Physical Modeling Method Research Articles

Some results of laboratory researches of the vibration effect on the cohesive fine-dispersed geomaterials strength characteristics

The effect of strength characteristics, and specifically the cohesion and the angle of internal friction, on the conditions for the displacement and compaction of dispersed materials is described. The employment of the physical modeling method in the researches of these parameters changes under vibration is justified. The laboratory stand, a measuring complex and a technique for experiments performed in two stages are presented. At the first stage, the dispersed material was loaded statically, and the efficiency of moisture and clay content on its strength characteristics was determined. At the second stage, the vibrational acceleration effected, additional to the static one, on the change in the effective cohesion and the effective angle of internal friction of dispersed materials of various compositions and moisture was considered. Recommendations on using of the vibration impact on fine-dispersed materials regimes, directed at the efficiency increase and reducing the energy intensity of the forced processes of their movement and compaction, have been established.

Numerical and Experimental Investigations on Hydrodynamic Performance of a Newly Designed Deep Bottom Trawl

In this paper, a new type of bottom trawl was designed for target fishing vessels to use in deep-water fishing grounds. The trawl’s hydrodynamic performance was investigated using numerical simulation and physical modeling methods, and a numerical model based on the finite element method was proposed for estimating hydrodynamic forces and predicting performances. A series of physical model tests based on Tauti’s law were carried out in a towing tank to explore the hydrodynamic performance of the trawl and to assess the applicability of the numerical simulation method. The results showed that the working towing speed of the trawl was 3.5 kn. The drag force and the height of net opening were 50 kN and 5.62 m, respectively, and the swept area was 128 m2 at that speed. The simulated result was close to the experimental result, with a maximum relative error less than 20%, and an average relative error of 10%. The net shape and tension distribution of the trawl were analyzed using the numerical simulation method, and the hanging ratio in T-direction of the mesh of the codend was 0.25 at the working towing speed. The newly designed deep bottom trawl had a superior hydrodynamic performance for high catch efficiency and selectivity and may be applied to commercial fishing operations.

Machine Learning Aids Early Detection of Stuck Pipe in Extended-Reach Wells

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 206516, “Stuck-Pipe Early Detection in Extended-Reach Wells Using Ensemble Method of Machine Learning,” by Rushad Ravilievich Rakhimov, SPE, Schlumberger, and Oleg Valerievich Zhdaneev, SPE, and Konstantin Nikolaevich Frolov, SPE, Ministry of Energy of the Russian Federation, et al. The paper has not been peer reviewed. The objective of this paper is to describe the experience of using a machine-learning model prepared by the ensemble method to prevent stuck-pipe events during construction of extended-reach wells. The tasks performed include collecting, analyzing, and cleaning historical data; selecting and preparing a machine-learning model; and testing it on real-time data by means of a desktop application. The idea is to display the solution at the rig floor, allowing the driller to take actions quickly for prevention of stuck-pipe events. Problem Analysis Packoff is the blockage of the annular space with drilled cuttings or parts of rocks fallen from wellbore walls. In a packoff situation, circulation is severely limited or impossible. With an inadequate response to packoff, fracturing of rocks below the bottomhole assembly (BHA) can occur, which leads to losses of drilling fluid and possible kick. In addition to time spent and technological risks, high expense is possible. In a worst-case scenario, the BHA can be left in hole and the bore must be redrilled, leading to a multimillion-dollar financial loss caused by nonproductive time. Packoff events fall mainly into two categories: - Caused by a cuttings bed that occurs when drilled cuttings are caught up while backreaming out of hole too promptly - Caused by wellbore collapse because of insufficient mud properties During the past 10 years, 28 wells have been drilled in the field of interest. Two hundred and twenty-seven incidents associated with stuck-pipe events have been registered. The light cases required an additional rereaming of the problematic interval, with a loss of time of up to 20 minutes. The most severe cases resulted in multimillion-dollar financial losses because of the BHA being lost in hole and the time spent on redrilling the wellbore. Classification of the incidents showed that 24 cases (11%) belong to the differential type of sticking, while 17 cases (8%) belong to the wellbore-geometry type and 186 cases (81%) to packoff events. The data collected at the field show that packoffs were encountered only during backreaming operations. Packoffs evolve rapidly. Thus, in most cases on the studied field, the time interval between trouble-free operation and sticking events is between 20 and 90 seconds (Fig. 1). Unlike physical modeling methods, machine-learning methods serve as a base for development of tools that work solely from historical data, allowing a more-precise simulation of real parameter behavior. Another advantage of machine-learning methods is the ability to select only the best historical cases for use. However, the use of historical data for prediction of downhole accidents in the well-construction process is not a novel approach. It has been used in the industry for more than 30 years. The complete paper includes an extensive discussion of examples in the literature.

Method of heat and mass transfer calculation of cooling technical water process at CHP plant when cooling pond with spray devices is operated

The generation of electrical energy at thermal and nuclear power plants is associated with outward heat transmission of large amount. Cooling devices (cooling towers, spray pools, reservoirs) are used for its utilization. The increase of the efficiency of the cooling capacity of this equipment in the circulating water supply system of the CHP plant is occurred due to a decrease of temperatures that meet the optimal technical and economic performance of the facility. The studies of I.I. Makarova, V.A. Gladkova, B.S. Farfarovsky, Z.K. Maimekova, S.A. Suprun are devoted to these issues. The aim of the study is to develop a methodology to calculate the process of cooling technical water to create an operating temperature mode of the equipment during condensation of the waste heat of steam turbines and to minimize the amount of additional water from the Tom River in the warm season. To evaluate the operation of spray devices the authors have used experimental data obtained during the survey of the cooling pond of the West Siberian CHP plant in Novokuznetsk city and methods of physical modeling of heat and mass transfer. To increase the efficiency of technical water cooling at the CHP plant, it is proposed to install spray devices in addition to the existing cooling pond. A method has been developed to calculate the process of water cooling in spray devices during collaboration with a cooling pond. The method is based on the calculation of the optimal water temperature at the intake point in accordance with the operating parameters of turbine generator condensers. The method differs from the existing ones as it considers the influence of heat transfer and mass transfer phenomena in the boundary layer near the surface of dispersed drops water. The experimental and calculated results confirm that the use of spray devices in the cooling pond reduces the amount of additional water taken from the Tom River compared to its limit flow by almost 10 times at the established temperature difference during the condensation of exhaust steam in the summer period of the year. The method to calculate the cooling of technical water in a cooling pond with spray devices is recommended for implementation at the West Siberian CHP plant in Novokuznetsk city.

Anisotropic metadielectric converter

Purpose. Investigation of the peculiarities of the electric field energy conversion by an anisotropic meta-medium with a negative value of the dielectric constant in one of the selected main crystallographic directions. Methodology. Research was carried out using methods of physical and mathematical modeling of anisotropic metadielectric converter; using methods to optimize the function of the dependence of the conversion factor m, anisotropic metadielectric converter, on the angle α between one of the crystallographic axes and the edge of the platinum a, at fixed anisotropy coefficients of metadielectric material. Findings. For the first time, the peculiarities of the electric field transformation by an anisotropic meta-medium with a negative value of the dielectric constant in one of the selected main crystallographic directions were studied. It is established that at the moment of application to the upper and lower faces of the anisotropic metadielectric plate, which is the basis of the anisotropic metadielectric converter, some potential difference leads to polarization of its volume and the emergence of both longitudinal and transverse components of the vortex electric field. This situation leads to axial folding of its internal field, which in turn causes the appearance of micro-vortices of the electric field, given by the expression , where - the circular time of rotation of the micro-vortex, and signs "+" and "-" - indicate the direction of its rotation. Such axial electric micro vortices are an efficient mechanism that pumps energy between the physical vacuum and, in our case, the anisotropic metadielectric plate of the transducer. The dependence of the transformation coefficient m of this medium on the value of anisotropy is analyzed. Studies have shown that in the interval the value of m is characterized by a negative value, and in the interval – positive, this allowed us to determine the areas of stable existence of different types of energy. The use of metadielectric material in comparison with the classical one is characterized by values of m>1. Note that in some cases there is an abnormal increase in the coefficient. Originality. Using the representations of vortex electrodynamics, the mechanism of energy interaction between the vortex electric field of an anisotropic metaenvironment and the physical vacuum is proposed. Practical value. A model of the original design of an anisotropic metadielectric converter is proposed. Areas of its practical use in the form of generators of electricity, heat and cold are determined, calculated expressions for their efficiency are in the range η = 0.5 ÷ 0.98, and the cooling temperature can reach the temperature of liquid helium.

Characterization of mineral and pore evolution under CO2-brine-rock interaction at in-situ conditions

Herein, a method of physical modeling of CO2-brine-rock interaction and in-situ characterization of mineral and pore evolution is established. The nested preparation and installation of the same sample with different sizes could protect and keep the integrality of the millimeter-size sample in conventional high-temperature and high-pressure reactors. This paper establishes a procedure to obtain the three-dimensional in-situ comparison of minerals and pores before and after the reaction. The resolution is updated from 5-10 µ m to 10 nm, which could be helpful for modeling CO2-brine-rock interaction in unconventional tight reservoirs. This method could be applied to CO2-enhanced oil recovery as well as CO2 capture, utilization, and storage scientific research. Furthermore, it may shed light on the carbon sequestration schemes in the Chinese petroleum industry. Cited as: Wu, S., Yu, C., Hu, X., Yu, Z., Jiang, X. Characterization of mineral and pore evolution under CO2-brine-rock interaction at in-situ conditions. Advances in Geo-Energy Research, 2022, 6(2): 177-178. https://doi.org/10.46690/ager.2022.02.09

A three-dimensional model study of lateral pressure manifestation in gorge dump overburden

Today the development of upland quarries with the formation of multi-tiered dumps of overburden rock mass in complex conditions of mountainous terrain and limited land resources still remains a problem. The conducted analysis has shown that the practice of designing of multi-tiered dumps in gorges lacks detailed consideration of the issues determining the stress distribution in the dump body depending on the dihedral angle formed by the slopes of the side faces of the gorge. The point is that the process of overburden dumping is accompanied with the transmission of stress forces to the central axial plane of the dump body formed in the gorge from the side of the gorge inclined surfaces. At the same time, the inclined component of stresses is due to the mass of overburden rocks dumped onto the inclined side surfaces of the gorge. Being directed at an angle to the shear forces acting in the dump, these lateral stresses play a positive role in the acceleration of rock mass consolidation in the clamped environment during the overburden dump formation. The decrease in dump shear forces leads to the increase in dump stability. It also allows to determine the rational volumes of overburden to be laid as well as the main parameters of a multi-tiered dump. It should be noted that there are significant difficulties in identifying and objective assessing the nature of occurrence and distribution of stress forces in the dump being constructed in the gorge using graphic-analytical methods. In the course of the presented study, the author made an attempt to identify and register stress forces in the body of a multi-tiered overburden dump formed in the gorge using physical modeling methods. For this purpose, a three-dimensional model test bench of a multi-tiered dump has been developed. This test bench allows to solve a three-dimensional problem using the method of physical modeling and, identify the stress variation patterns in the central axial plane of the dump model depending on the inclination angles of the side surfaces of the gorge.

Deep learning model based on urban multi-source data for predicting heavy metals (Cu, Zn, Ni, Cr) in industrial sewer networks

The high concentrations of heavy metals in municipal industrial sewer networks will seriously impact the microorganisms of the activated sludge in the wastewater treatment plant (WWTP), thus deteriorating the effluent quality and destroying the stability of sewage treatment. Therefore, timely prediction and early warning of heavy metal concentrations in industrial sewer networks is crucial. However, due to the complex sources of heavy metals in industrial sewer networks, traditional physical modeling and linear methods cannot establish an accurate prediction model. Herein, we developed a Gated Recurrent Unit (GRU) neural network model based on a deep learning algorithm for predicting the concentrations of heavy metals in industrial sewer networks. To train the GRU model, we used low-cost and easy-to-obtain urban multi-source data, including socio-environmental indicator data, air environmental indicator data, water quantity indicator data, and easily measurable water quality indicator data. The model was applied to predict the concentrations of heavy metals (Cu, Zn, Ni, and Cr) in the sewer networks of an industrial area in southern China. The results are compared with the commonly used Artificial Neural Network (ANN) model. In this study, it was shown that the GRU had better prediction performance for Cu, Zn, Ni, and Cr concentrations, with the average R2 significantly increased by 12.35%, 11.94%, 9.21%, and 8.13%, respectively, compared to ANN predictions. The sensitivity analysis based on Shapley (SHAP) values revealed that conductivity (σ), temperature (T), pH, and sewage flow (Flow) contributed significantly to the prediction results of the model. Furthermore, the three input variables including air pressure (AP), land area (A), and population (Pop.) were removed without affecting the prediction performance of the model, which maximized the modeling efficiency and reduced the operational cost. This study provides an economical and feasible technical method for early warning of abnormal heavy metal concentrations in urban industrial sewer networks.

The influence of mineral inclusions on the heat efficiency of the enclosing construction from wood-cement composite in the rural house building

Reducing the cost of maintaining housing objects inevitably leads to the development of energy-saving technologies and building materials. Cost reduction is achieved by reducing heat losses through walls and floors of buildings and structures. Wood-cement composite materials are attractive not only from the point of view of energy saving and reducing construction costs, but also as materials in the production of which woodworking waste is used, therefore, the problem of complex waste-free use of raw materials is solved. In the course of the research, the influence of mineral inclusions on the indicators of the thermal efficiency of enclosing structures made of wood-cement composite (wood concrete and sawdust concrete) was determined. The work was based on the use of physical modeling methods (finite element method) implemented in the Elcut software package. The value of the heat loss indicator, depending on the type of wood-cement composite and operating conditions, was 34.2…. 54.8 W/(m2·°C). The indicator of resistance to heat transfer is 0.58 … 2.2 (m2·°C)/W. The presence of mineral inclusions worsens the thermal performance of the enclosing structure by an average of 7%. The results obtained can be used in the design and operation of building structures made of wood-cement composites.

Dynamics of the Rolling Stock and the Choice of Parameters of Vibration Dampers

Modern railway rolling stock should meet requirements regarding comfort (maximum travel speed with minimum vibrations of wagons, noiselessness of movement, etc.).To eliminate the influence of dynamic loads, rolling stock is equipped with vibration dampers. The objective of the work is to select the parameters of the vibration dampers of rolling stock, depending on its characteristics, to ensure the due indicators of comfort and safety of transportation of passengers and goods by rail. To achieve this objective, applied methods of mathematical modelling were based on numerical programming of operation of dynamic systems. The indicators of vibration dampers are evaluated according to the results of studies of the dynamics of the rolling stock (in particular, of vibration protection rates).Assessment of dynamic state of the rolling stock implies application of methods of mathematical and physical modelling, which include the development of a physical and mathematical model, a calculation algorithm, and computer programming. The study of the mathematical model by numerical methods makes it possible to carry out a multifactorial experiment using a large number of input parameters (factors) and to select the characteristics of vibration dampers that are optimal for the conditions under consideration.To solve dynamic problems, the harmonic perturbation model, which is the most widespread, was specified in the form of a sinusoid with a period corresponding to the rail length.A quantitative assessment of the vibration process (frequency, amplitude) makes it possible to identify the main processes occurring in the system under consideration under various types of external load. The introduced assumptions related to rigidity, mobility and geometric immutability of the system allow determining the methods for obtaining a mathematical model and considering the vibrations as flat ones.The equations were solved in MathCad Prime 4.0 package using the Runge–Kutta method with automatic step selection. The subsequent study of the properties of the dynamic system was carried out by changing the resistance parameter of dampers of the first stage of spring suspension, while recording the values of the amplitude of the vibrations of the system and the period.The analysis of the results has shown that the vibration period of the body and bogies under any changes in the resistance parameter of the damper remains unchanged, while rational parameters of resistance of axle box dampers have been revealed for specified indicators. Hydraulic vibration dampers with the revealed parameters used on rolling stock help to reduce wear and damageability of running gears, improve ride comfort and traffic safety, as well as to reduce repair and maintenance costs.

МОДЕРНИЗИРОВАННАЯ УСТАНОВКА ДЛЯ ФИЗИЧЕСКОГО МОДЕЛИРОВАНИЯ ПРОМЫВКИ ЗАСОЛЕННЫХ ПОЧВ

The purpose of the study is to improve the design of the installation through the use of soil moisture concentration sensors and digital LCR meter XJW01. The digitalization of hydrotechnical melioration of agricultural lands in the Russian Federation requires the active use of mathematical models for the movement of moisture fl ows, nutrients, air, and heat in the soil profile. The parameters of these flows in the laboratory are determined by the methods of physical modeling. Improving the design of installations for the physical modeling of soil processes increases the accuracy of measurements and reduces the labor intensity of work. The modernized facility for physical modeling of saline soil leaching includes electrical sensors for measuring the concentration of soil moisture. The sensors are equipped with conductive plates and conductive windings. Digital LCR meter XJW01 automatically detects the sensor as an electrical oscillatory circuit and fixes its quality factor. The quality factor of the sensor depends on the concentration of soil moisture that fi lls its body. The operating prototype of the installation was tested. In the concentration range of NaHCO3 solution from 0 to 350 mmol/dm3 , the quality factor of the sensors varies from 282±2.1 to 221±2.7 (signifi cance level P = 0.99, number of degrees of freedom k = 4, and Student’s test t = 4.60).

Changes in the initial parameters of waves caused by distortions in the scale of a hydraulic model

Introduction. The distorted scale method is often used to develop physical models of hydraulic structures. Notably, scientific researches concerning the methodology of distortions are quite rare, especially those that are focused on the modeling of wind waves. In the modern practice, scale distortions only affect the underwater topography and hydraulic structures. In this case, initial waves remain unchanged, and this can lead to errors in the wave mode at the control points of a model. Given the data on errors, the author considers the changes in the parameters of initial waves, if the scale of a physical model is distorted.
 Materials and methods. The author used methods of physical and numerical modeling. Experimental studies were conducted in a wave flume and a wave pool that had a wavemaker. In the course of the experiments, the initial wave mode was changed and the parameters of waves were measured at the control points of distorted physical models. Numerical mode­ling was employed to analyze the computational patterns similar to the physical models.
 Results. The author used physical models featuring varying degrees of distortion to obtain a collection of the wave mode data under the conditions of the wave transformation and diffraction. Physical and numerical modeling results are compared. The author provides an assessment of the results attained by changing the parameters of initial waves and distorted physical models.
 Conclusions. The scale distortion triggers changes in the wave mode that may not be easy to control and correct. This fact must be taken into account when distorted hydraulic models are developed. This approach demonstrates varying efficiency if applied to different physical models featuring characteristic processes.

УДОСКОНАЛЕННЯ ВЛАСТИВОСТЕЙ СПЕЦІАЛЬНИХ СВЕРДЛОВИННИХ ТЕХНОЛОГІЧНИХ РІДИН ПРИ РОЗРОБЦІ РОДОВИЩ

Purpose. Analytical, laboratory and industrial study, as well as analysis of the basic factors of rationalization of the use of special process fluids in the processes of cleaning, casing and cementing of boreholes drilled in difficult geological and lithological conditions, through the development and implementation of innovative technical and technological techniques and methods. Methodology. The study of borehole circulation, rock cutting and regime-technological processes was carried out using modern methods of physical bench modeling, instrumentation and related materials, as well as processing the results of studies in the EXCEL, MATHCAD environment. Laboratory control methods were used to study the technological characteristics of special fluids and the patterns of operation of the drilling tool, which are working methods for determining the main characteristics of the formation processes of the wellbore at different stages of its construction. The design of the stabilized buffer mixture was carried out using the method of orthogonal central compositional planning. Findings. The physicochemical properties and influence of washing liquids of various compositions on the rocks of the sedimentary and metamorphic complexes have been studied from the standpoint of their hydration and the ability for surface adsorption interaction. The mechanism of the flow of well circulation processes with the participation of flushing fluids, as well as its consequences for the appearance of prerequisites for reducing the strength of the rock mass and reducing the loss of mechanical power in the wellbore, has been studied. The principles of constructing optimal schemes for the regeneration of a flushing liquid based on the use of sedimentation phenomena are considered. The development and clarification of downhole factors in the behavior of buffer fluids, taking into account their provision for the complete exclusion of the manifestation of violations of the integrity of the cement stone. Originality. Rationalization of indicators of the well construction process can be successfully achieved on the basis of directed regulation and adaptation of the main physical and chemical properties (density, viscosity, surface tension, content of lubricating impurities) of special process fluids for specific well geological and technical conditions. Practical value. The presented research results provide the basis for building a closed engineering cycle for designing and using special process fluids in order to reduce the time for well construction and eliminate the cost of complex repair and restoration work in them. Keywords: flushing liquid, surfactant, well, drilling, buffer system, fastening, cement stone, mine.

Physical-data Fusion Modeling Method for Energy Consumption Analysis of Smart Building

The energy consumption of buildings accounts for approximately 40% of total energy consumption. An accurate energy consumption analysis of buildings can not only promise significant energy savings but also help estimate the demand response potential more accurately, and consequently brings benefits to the upstream power grid. This paper proposes a novel physical-data fusion modeling (PFM) method for modeling smart buildings that can accurately assess energy consumption. First, a thermal process model of buildings and an electrical load model that focus on building heating, ventilation, and air conditioning (HVAC) systems are presented to analyze the thermal-electrical conversion process of energy consumption of buildings. Second, the PFM method is used to improve the accuracy of the energy consumption analysis model for buildings by modifying the parameters that are difficult to measure in the physical model (i. e., it effectively modifies the electrical load model based on the proposed PFM method). Finally, case studies involving a real-world dataset recorded in a high-tech park in Changzhou, China, demonstrate that the proposed method exhibits superior performance with respect to the traditional physical modeling (TPM) method and data-driven modeling (DDM) method in terms of the achieved accuracy.

過酷事故時の原子炉格納容器・原子炉建屋の安全性解析コードBAROCによる原子炉建屋内気相挙動解析

We developed the CFD analysis code BAROC for the reactor containment vessel and reactor building in a situation of severe accident. BAROC can analyze the three-dimensional thermal-hydraulics of multi-component gas and FP (fission product) aerosol in detail. By applying the implicit method and partially parallel processing, high-speed calculation is possible even for large-scale systems. The physical model and numerical solution method used in BAROC, as well as the results of analysis of the leakage and diffusion behavior of hydrogen and FP in the reactor building at the time of the accident of the Fukushima Daiichi Nuclear Power Plant are introduced.

Series or Parallel? An Exploration in Coupling Physical Model and Machine Learning Method for Disaggregating Satellite Microwave Soil Moisture

Remotely sensed soil moisture (SM) dataset with well accuracy and fine spatiotemporal resolution is very valuable in various fields. Downscaling is a promising way to obtain such an SM dataset. There are currently two basic methodologies in the downscaling with satellite datasets, i.e., the machine learning (ML) methods and the physical or semi-physical (PH) models. This study focuses on exploring feasible ways to integrate them for boosting the performance of downscaling. Here, three parallel modes i.e., arithmetic average (Ari), geometric average (Geo), and weighted average (Wei), and two series modes i.e., first PH then ML (PH-ML) and first ML then PH (ML-PH) were developed and evaluated. A representative of PH, DSCALE_mod16, and three ML algorithms Random Forest, XGBoost, and LightGBM were used in this study. Microwave SM datasets from Soil Moisture Active and Passive Mission (SMAP), satellite datasets from MODIS, and in-situ SM observations spanning from April 2015 to December 2018 were employed in the evaluation. Spatial dynamic range, energy conservation, and precision preservation analyses were conducted as evaluation methods. Results demonstrated the PH-ML series mode outperformed the other coupling modes, which was even better than the better one of the PH and ML. The PH can first generate a valuable initial estimate, and the initial estimate’s advantages can be preserved while its errors can be suppressed by the ML. Resultantly, the ideology of first using the PH to obtain an initial estimate and then putting the initial estimate into the ML is suggested for further microwave SM downscaling.

Influence of ferrimagnetic resonance on conversion of electromagnetic energy by a YIG resonator into mechanical one

Using the method of physical modeling, an algorithm for calculating the force with which a standing electromagnetic wave acts on a ferrite sphere of arbitrary diameter placed in a constant magnetic field is obtained. The value of constant magnetic field intensity provides appearance of ferrimagnetic resonance. Dependence of the magnetic field of an electromagnetic wave in the middle of a ferrite sphere on the size of its resonant radius and spherical coordinates are studied. In the center of the ferrite sphere, the resonance radius of which is 4.2634 mm, the microwave magnetic field strength is 83796 times greater than the magnetic field strength in the incident plane polarized wave. Mean-square value of the magnetic field strength over the volume of the sphere increases 4.8 times. Standing wave, formed in a free space with power flow density of 622 kW/m2 and wavelength of 3.2 cm, reflects from metallic shield placed at a distance of λo/8 + nλo/2, n = 0, 1, 2, 3… measured from the center of ferrite sphere and impacts with force of 0,12 N on ferrite sphere with resonance radius of 4,2634 mm. The results of the calculated force acting on the YIG – resonator coincide with the experimental results given in the well-known works (the power flux density is 43 kW/m2, the radius of the ferrite sphere is 1.775 mm, the force is 6 ± 0.5 μN) within the measurement error. Application of spatial resonance, standing electromagnetic wave and YIG resonator allows to increase of energy conversion factor of microwave energy conversion into mechanic one 8,6·104 times in compare to application of ferrite cylinder only in known papers. The research results can be used by the developers of converters of microwave energy into mechanical energy.

ОСОБЛИВОСТІ ЗАСТОСУВАННЯ МЕТОДІВ ФІЗИЧНОГО МОДЕЛЮВАННЯ ДЛЯ АНАЛІЗУ ПРОЦЕСУ ПРИЗЕМЛЕННЯ ПАРАШУТНИХ ПЛАТФОРМ НА НАДУВНІ ПОВІТРЯНІ АМОРТИЗАТОРИ

Research has been carried out aimed at developing the theoretical bases of physical modelling of landing processes of parachute platforms on inflatable air shock absorbers. At the same time, the features of the application of physical modeling methods for solving this task are considered. The conditions, landing features and operation of parachute platform devices at landing on inflatable air shock absorbers are determined. It is shown that presently parachute-depreciation systems have become widespread, in which soft tissue shells are used, filled through the inlet openings with atmospheric or air injected from gas bottles air. The operation of these devices is based on the compression of air in the shell and expiration of him through exit holes (valves). At the same time, air inflatable shells absorb the kinetic energy of the impact, controlling the release of air through exit holes.It has been established that the most effective method for studying the behavior of a dropped vehicle is physical modelling, which uses a free-flying dynamically similar model (FDSM) or stand dynamically similar model (DSM) of a dropped object as an research object. Modeling of landing processes of parachute platforms on inflatable air shock absorbers is not related to the dynamics of the flight and air flow around surfaces. Therefore, for this task, the existing developments in physical modelling of dynamics flight cannot be applied, and for the theoretical substantiation of the dynamic similarity to modeling motion, it makes sense to use the laws of gas dynamics in regard to air shock absorbers.

Transient physical modeling and comprehensive optimal design of air-breakdown direct-current triboelectric nanogenerators

Direct-Current Triboelectric Nanogenerators (DC-TENGs) achieves an direct-current (DC) output instead of traditional alternating-current (AC) output of TENG. Among the various structure designs of DC-TENGs, the air-breakdown DC-TENG has created a record of energy density and an almost constant-current output, which has great potential in practical applications. This paper proposes a transient physical-field model and carries out comprehensive optimal design for air-breakdown DC-TENG. The beneficial breakdown domain (BBD) and harmful breakdown domain (HBD) are introduced to reveal the dynamic mechanism that distinguishes the DC-TENGs from AC-TENGs. Indexes of the breakdown charge ratio (BCR) and leading charge density (LCD) are defined to evaluate the extent to which the high-density surface charge is effectively exploited in electricity generation based on the beneficial breakdown effect. The output characteristics of air-breakdown DC-TENGs are theoretically analyzed, revealing the influence of the load resistance, device structure parameters, and initial charge density. Therefore, the optimal design of air-breakdown DC-TENGs is carried out with a high output power and low matching resistance. Finally, these superior performances are verified by experiments, so that the proposed transient physical model and comprehensive optimization method can be reliably extended to the design of all types of air-breakdown DC-TENG, and promote its application in a wide range of fields.

A study on resonance characteristics of hydraulic structures and buildings conducted using small-size models

Introduction. The study focuses on resonance characteristics of a hydraulic engineering structure, such as a groin, land retention works on an artificial island, and a school building. Any structure, exposed to dynamic effects of natural or man-induced origin, can be validly simulated as a mechanical resonator. Models are made of materials that have electro-elastic properties allowing to measure responses to induced oscillations, or changes in an alternating electric field, and reevaluate the physical characteristics later.
 Materials and methods. Small-size physical models of structures are made of electro-elastic materials, such as organic glass and ABS plastic, used for 3D printing. A laboratory test bench, composed of an oscillator and a personal computer, used as an oscillograph, was applied to conduct the testing. Mathematical modeling was performed using SolidWorks software packages. Oscillation modes and structural responses, featuring different response amplitudes, were identified. Models of structures were studied in different contexts, including restraint and free bearing.
 Results. It has been found that frequencies of the first mode of oscillations in a restrained model correspond to the fourth mode of a model in case of free bearing. Mutual correlation of eigenfrequencies of oscillations in small-size models, made of ABS plastic and organic glass, is demonstrated.
 Conclusions. The applicability of ABS plastic as the material of small-size physical models of buildings and structures has been proven for the purpose of identifying resonance frequencies of the prototypes. The co-authors have developed an integrated physical and mathematical modeling method that entails the use of SolidWorks software packages. This method allows to identify resonance frequencies, which are most dangerous for structures. Different structure support patterns allow to apply the geometric scale to obtain resonance frequencies when translating small-size model results to natural values and, hence, identify the vulnerability of structures to dynamic effects.