from barge into the sea, as the most hazardous stage in the installation of a platform, and compare them to those of numerical modeling. Both physical and numerical modeling parameters are described and they are examined on a prototype platform, i.e., Balal oil field production and living quarter platform that is a 1700 tone, eight-legged jacket located in the center of Persian Gulf, some 100km distance from Iranian Lavan Island. It is found that both numerical and physical methods can describe the motion of the barge similarly well, but some differences are traced in the motion of jacket. The inequalities are, then, appeared to be due to the Froude-type parameters applied for modeling purpose. One notable fact investigated in this research is the necessity for choosing Reynolds–Froude type in the physical modeling of the launch, instead of Froude type. This is because, in addition to the importance of gravitational and inertial forces, the viscosity affects the drag hydrodynamic force, as well. It should be noted that viscosity and consequently drag coefficient in Froude type modeling cannot be quite applicable and this causes the difference observed between the results of physical and numerical modeling. Although there have been so many jacket launching designed and probably their physical models have been tested, but to the best of our knowledge from the literature, there was found no study on Reynolds–Froude physical modeling of jacket launch phenomenon. If one is interested in practicing a Reynolds-Froude physical modeling, it could be done either in a centrifuge test or by using a fluid with lower viscosity dependent on the scale of model, or even by finding a fluid (with new viscosity and new density) and a new gravity to have simultaneously the Froude and the Reynolds similarity laws satisfied.

The results of mathematical and physical modeling of global and local hydrological processes in the water area are presented. By the method of mathematical modeling revealed variability of large-scale circulatory flow and mass transfer in a water-restricted area with complex obstacles.In laboratory conditions, by experimental methods, in the hydrodynamic tray, on the channel and the laboratory stand, detected of local hydrodynamic processes and mass transfer around local obstacles - three-row fuel burner rafts. Mechanisms of formation of erosion and transfer of the soil near and within the single and group structures of the grillages located on the laundering sandy bottom of the channel are revealed.

One of the most promising methods for manufacture of axially symmetric parts such as disks or hollow shafts of gas turbine engines is local deformation using cold rolling. Physical and mathematical modeling can be quite effective for designing this class of equipment and process operations. This article presents the methodology and results of physical and mathematical finite element modeling of local deformation of parts such as a tapered cylinder fabricated from chromium steel alloy grade 11H11N2V2МF-Sh. Chemical elements in the alloy are designated by the letters which stand for: H – Chromium, N – Nickel, V – tungsten, M – molybdenum, F – vanadium, Sh – electroslag remelting. According to GOST 5632-72 (Russian standard), this type of nickel-chromium alloy consists of about 11 % of chromium, 1.5–2 % of tungsten and nickel, up to 1 % of molybdenum and vanadium, and 0.11 % of carbon, hundredths of one percent of phosphorus and sulfur. It is heat-resistant high-grade steel, which is used for the manufacture of parts operating unloaded at 900–1000 °C. The purpose of the paper is to analyze the process energy-power parameters and possible fracture of parts during deformation.

Nowadays, Russia has the longest heating network system in Europe (about 125 000 km in total). Given the constant growth in the volume of construction space, the length will constantly increase. Consequently, there is a request to increase the level of reliability of heat supply networks. It is possible to satisfy the request only by increasing the volume and quality of comprehensive diagnostics of heat supply networks with simultaneous reduction of time costs. This is possible only if a new generation of measurement and computing complex (MCC) is developed for the diagnosis of heat supply networks. The team of authors examines the features of the information environment in heat supply networks, separately noting the possibility of switching the flow from single-phase to multi-phase and back. The paper proposes to consider a solution to a problem that arises when trying to visualize physical and mathematical models of thermodynamic processes of single-phase flows using MATLAB. It consists in the fact that the desired physical and mathematical model should describe the thermodynamic processes of a single-phase flow, but taking into account that this flow moves in the external heat supply network. The possibility of using the MATLAB functional environment for developing a model based on visually oriented programming is considered in detail, which allows us to lay the foundations for further forecasting the development of the heat supply system.

Purpose. When solving practical problems that require the creation and further analysis of the model, an important criterion is the labour intensity of modeling. In this regard, the article is aimed at formalizing the modeling process and using the method of step-by-step modeling for the design of technological processes. This approach allows you to design processes and tasks according to the following stages: physical modeling, mathematical modeling, discrete computer modeling and simulation. Methodology. To solve the problem, a methodology of step-by-step modeling is used. The simulation involves 3 stages and uses the decomposition algorithm, i. e. considers the problem from global to detailed. At the first stage of this implementation, the necessary information is collected for the experiment. This information is presented in the form of statistics. In the second stage, further processing takes place, which is performed by checking the compliance of the input data and the process with the question of how this process should be performed. The last stage is the simulation of passages of this fragment, which is represented by a chain of transitions, obtaining statistics of time efficiency of this process, weaknesses of the process and the ability to compare the results obtained during modeling and in the real process, as well as the ability to predict future results and actions. Findings. The technique can be used to study complex technological processes in the enterprise. It allows modeling of complex processes to obtain information about the time efficiency of the technological operation, finding weaknesses in it and patterns in the occurrence of random events that may affect the operation. Using this approach can be very effective in the systems that require constant real-time monitoring, as this tool can be modified by adding sensor kits that will constantly send information to the system or equip an additional system that will provide ready-made information packets. Originality. The method of step-by-step modeling of representation has been improved, which consists in the simultaneous use of physical, mathematical and simulation modeling of complex processes with a set of stages of their implementation. Practical value. The proposed technique is designed for step-by-step modeling of the technological process with the subsequent construction of simulation programming.

Quality and operational properties of rails determine duration of their operational service. The main parameters that determine quality of steel are chemical heterogeneity and presence of non-metallic inclusions in metal. Efficiency of homogenization of metal melt and its refining from non-metallic inclusions in tundish is largely determined by organization of hydrodynamic processes, internal geometry of ladle, and presence of additional refractory elements. Using physical and mathematical modeling, study of the influence of additional refractory elements of various configurations of intermediate ladle on processes of melt flow was carried out. Physical modeling of hydrodynamic processes in the tundish taking into account requirements of similarity theory was made on specially created laboratory-experimental complex. Numerical experiments were carried out using computational fluid dynamics methods (finite volumes) on three-dimensional turbulent mathematical model with a singlephase representation of metal melt flow in tundish. To evaluate efficiency of melt homogenization according to results of physical and mathematical modeling, new technique has been developed based on analysis of distribution of time of liquid placement in continuous flow reactor. According to the results of experiments, configuration of the internal volume of tundish of four-strand CCM is proposed. A construction is considered that provides effective homogenization of molten rail steel and its refining from non-metallic inclusions. The design of full-profile compartments was developed and tested under industrial conditions, which ensure rational organization of melt flows, its homogenization and efficient refining of rail steel from non-metallic inclusions in the tundish. Industrial research was carried out under the conditions of four-strand CCM No. 1 of EAF shop at JSC “EVRAZ ZSMK”.

The Zuppinger water wheel, developed in the 1850s, is one of the most efficient water wheels and is commonly used for low-head hydropower generation. The high efficiencies of the wheel over a wide operating range, its simplicity in design and slow rotational speed offer a low-cost and environmentally friendly low-head hydropower solution. A physical and numerical model study of a wheel is presented in this paper. Three-dimensional numerical simulations were performed using the computational fluid dynamics (CFD) code Flow-3D. The influence of grid size on the results of the numerical model was assessed using a systematic grid refinement study. Grid convergence indices (GCIs) were calculated for two grid sets each, with three different grid sizes, using a constant grid refinement ratio. The GCIs were reduced to levels below 5% for the selected quantities of interest. The CFD model results were compared with physical model results at different operating points of the wheel. The maximum differences in power output and efficiency between the physical and numerical model results were 2.5% and 8%, respectively.

Introduction (problem statement and relevance). The article describes a physical model of a road train with active drive of semi-trailer wheels. The results of research tests of the physical model are given, with the help of which the adequacy of the mathematical models of dynamics of the road train as a part of a truck tractor and semi-trailer with active wheel drive is evaluated. The purpose of the study is estimation of efficiency of the technical solutions aimed at increase of vehicle passability and maneuverability.Methodology and research methods. In the course of the study the method of analysis of results of tests of the operating active road train scaled mock-up, the method of comparative analysis of the results of mathematical and physical modelling have been used. Scientific novelty and results. The performed studies confirmed correlation of the physical and mathematical modelling results, as well as indicated that the use of physical modelling serves as an efficient method to obtain an objective assessment of operational properties of the designed road train. The article considers constraints and limitations of using a scalable vehicle to study its dynamics. Matters of model parameters validity, conditions for dynamic similarity, and physical modelling results for active road train dynamics are given.Practical significance. Physical modelling of a (full-)scale sample using a scaled model reduces the costs and time when developing an active road train with new technical solutions, and increases reliability of the results obtained through the mathematical and physical modelling.

Unlike the materials widely represented in domestic and foreign scientific, technical and reference literature, the article theoretically substantiates the need to take into account in laboratory and bench tests of mechanical systems with friction units the presence and interconnection of dynamic processes occurring in a frictional contact and in a mechanical quasilinear subsystem; ensure identical: parameters of macro- and micro-roughness of contacting surfaces, frequencies and forms of natural vibrations, physical and mechanical properties of tribocontacts, as well as dynamic (integral) characteristics of a natural object and its physical model. The article presents the methods of physical and mathematical modeling and tribospectral identification of friction processes. The features of these methods and an example of dynamic monitoring of a mobile mechanical system using the example of a friction system: “way - rolling stock” are consideredThe first section in your paper.

Problems of the physical and mathematical modeling of processes that occur in additive technologies of the three-dimensional laser manufacturing and prototyping of metal items with complex geometry are discussed. Results from numerical modeling of the processes that occur upon coaxial laser cladding and the selective laser melting of powders are presented.

This work defines general methodological approaches to the analysis of interrelated physical and mechanical processes and states in the elements of radial-piston hydraulic transmissions. The key characteristics of these approaches are, firstly, a generalized parametric description of various processes and states in hydraulic transmissions, and secondly, the construction of integrated modeling problems of these interconnected physical processes. Such integration differs from the traditional approach, which involves the sequential solution of separate independent problems, which allows to create more corresponding mathematical models of work processes in hydraulic transmissions and to substantiate progressive technical solutions. In particular, there were a number of processes and states considered in the complex and interaction. Special attention is devoted to the kinematics and dynamics of movement of hydraulic transmission elements. Also important is the analysis of contact interaction and the stress-strain state of hydraulic transmission elements. Among the determinant one’s – the processes of hydrodynamics of the working fluid in the working volumes of hydraulic transmissions. In the general description of the mathematical models of the processes and states under study in hydraulic transmissions, the main state variables and factors were determined, which serve as the basis for the forming of more detailed models within the framework of further research. The key dimensions, that used in the calculation models of processes and states in hydraulic transmissions were evaluated, which makes it possible to classify them according to the degree of significance. It has been established that neglecting individual stages of the research can lead to significant errors in the calculation results compared to the behavior of real objects. Thus, the developed comprehensive model of processes and states in the elements of radial-piston transmissions, on the one hand, is sufficiently complete, as it encompasses all significant aspects of the functioning of these transmissions. On the other hand, it is impractical to remove individual parts from it. Therefore, the applied approach made it possible to build a basic mathematical model of processes and states, balanced by the criteria of adequacy and complexity.

The monograph summarizes the results of mathematical and physical modeling of mechanical processes in the production of crystalline materials using a number of technologically significant industrial processes (growth of technically valuable single crystals from melt for microelectronics and from salt solutions for photonics, thermal pressing, and crystallization from powders for thermoelectric materials). Data are presented on the effect of the main control actions on the hydromechanics of liquid phase (melt and salt solution), including control of the rotation of the crystal, the crucible, and various mixer types, sectional thermal heating of the crucible walls, complex crystallizer designs, the use of magnetic fields, and microgravity conditions. Approaches are discussed that ensure the optimization of hot zone design and process parameters and control of heat and mass transfer processes in the liquid and solid phases, including control of the stress state and defect formation processes in the solid phase. Software packages for mathematical modeling, including those with the possibility of remote operation, are discussed. The monograph is intended for specialists in the field of crystalline materials technologies, mechanics, thermal physics, as well as for postgraduate students and students of relevant specialties.

Statistical analysis of bimslope stability using physical and numerical models