Results Of Numerical Modeling Research Articles

Creation and research of numerical models of cyclones with inclined and horizontal inlets

The article considers the challenges of using cyclone devices for cleaning gas emissions from solid fuel combustion in power engineering and industry. With the increasing energy consumption and generation, including the use of coal, the requirements for the efficiency of cleaning emissions from small solid particles of classes PM10 and PM2.5 are also rising. One of the key tasks is to maintain high cleaning efficiency while minimizing energy costs, which is also important for reducing the environmental impact of generation and industrial production. The article considers the design features of currently used cyclones, as well as existing approaches to their classification. The main focus is on modern areas of research related to numerical modeling based on CFD (Computational fluid dynamics) aimed at optimizing the design of separators. It is shown that most studies are carried out for cyclone operating conditions in production cycles, rather than in emission cleaning systems that operate at low suspended matter loads. Using the example of creating numerical models of cyclones with inclined and horizontal inlet pipes (CN-11, SK-CN-34), the article discusses certain features of geometry creation in the SpaceClaim Direct Modeler (SCDM) environment, which ensure the correctness of grid generation and calculations in the future. The results of numerical modeling carried out using the ANSYS Fluent software are presented. The turbulence model (RANS, Reynolds Averaged Navier – Stokes), methods for closing the Navier – Stokes equations (k-ε model with near-wall functions), and methods for calculating the dispersed part of the flow (Euler – Lagrange, DPM) are selected based on the conditions relevant to the systems for cleaning emissions from coal generation. The results indicate that, with the same pressure drop, the efficiency of settling suspended matter with a concentration of 100 mg/m3 or less in an apparatus with an inlet angle of 11° to the horizontal can be higher than that of a cyclone with a horizontal inlet.

Influence of Horizontal Distance Between Earthmoving Vehicle Load and Deep Excavation on Support Structure Response

The objective of this paper is to investigate the influence of earthmoving vehicle load position on the deformation and internal force characteristics of a deep excavation (DE) support structure. The position of the earthmoving vehicle load near a DE is described by the horizontal distance between the earthmoving vehicle load and the DE. A two-dimensional finite element model is established for simulating DE engineering under the earthmoving vehicle load. The load of the earthmoving vehicle is treated as the static load, and the influence of the earthmoving vehicle load on the excavation support structure is considered from the static point of view. The numerical results of the finite element model agree well with the measured data from the field, which verifies the validity of the model. On the basis of this model, multiple models are established by changing the horizontal distance (D) between the earthmoving vehicle and the DE. The influence of D on the support structure and its critical magnitude for ensuring safety were studied. The results show that the underground diaphragm wall (UDW) is the main component for which horizontal displacement occurs under the earthmoving vehicle load. The horizontal displacements of the support structure exhibit an asymmetric distribution. When D decreases from 20 m to 0.5 m, the horizontal displacement of the UDW near the loading side increases, and the maximum horizontal displacement occurs at the top of the excavation support structure. The critical magnitude of D for ensuring safety is found to be 1 m. When D is less than 1 m, the DE is in an unsafe state. The UDW is the main component subject to the bending component. The bending moment distribution exhibits an “S” shape. The maximum bending moment increases with the decrease in D, and it occurs at the intersection of the second support and the UDW. As D decreases, the axial force in the first internal support changes from pressure to tension. The axial forces in the second and third internal supports are both pressures. The axial force in the third internal support is the largest. The research results have a positive effect on the design and optimization of DE support structures under the earthmoving vehicle load.

Membrane piezoelectric MDS-actuator with a flat double spiral of interacting electrodes

A schematic diagram and mathematical model of functioning of a new piezoelectric membrane (MDS) actuator with double spiral (DS) electrodes on the upper and/or lower surfaces of a thin piezoelectric layer with axisymmetric and periodic (with a small period) in radial coordinate mutual reversed electric polarization are presented. The polarization of the layer was realized as a result of connecting the polarizing electric voltage of the appropriate value to the outputs of the double spirals of the electrodes. The electrodes of each (upper and lower) double spiral of the MDS-actuator are made in the form of electrodeposited ribbon coatings on the surfaces of the piezoelectric layer in close proximity to each other (due to the small spiral pitch) to create high values of electric field strength along the lines of force in localized areas of the piezoelectric layer between them when an alternating or constant control electric voltage is connected to the electrodes, in particular, with positive and negative values of the electrical potentials. Importantly, the electric field force lines and, as a consequence, the polarization of the piezoelectric layer of the MDS actuator are oriented mainly along (i.e. towards or against) the radial coordinate of the membrane, in contrast to many conventional actuator schemes. The results of numerical modeling for a circular elastic membrane with piezoelectric actuators installed on its upper and lower surfaces confirmed the effectiveness of the proposed piezoelectric MDS-actuator when it functions according to the “bimorph” scheme, including the use of the proposed new structural element (section) – a piezoelectric “compression ring” MDS at various geometric and control parameters. The effect of a significant increase in the membrane deflection with installed piezoelectric MDS-actuators compared to the use of traditional homogeneous plate piezoelectric actuators of bimorph type for different conditions of the membrane fixation, in particular, stationary (rigid) fixation of its center is revealed. For a hybrid piezoelectric MDS-actuator including independent concentric round and circular (i.e. “compression ring”) sections, the non-monotonic nature and numerical analysis of the nonlinear dependence of the largest deflection at the center of a hinge-immobile membrane fixed at the edge on the ratio of the radii of its round and circular MDS sections were revealed. The cases in which the effect of the “compression ring” is manifested, i.e. when the maximum deflection of a membrane with the “compression ring” exceeds the best possible value of the deflection of this membrane without its use in the traditional “bimorph” scheme, are identified. The new piezoelectric MDS-actuator can be used in micromechanics, controlled optics, sensor technology, acoustics, in particular, in the manufacture of piezoelectric acoustic or sensor elements of membrane type, electromechanical transducers for vibration energy collection.

Linear transverse flux generator for wave energy conversion: design optimization and analysis

Abstract The electric power industry impacts each state’s economy significantly, driven by increasing electricity consumption that necessitates expanding power plants and finding alternative energy sources. Among alternative energy sources, ocean and sea wave energy converters can be distinguished as a separate class. Wave energy converters transform wave energy into mechanical and then electrical energy. The purpose of the study is to analyze and optimize the magnetic system of a transverse flux machine (TFM) linear generator and to determine the influence of the distance between the stator cores on the efficiency of the generator. This research included conducting 3D modeling and analysis to identify this rational distance. The methods for investigating the magnetic system and calculating the magnetic field pattern are divided into analytical and numerical. Thanks to advanced software for solving such tasks, numerical calculation methods based on the finite element method play a decisive role. Meanwhile, analytical calculations of the magnetic circuit are performed using Kirchhoff’s second law for preliminary analysis. The article discusses a two-phase linear TFM generator with a U-shaped core and permanent magnets. The results of numerical modeling show that the distance between the stator cores should have a specific size and requires detailed selection when designing the magnetic system in each particular case. In the design studied, it was calculated that 6 mm between the stator cores increases the machine’s performance. 3D modeling is necessary for accurate analysis, considering the axial magnetic flux to minimize stray fields and their mutual demagnetization. Future research will explore an E-shaped core TFM design.

Peculiarities of flexural wave propagation in a notched bar

The results of numerical modeling and experimental studies of the propagation of flexural elastic waves in a metal notched bar approximates the effect of an acoustic black hole are presented. The sample is a bar with notches, the depth of which increases according to the power law with an exponent equal to (4/3). It has been confirmed experimentally and with the simulation results, that such bars slow down the propagation of an elastic wave to the end of the bar. It is shown in such structures flexural waves have dispersion and their localization at the end of the bar is higher for some natural frequencies than that of a solid rod. The natural oscillations of the whole and notched bars are compared, i.e. the shape of the amplitude of the flexural wave along the rods. The dependence of the flexural wave length in a notched bar on the frequency is investigated as a wave propagates to the end of the bar.

Phase synthesis method in multi-aperture optical systems based on iterative image processing algorithms

Background. Modern technologies in the field of optics and photonics place high demands on the quality and output power of the radiation source. The fulfillment of these requirements can currently be achieved by creating multi-aperture laser systems with coherent beam addition. The main problem of creating such systems is the development of phase synthesis methods in a multichannel optical system. Aim. In this paper, we consider a phase synchronization method without a reference beam for a coherent addition system with active feedback, which is based on the Gerchberg–Saxton algorithm. This algorithm makes it possible to reconstruct complex field amplitudes in the aperture and focal planes from intensity distributions in these fields. The application of this algorithm for multichannel systems is analyzed and its features, such as the occurrence of stagnation and ambiguity of the solution, are revealed. Methods. Solutions are proposed to eliminate the problem of convergence of the algorithm to side solutions and getting the iterative procedure into the local extremum using global optimization algorithms, methods of reducing the dimension of the problem and the introduction of antisymmetric amplitude modulation. Results. The paper demonstrates the results of phase field reconstruction for a large number of optical sources. For a seven-aperture system, a physical simulation was performed to restore phase information, confirming the results of numerical modeling. Conclusion. The proposed approach is a reasonable alternative to currently existing methods and can be used in the problem of coherent addition in multichannel optical systems.

Безплазовий метод конструкторської підготовки виробництва літаків авіації загального призначення

The article’s subject is the design preparation for producing light general aviation aircraft. This article aims to develop design solutions for a light cheap aircraft with low flight and ground costs, to substantiate the possibility and necessity of using modern CAD systems and new plazless methods to ensure the interchangeability of light aircraft components to reduce design and production costs. Objective: to analyze the global demand for light aircraft, to substantiate the possibility and feasibility of introducing independent (plazless) methods for linking technological equipment and aircraft design components, to develop a list of design work and expected results, to develop digital models (electronic drawings) of the aircraft as a whole and its components, to prove the effectiveness of such approaches. The research methods used are the analysis of scientific and technical documentation, numerical modeling of the aerodynamic flow around the aircraft, the stress-strain state of the units, and the design of the aircraft and its components considering the results of numerical modeling. The following results were obtained: a set of digital models (electronic drawings) of the whole aircraft, a fuselage, a wing, a horizontal and vertical tail, a chassis, digital models (electronic drawings) of the aircraft parts. The scientific and practical novelty of the obtained results is as follows: a set of aircraft design engineering documents developed based on statistical data analysis and numerical modeling will allow manufacturing, testing the aircraft, and obtaining a certificate of airworthiness, which, in turn, will make it possible to subsequently begin serial production of the aircraft and create full-fledged primary flight training classes designed to improve flight training activities for cadets of higher military educational institutions and create opportunities for training civilian pilots.

Effect of the Effective Metal Surface Area of Two Different Flow Diverter Stents on the Stagnation Region Formation Inside the Aneurysm Sac

Abstract Objective Flow diversion (FD) is a relatively new technique for treating large, wide-necked, or fusiform aneurysms. Although FD is a more preferred option than coiling or clipping techniques in neurosurgery and neuroradiology clinics, the blood flow mechanism inside the aneurysm sac is not fully understood after the treatment. Besides, effective metal surface area (EMSA), a property of an FD related to porosity, shows variation at the patient's aneurysm neck by providing more or less blood flow inside an aneurysm sac than planned, causing nonstagnant or stagnant fluid region formation in the sac, respectively. Thus, the change in FD's EMSA can significantly affect the treatment's effectiveness, making even operation unsuccessful when variation in FD's EMSA at the aneurysm neck is overlooked. Materials and Methods In this study, a large aneurysm of a 52-year-old female patient was numerically investigated by virtually placing two commercially available FDs with different EMSA values one by one into the aneurysm-carrying artery. Results While FD stents at the aneurysm site substantially reduced the blood flow into the aneurysm, an FD with a 15.6% EMSA caused blood to flow in the aneurysm sac to have six times more kinetic energy than that of FD with a 29.5% EMSA. Conclusion Although FD's EMSA value demonstrated nearly up to 20% reduction at the patient's aneurysm neck based on a product catalog value, numerical model results revealed that the stagnated region's formation inside the aneurysm sac could be determined within a 9% difference based on digital subtraction angiography reformat image.

Simulation of resonant liquid sloshing in a tank with vertical baffles

The material presents the results of numerical modeling of internal fluid flows geometry in tanks that are subject to fluctuations due to external force influences. Similar applied problems occur when transporting large volumes of liquid, for example, in tanker ships. Given the rather significant moving masses within the reservoirs (tanks), as a rule, there are shock pressures on the walls and internal structures of the guiding devices, which can cause their deformation and even destruction, which leads to serious emergency situations.Numerous studies devoted to the determination of the force effects of liquid flows on the walls of tanks came to the conclusion that the presented phenomena are of a strongly nonlinear nature, depend not only on the amount of liquid and the directions of its movement within the tank, but also on the formation of velocity and pressure fields over time. The specified parameters are decisive in predicting possible resonance phenomena in tanks, which in turn can become the main factor in the design of means of damping or control of inertial fluid flows.The proposed work is devoted to the mathematical modeling of the mentioned phenomena in tanks, as well as the analysis of the force effect of internal inertial flows, which cause the occurrence of shock pressures on internal structures. On the basis of the indicated research results, it is possible to propose rational from the point of view of damping the design of guide devices in the form of flat rigid baffles.

Stationary regimes and parametrization of ekman friction in the Karman model of flow induced by external vortical body force

The detailed study of stationary regimes of Karman axisimmetric flow induced by external vortical body force is done. It is extracted two stationary regimes – with small (Batchelor regime) and with substantial (Stewartson regime) secondary circulation. The diagram of regimes existence is plotted in the space of flow parameters – Rossby and small Ekman numbers. For the flow decaying to the stationary flow in the Batchelor regime a theoretical model is proposed with which it was possible to derive a parametrization of linear friction coefficient, Ekman pumping velocity, stationary pressure from mean flow characterictics (vorticity and divergence). In the Stewartson regime a parameterization of the stationary flow is proposed and also numerically studied a decay rate. It is shown a good agreement between theoretical and numerical model results.

Dynamics of the plasma ejection structure in laboratory modeling of young star jets at plasma focus facilities

The use of “plasma focus” type facilities, such as PF-3 (Kurchatov Institute), makes it possible to carry out well-controlled and diagnosable laboratory experiments to study laboratory jets with scale parameters close to the jets of young stars. In this paper, we present the results of numerical modeling of plasma outburst propagation in PF-3. A self-consistent configuration was chosen as the initial conditions, which correctly takes into account the internal structure of the jet. This allowed us to obtain a detailed structure of the interaction between the magnetized emission and the ambient gas. Due to the scalability of such a structure, one should expect such a structure from the head shock waves of jets of young stars.

Assessment of Tsunami Hazard for the Coast of Oktyabrsky Spit, Western Kamchatka Based on Results of Numerical Modeling

Assessment of Tsunami Hazard for the Coast of Oktyabrsky Spit, Western Kamchatka Based on Results of Numerical Modeling

Shape of fragments cloud behind heterogeneous screen by a space debris particle impact

Technogenic pollution of near-Earth space poses a threat to the functioning of spacecraft. Collisions between space debris (SD) and spacecraft (SC) structures can have catastrophic consequences or cause localized damage, leading to the loss of SC operability or the failure of certain functions. The SC body must effectively protect the internal equipment from various external impacts, be technologically feasible to manufacture, and have as little mass as possible. As a result, the task of designing spacecraft bodies and protective screens for low-orbit SC is particularly relevant due to the large concentration of SD in low Earth orbits.A comparative numerical study was conducted to evaluate the effectiveness of various thin shields in protecting against impacts from space debris particles. The study examined homogeneous shields made of A356 aluminum alloy and 316L stainless steel, as well as volumetrically reinforced composite shields produced using additive manufacturing with steel inclusions, and shields with a gradient distribution of steel throughout the thickness of an aluminum matrix, all with the same areal density. In all the heterogeneous plates considered, the volumetric concentration of steel was 36 %. The study covered an interaction velocity range of 2–9 km/s. Numerical modeling results indicated that the structure of the thin heterogeneous plate does not affect the shape of the debris cloud formed behind the protective shield. The findings of this study can serve as a basis for selecting materials for the development of more effective protection for spacecraft against high-velocity impacts.

A New Methodology for Quantitative Risk Assessment of CO2 Leakage in CCS Projects

Summary Assessing risks during carbon dioxide (CO2) sequestration involves a systematic process to identify them (risk assessment), analyze, prioritize, score them (risk analysis), develop mitigation strategies, and plan for measurement, monitoring, and verification (MMV) activities. In this context, risk assessment and analysis are often conducted involving qualitative approaches and/or subjective evaluations based on experts judgments. In this paper, we propose to use numerical results of dynamic subsurface modeling to assess risks in a more precise, less subjective, and quantitative manner, enabling a comprehensive definition of effective MMV plans. In this context, MMV evolves into modeling, measurements, monitoring, and verification [(M)MMV]. The conceptual model used for this study integrates flow and geomechanical-coupled behavior to assess caprock integrity, faults reactivation, and ultimately the risk of CO2 leakage. Uncertainty analysis and a 4D probabilistic workflow are used to quantify the likelihood and consequences of CO2 leakage and to score risks. The proposed approach offers a general framework to enable subsurface-modeling-based quantitative risk assessment (QRA) for the definition of successful (M)MMV plans. In this study, we have focused on the QRA of leakage risks through the fault and intact caprock. Other applications are possible, such as: (1) leakage risks through the caprock resulting from caprock failure; (2) lateral CO2 migration leading to permit limits violation or inducing interferences with neighboring activities; (3) leakage risks resulting from loss of well integrity; (4) risks of faults reactivation; (5) risks of surface heave; and (6) risks of induced seismicity. All these results can be used to formulate effective (M)MMV strategies for an optimized and cost-effective risk mitigation.

Multiprobe Planar Near-field Range Antenna Measurement System with Improved Performance

This article presents a novel multiprobe planar near-field range (PNFR) measurement system. The said system simplifies the overall mechanical design, making it simpler than the existing scanning probe PNFR measurements, and also significantly reduces testing time. A dielectric-based probe is introduced to reduce the antenna size, thereby improving resolution. The probe under consideration is an antipodal Vivaldi antenna offering broadband support and ensuring wideband characteristics of aerials. Numerical results for representative X-band antenna models, presented in the Matlab environment, demonstrate robust performance of the developed measurement system.

Measurement of pulse current during high voltage tests using Rogowski coil with non-inverting integrator

The work is devoted to the development and modelling of the system of pulse current measurement during high-voltage tests and experiments. The proposed measurement system is based on the application of Rogowski coil with non-inverting integrator. The results of numerical modelling of the developed current measurement system are compared with the results of application of a low-inductance shunt resistor, Rogowski coil with passive RC-integrator and Rogowski coil with inverting active integrator in similar measurement systems. Various standard pulse currents including steep edge pulse (1/20 µs), large amplitude current pulse (4/10 µs), lightning pulse current (8/20 µs), switching pulse current (30/80 µs), and 1-3 ms pulse currents are modelled for the comparative test. From the simulation results, it follows that the developed Rogowski coil with the proposed non-inverting integrator has sufficiently high accuracy in a wide frequency band overlapping the frequency band of standard pulse currents in high-voltage tests.

Three-dimensional numerical simulation and experimental validation of airborne ground-penetrating radar based on CNCS-FDTD method under undulating terrain conditions

Traditional Finite Difference Time Domain (FDTD) approaches face challenges with increased computational demands and errors as terrain complexity and flight altitude rising. This study introduces the Crank-Nicolson-Cycle-Sweep-FDTD (CNCS-FDTD) method, enhancing airborne ground penetrating radar (GPR) simulations over undulating terrains. CNCS-FDTD, as an unconditionally stable implicit algorithm, overcomes these by allowing larger time steps without the constraints of the Courant-Friedrichs-Lewy (CFL) condition. Our research aims to assess how CNCS-FDTD can improve computational efficiency and accuracy in modeling airborne GPR responses across varied terrains. Initial simulations using a three-dimensional graben model indicate that CNCS-FDTD can maintain calculation stability with significantly larger time steps, reducing computational time by 42%. To further verify the reliability of the numerical simulation results, the paper also presents experimental tests of the undulating terrain model. By comparing the numerical and physical simulation results of models under different flight altitudes and terrain conditions, the accuracy of the simulation results is validated.

Dynamic Characteristics of a 1950s Heritage Building: A Comparison of Original Design Methods and Modern Techniques

Research on design rules and methods for architectural heritage is an important aspect of conservation practice. Nevertheless, efforts to recover and divulge design methods for Modern Heritage remain limited. This paper is related to the recent structural assessment of a 15-storey heritage building built in 1950, during which a document describing the original seismic analysis of this structure was identified. The methodology employed is of particular interest, as it involves the application of pioneer concepts of dynamic analysis in the design of the first tall buildings in Mexico. The primary aim of this paper is to review the seismic design criteria for the case under study in order to contribute to the state of the art in Modern Heritage. The review includes a comparison between the dynamic characteristics estimated during the design and the results of recent ambient vibration tests and numerical modeling. Several sources of error among the design criteria were identified. Notably, the fundamental period estimated during the design was 38% larger than the experimental value due to an underestimation in stiffness, which introduces significant uncertainty into the design. Overall, the review shows the evolution of seismic analysis over time and provide valuable insights for the study of similar buildings.

The impact of the destruction of the Kakhovka reservoir dam on the oceanographic conditions in the north-western part of the Black Sea according to the results of modeling

Based on the results of numerical modelling, characteristic features of distribution of transformed and polluted waters of the Dnieper River in the water area of the north-western part of the Black Sea (NWBS) are determined and analyzed. This pollution of the marine environment resulted from the extremely large man-made flood caused by the destruction of the Kakhovka Reservoir dam by the Russian occupation forces in June 2023. Various types of pollutants, which contained in the Kakhovka Reservoir, in the lower Dnieper River and in the bottom sediments, were carried out into the sea by the flood discharge. A significant amount of pollutants was washed into the sea from the flooded areas of the lower Dnieper basin. Special attention is given to changes in oceanographic conditions in the Dnieper-Bug estuary region (DBR) of the Black Sea, which determine the extent of marine pollution. Sea water salinity was used as an indicator of the degree of infiltration of polluted seawater from the estuary into the sea. It was identified that the least transformed river waters with low salinity correspond to high pollution levels. Delft3D-Flow Flexible Mesh hydrodynamic model, developed by Deltares, was used in this study. The simulation was performed for the time period 01 to 30 June 2023. During the first days after the dam break the desalinated and polluted transitional waters, flowing from the Dnieper-Bug estuary, spread over the entire water column down to 15-20 m depth in the DBR area. In this case, the spreading of transitional waters was atypical, as it usually occurs only within the thin near-surface layer of the sea. By mid-June the flow of transitional water with a salinity of 4-6 ‰ covered the entire water column from surface to bottom near the northern coast of the NWBS and over the Odessa Bank. This was facilitated by the supermassive volumes of transformed Dnieper river waters flowing out over a short period of time due to dam break, as well as by the resulting intense gradient currents and mixing caused by spatial gradients in the velocity of the generated currents. The width of the desalinated water plume and its area in the bottom layer were smaller than in the surface layer. The largest vertical salinity gradients were formed to the south of the Odessa Bank, where salinity was 4-6 ‰ in the surface layer and 14-17 ‰ in the bottom. Dilution of the desalinated water plume in the bottom water layer was much more intensive than in the surface water. The character of water circulation pattern in the northern part of the NWBS in the first days after the inflow of transient waters from the Dnieper-Bug estuary was determined by the runoff gradient currents, which later were replaced by wind-driven currents in the Odessa area and over the Odessa Bank, and by the meandering flow of gradient density currents further south. The findings of this study contribute to a better understanding of the impact of the inflow of transformed river waters from the Dnieper-Bug estuary on the variability of oceanographic characteristics and the ecological state of marine waters in the Dnieper-Bug region of the northwestern Black Sea.

2D discrete element analysis of the footing above excavated circle in soil

The bearing capacity and settlements of surface foundations located on a soil slope are the important issues that have to be considered by geotechnical engineers for the design. The presence of an underground void beneath the footing can affect the foundation stability and can lead to serious structure damages. In this study, the results of two-dimensional (2D) discrete element (DE) and finite element (FE) analyses of a surface footing on a soil slope above a void are presented. To validate the numerical model results, the DE results obtained have been compared with experimental test presented in the previous study. After validation of the DE numerical model, parametric studies were carried out to evaluate the effect of important factors on the surface footing performance. The studied parameters include the horizontal spacing of the void axis relative to the slope edge (SH), the vertical spacing of the void crown relative to the footing base (SV), the horizontal spacing of the footing edge relative to the slope edge (De) and the void diameter (Dv). The effects of these parameters on the pressure-settlement curves and the contact force distributions in the soil slope are presented and discussed. The results showed that the footing bearing pressure increases with an increase of SH, SV and De but decreases when Dv increases. The behavior of a surface footing on a soil slope above a void significantly depends on the SV value.