Passage Of Wave Research Articles

Обследование скрытых участков стальных труб малого диаметра с применением ультразвуковой дефектоскопии

According to the current regulatory documents, as the established service life of gas pipelines for various purposes expires, they must be inspected in order to assess the current technical condition, make a decision on the residual life and the possibility of further operation at hazardous production facilities, as well as other buildings and structures. The possibility is considered related to using ultrasonic testing for detecting damage of corrosion origin in the sections of such pipelines hidden from the direct observation in interfloor ceilings and passages through the walls of buildings at the facilities in various branches of industries, as well as in gas distribution and gas consumption systems, and water pipelines. In addition, the possibility of identifying layered deposits of various origins in the cavity of small-diameter steel pipes is considered. At energy facilities, as well as in water supply pipelines, such deposits can lead to a significant reduction in the flow area of the pipeline, up to its complete blocking. Deposits inside the pipelines form an anisotropic layered medium, and the passage of ultrasonic waves through it has a number of features that prevent the use of traditional ultrasonic echo testing. For small-diameter pipes, the criterion is given under which it is possible to perform «remote» (waveguide) ultrasonic testing of the hidden sections of pipes at a distance of up to 600 mm. It is illustrated how, from such a distance, it is possible to detect corrosion deposits in pipes by ultrasonic testing methods using phased array antennas. At the same time, it is possible to assess the thickness («power») of layered deposits and their structure even when the passage section of the pipeline is filled with such deposits up to 100 %. Use of the methods presented in the article allows to increase the accuracy of calculating the residual life of the pipeline and reduce the uncertainty in setting safety factors in such calculations.

STUDIES ON KINETICS AND THERMODYNAMICS OF EFFECTS OF PRIMARY COLOURS ON PHOTOCHEMICAL REACTIONS: PHOTOSYNTHESIS IN Loudetia arundinacea IN FOCUS

Light, especially green light in sunlight, is reflected alongside absorption of other wavelengths of electromagnetic radiation by leaf before photosynthesis can take place, with no application of extra external energy and without pollutants. Green being one of the primary colours of white light makes the investigation of effect of irradiation of elephant grass (Loudetia arundinacea) with primary colours. Duration of irradiation with LEDs and sunlight ranged from 300s to 1800s, at 300k. Primary colours were absorbed with 0.01M KMnO4, 0.01M methyl orange 1M CuSO4 and 1M NiSO4. Total carbohydrate formed by L .arundinacea after irradiation obtained using anthrone test became a measure of photosynthesis. Rate of photosynthesis in 30 minutes in L. arundinacea decreased in the order; BLED>WLED>GLED>RLED; also, W-b>W-g>W-br>W-r; and S-b>S-br>S>S-g>S-r. While BLED with TCPR of 15.62±0.001mg/100mg, is most favorable to photosynthesis, W-b had its TCPR reduced to 8.85±0.001mg/100mg, and W-r, as well as S-r had their TCPR as 1.91±0.001 and 5.09±0.001mg/100mg respectively, being higher than pure RLED with 0.26±0.001mg/100mg. Influence of green light over red light in W-b causes higher TCPR than when red light combines with blue light in W-g. Passage of other waves of electromagnetic spectrum causes elevated TCPR for S-b, S-br and S-r compared to those for W-b, W-br and W-r.

Intact peritoneum in a child with ileal perforation from a firearm injury

Introduction Indirect intra-abdominal injury with an intact peritoneum following close passage of highly energized projectiles is an uncommon but clearly described phenomenon; likewise delayed gastrointestinal perforation hours or days after passage of a high-energy stress wave from primary blast injury is uncommon. Awareness of these two rare occurrences is required to ensure delayed perforations are diagnosed and managed in a timely manner. Case report An 8-year-old male child sustained a shotgun injury to the right elbow and the abdominal wall only of the right hypochondrium. Due to a non-salvageable joint injury, he underwent amputation of the right upper limb above the elbow, but on the third day of admission, he developed peritonitis and an X-ray revealed pneumoperitoneum. On abdominal exploration, two small ileal perforations were found without penetration of the peritoneum or diaphragm. The ileal injuries were primarily repaired and the postoperative course was uneventful. Conclusion Indirect injury to abdominal viscera from the primary blast effect of close passage of high-energy projectiles resulting is rare and can have significant consequences if not diagnosed and managed early.

Мodel of diffraction of electromagnetic waves on explosive objects

A model of electromagnetic wave diffraction on an explosive object without metal structural substances is proposed. The properties of the materials of the most common anti-personnel mines were analyzed and it was established that their shell is dielectric, and explosive substances are divided into two groups depending on their dipole moment. In particular, the explosive substances such as hexogen, pentaerythritol tetranitrate, and mercury fulminate with zero dipole moment and according to their electromagnetic properties, they belong to ideal dielectrics. The explosives trinitrotoluene, tetryl, lead trinitroresorcinate, and lead azide should be considered as low-loss dielectrics. An electrodynamic model was built to calculate the reflection coefficients and the passage of electromagnetic plane waves of the microwave range through the multilayer structure of an explosive object. To determine the equivalent wave resistance of the multilayer structure of an explosive object, the use of the theory of long lines is proposed. It is established that for microwave radiation, the layers of the case of explosive objects made of dielectric substances can be neglected due to their small thickness. The modeling results show that most anti-personnel mines have a low reflection coefficient, which makes them difficult to detect, but at the same time increases the amount of energy that can pass deep into the body of the explosive substance. It has been shown that explosive objects with dipole explosive substances are capable of absorbing electromagnetic radiation energy. The obtained results allow us to qualitatively assess the susceptibility of explosive substances to their remote detonation by irradiation with powerful pulses of electromagnetic radiation in the microwave range.

Упругие резонансы в структуре: тонкая магнитная пленка – толстая упругая подложка

The task about excitation of connected magnetic and elastic vibrations in flat-parallel-structure consisted of thin magnetic film applied on thick nonmagnetic substrate is considered. For the solution of this task the model of propagation periodic boundary regime is proposed. This solution allowed to build the amplitude-frequency characteristics of magnetic and elastic vibrations. In this case the characteristic of magnetic vibrations has the view as wide bell-like maximum on which is put by equidistance net of narrow elastic resonances which divided one to another on the frequency elastic resonance along the substrate thickness. It is executed the model presentation of superposition elastic resonances on magnetic using the system of two connected oscillators which frequencies differs in some orders. It is supposed the mechanism of superposition elastic resonances on magnetic characteristic which consist of coincidence wave phase after two-path wave passage through the substrate thickness and phase of initial excitation. It is investigated the influence of elastic wave dissipation on the structure of amplitude-frequency characteristics of magnetization and elastic displacement. It is found the critical value of elastic dissipation parameter. It is shown that below of this value the elastic vibrations have resonance character and higher become non-periodical. It is found the inversion value of dissipation parameter which determined the transition from symmetrical distribution of elastic resonances on magnetic characteristic to anti-symmetrical. It is shown that the inversion value of dissipation parameter more (on two-three orders) smaller that critical value. It is found the phenomenon of second elastic resonance which is consist of exceeding frequency maximum rounding of elastic resonance net over the frequency of maximum magnetization characteristic. It is found the connected with dissipation second resonance splitting which take place near the neighbouring of inversion value dissipation parameter.

Electromagnetic wave passage through impedance-matched graded interfaces between RHM and LHM media: passive and active transition layer variants.

We suggest two new, to the best of our knowledge, models of a flat-layered medium with variable electric permittivity and magnetic permeability. They represent a smooth transition from an ordinary medium with positive parameters to a medium with negative ones. An analytical solution to the problem of transition of a plane electromagnetic wave through such media, which describes the phenomenon of negative refraction is obtained. The resonant excitation effect is observed in the case of the medium with an active transition layer.

О моделировании гидродинамического режима течений в системах речных русел в период прохождения волны половодья на примере участка р. Оби

Рассмотрен пример численного моделирования прохождения волны половодья на участке верхней и средней Оби ниже плотины Новосибирской ГЭС. Расчеты выполнены с использованием численной модели для описания распространения и трансформации волн половодий и паводков в системе русел (STREAM), разрабо танной в ИВЭП СО РАН. Модель основана на одномерных уравнениях Сен-Венана. Система русел моделируется в виде графа типа дерево, в вершинах которого за даются условия сопряжения основных гидродинамических параметров. Приведена приближенная численная оценка порядка точности метода решения. Результаты моделирования хорошо согласуются c данными наблюдений. The goal of the study is to analyze the possibility of using the numerical model STREAM for performing research on the passage of a flood wave in a system of channels. The model was developed at IWEP SB RAS on the basis of one-dimensional Saint-Venant equations. It allows describing the flow regimes in channels, represented as a directed graph of the tree type. In the nodes of the graph (channel gates), the conjugation conditions for the main hydrodynamic parameters flow rates and water levels are set. The finite difference method is used to solve the system of equations. The difference scheme has a second order of accuracy in space and a first order in time. An approximate numerical estimate of the order of accuracy of the model using the Runge method is obtained. Numerical simulation of the Ob river section under the conditions of a high-water year 2014 has been carried out. To construct the morphometric model of the graph, data from the pilot map of the river and data of the expedition studies of IWEP SB RAS were used. The hydrological information is taken from the open access source “Automated information System of State monitoring of water bodies”. As a simulated object, a section of the Ob river from the Novosibirsk hydroelectric power station to Alexandrovskoye village is taken. The length of the site is 1210 km. The flow rates of six tributaries are taken into account. The graph consists of 12 segments. In the closing section, a boundary condition is set for water flow in the form of a flow rate versus level. To estimate the influence of the boundary condition on the simulation results, two water flow curves were constructed according to the data of 2013 and 2014 years. Qualitative and quantitative estimates of the difference in levels using two different curves, as well as comparison with the measurement data, were obtained. It is shown that the calculation method provides an acceptable agreement between the calculated values of water levels and the observational data. The possibility of using the water flow curve according to the data of the previous year as a boundary condition in the closing gate is demonstrated.

Numerical simulation of tsunami in the system of sevastopol bays

Within the framework of numerical simulation, a study was made of the penetration of tsunami waves into the system of Sevastopol bays. The non-linear SWASH hydrodynamic model was used to simulate the tsunami propagation. To determine the boundary conditions on the liquid boundary of the computational domain, using the Black Sea tsunami model, the level fluctuations near Sevastopol in the region of depths of 90 m were calculated during the passage of tsunami waves from three potential tsunami foci caused by underwater earthquakes of magnitude 7. It was found that in because of tsunami penetration into the bays of Sevastopol from the nearest focus, the rise in sea level in the tops of the bays could reach 1–2 m. The maximum amplitudes of level fluctuations were received in Pesochnaya and Karantinnaya bays, where they reached 2 m. In the Sevastopol Bay, the level rises were about 0.5–1 m. The most intense fluctuations were observed in the first 3–3.5 hours of the tsunami action. It is shown that the coastal zone of Sevastopol is protected from waves coming from distant foci by Cape Сhersones. Numerical experiments have shown that the protective piers at the entrance to the Sevastopol Bay do not have a significant effect on the sea level fluctuations caused by the tsunami inside the bay.

Seismic control of a long-span triple-tower suspension bridge using hysteretic steel damper

The seismic performance of a long-span triple-tower suspension bridge is a critical consideration in engineering communities. To promote a better seismic design, this paper presents a parametric study on the structural seismic control using hysteretic steel dampers. The finite element model is firstly established, and an introduction to the mechanical properties of the E-shaped hysteretic steel damper is made. Then, a seismic analysis is conducted under uniform earthquake excitations. Considering the effect of wave passage, the performance of hysteretic steel dampers in seismic control is further analyzed. The results indicate that the travelling wave effect greatly affects seismic responses. Increasing the damper elastic stiffness can effectively reduce the relative displacement between the main girder and either the left or the central tower. This treatment is effective for the right tower only when the wave velocity is among 400–1600 m/s, while it makes little contribution in other ranges. At an arbitrary wave velocity, increasing the damper elastic stiffness would cause minor changes to the shear forces of side towers, while its influence on the central tower is significant. A reasonable damper design for the long-span triple-tower suspension bridge depends on an essential prior evaluation of the wave velocity based on soil conditions.

Alkali ionic state behavior in γ-Irradiated borate glasses for medical ultrasonic transducer fabrication

Lenses could be added to ultrasonic transducers used in medical applications to improve them. They may solve some limiting factors, like the acoustic impedance mismatch between the transducer and the tissues, the wave collimation difficulty, the wave scattering, etc. Novel ultrasonic transducers were developed that contained lenses made from new glass systems. Al2O3, MgO, and Li2O alkali-borate glass systems were prepared via the melt-quenching technique. Structural, electrical, and ultrasonic measurements were done with regard to the effect of gamma radiation. The XRD pattern showed the glassy, amorphous nature of the lenses. FTIR absorption spectra revealed the large stability of the main structural units of borate. Electron spin resonance (ESR) spectra clarified the low distortions caused by irradiation with g-values ∼ 2.025–2.026 and recognized the formation of oxygen hole centers (OHC) caused by breaking B–O connectivity. Al ions produced the most compact glass network, resulting in the highest ultrasonic velocity and wave passage. The characteristics of transducers with and without the lens were measured. The transducers with Al2O3 lenses demonstrated the lowest signal-to-noise ratio, the greatest beam diameter, and the highest sensitivity. The results ensured the effectiveness of the prepared glass as a lens in high-frequency ultrasonic transducers that are mainly used in medical applications.

Reflection of the Electromagnetic Wave from the Region of Electron Cyclotron Absorption in Thermonuclear Plasma

A new approach to the problem of the passage of the extraordinary wave through the region of the electron–cyclotron resonance in inhomogeneous plasma was considered in the framework of the full set of Maxwell’s equations, taking into account the effects of spatial dispersion and resonance dissipation. For the model one-dimensional geometry, field distributions were calculated in the vicinity of the cyclotron resonance at the second harmonic for the normal incidence of the extraordinary wave and the reflection, transmission, and absorption coefficients were found depending on the parameters of the resonance region. As a result, the fine effect of the reflection of electromagnetic radiation from the cyclotron resonance region in transparent plasma was described and the results were compared with the observations of this effect in the experiments on the microwave heating of the plasma at the L-2M stellarator.

Reflection of the Electromagnetic Wave from the Region of Electron Cyclotron Absorption in Thermonuclear Plasma

A new approach to the problem of the passage of the extraordinary wave through the region of the electron–cyclotron resonance in inhomogeneous plasma was considered in the framework of the full set of Maxwell’s equations, taking into account the effects of spatial dispersion and resonance dissipation. For the model one-dimensional geometry, field distributions were calculated in the vicinity of the cyclotron resonance at the second harmonic for the normal incidence of the extraordinary wave and the reflection, transmission, and absorption coefficients were found depending on the parameters of the resonance region. As a result, the fine effect of the reflection of electromagnetic radiation from the cyclotron resonance region in transparent plasma was described and the results were compared with the observations of this effect in the experiments on the microwave heating of the plasma at the L-2M stellarator.

Sensitivity of an optical feedback interferometer for acoustic waves measurements.

This work presents a sensitivity study on the use of an optical feedback interferometer to measure acoustic pressure from plane waves. The sensitivity is established by linearising the interferometer's governing equations. It is shown to be independent of the acoustic wave frequency but dependent on configuration parameters such as the optical feedback parameter or the length of the laser through which the acoustic wave passes. Experimental validation is carried out using three acoustic waveguides in the 0.5-18 kHz range. The sensitivity obtained enables broadband acoustic pressure measure with a low mean relative error in comparison with a reference condenser microphone.

PROPAGATION OF MECHANIC WAVE IN TWO-DIMENSION STRATIFIED MEDIUM

The principle of emergence encourages us to look for new properties in future materials as a result of structuring of constituent elements, and mostly we are talking about non-obvious structuring. For example, understanding and simulating isotropy is on the way to robustness against internal vibrations. Structurality itself is a characteristic feature of the world around a person (protein molecules, crystal lattices, etc.). However, the variety of natural structures is so numerous that directly studying them to identify new properties appears to be quite a difficult task. Therefore, to a certain extent, the principle of emergence supposedly contrasts the need to copy or imitate natural structures with the ability to carry out inventions. Just as a wide variety of patterns are formed in an optical kaleidoscope thanks to 2 or 3 optical elements, the principle of emergence gives reason to expect that as a result of structuring only a few components of the future environment, new properties can be obtained. The development of technology, in particular, 3D printing, opens up opportunities to look at the methodology of structuring the environment in a new way. If, in addition, this process is relatively economic, then empirically, by carrying out structuring, it is possible to obtain experimental laboratory samples. Today they are talking about the possibility of achieving such effects as lensing of mechanical waves precisely thanks to emergent properties. The corresponding devices promise to find application, for example, in ultrasound diagnostics in medicine (Assoc. Prof. J. Memoli, University of Sussex, UK). The paper considers the problem of the propagation of mechanical waves in a folding periodic two-layer medium - a flat model. For such a medium, a wave equation is written and solved by the method of separation of variables. Such an equation turns out to be a linear differential equation with periodic piecewise-stable coefficients. From the basic theory of differential equations with periodic coefficients (Floquet theory), the method of transfer matrices (a method for calculating the passage of waves through multilayer media) is well known, which makes it possible to obtain a composite condition for the solvability of the wave equation. The work develops an approach to obtaining solvability conditions (constructing a dispersion equation) along with the classical method of transfer matrices. The proposed approach is in a certain sense equivalent to the transfer matrix method, however, it has some remarkable differences, in particular, it provides a rigorous mathematical basis for the transition to media with a finite number of layers.

High-altitude characterization of the Hunga pressure wave with cosmic rays by the HAWC observatory

High-energy cosmic rays that hit the Earth can be used to study large-scale atmospheric perturbations. After a first interaction in the upper parts of the atmosphere, cosmic rays produce a shower of particles that sample it down to the detector level. The HAWC (High-Altitude Water Cherenkov) gamma-ray observatory in Central Mexico at 4,100 m elevation detects air shower particles continuously with 300 water Cherenkov detectors with an active area of 12,500 m2. On January 15th, 2022, HAWC detected the passage of the pressure wave created by the explosion of the Hunga volcano in the Tonga islands, 9,000 km away, as an anomaly in the measured rate of shower particles. The HAWC measurements are used to determine the propagation speed of four pressure wave passages, and correlate the variations of the shower particle rates with the barometric pressure changes. The profile of the shower particle rate and atmospheric pressure variations for the first transit of the pressure wave at HAWC is compared to the pressure measurements at the Tonga island, near the volcanic explosion. By using the cosmic-ray propagation in the atmosphere as a probe for the pressure, it is possible to achieve very high time-resolution measurements. Moreover, the high-altitude data from HAWC allows to observe the shape of the pressure anomaly with less perturbations compared to sea level detectors. Given the particular location and the detection method of HAWC, our high-altitude data provides valuable information that contributes to fully characterize this once-in-a-century phenomenon.

X-RAY ASSESSMENT OF JAW BONE TISSUE IN PATIENTS WITH SYSTEMIC OSTEOPOROSIS BEFORE THE SURGICAL STAGE OF DENTAL IMPLANTATION

The assessment of the initial state of bone tissue is important not only for the placement of implants in accordance with the chosen treatment plan, but also for predicting the results of their osseointegration. Until recently, systemic connective tissue diseases were a contraindication to implantation, although it is believed that osseointegrated contact between the surface of an unloaded implant and the surrounding bone tissue is also possible in the case of osteoporosis. However, the effectiveness of implantation in such cases is highly questionable, because with a decrease in the mineral density of bone tissue and changes in its metabolism, there is often an increase in destruction processes, which leads to pathological bone remodeling.
 The aim of the study – to conduct a comparative analysis of the condition, structure and mineral density of jaw bone tissue in patients with systemic osteoporosis, depending on the sex, before the surgical stage of dental implantation.
 Materials and Methods. The condition, structure and density of bone tissue before the surgical stage of dental implantation were determined in 87 patients who needed dental implantation. Orthopantomograms were used to analyze the state of bone tissue in the areas where the operation was planned, for which the type of bone quality was determined according to the C.E. Misch classification. To evaluate the structure and density of bone tissue, patients were examined using spiral computed tomography (SCR) on a Picker PQ 2.00 computed tomograph (Picker International Ink., USA). When processing the information from the CT studies, the image data were studied in different planes (to determine the width and height of the alveolar ridge), and the bone density was determined by the Hansfield scale. To assess the state of bone tissue, ultrasonic densitometry was performed using an Omnisense 7000S apparatus (Sunlight Medical, Israel).
 Results and Discussion. In women with osteoporosis of group I, the radiological characteristics of the bone in the areas of future dental implantation in 36,84% and 34,20% corresponded to bone type D3 and D4, respectively. In men with osteoporosis of group II, bone type D1 prevailed (28,57% of patients) and D2 – 33,33% of patients, as well as in subjects of group III without osteoporosis, in whom the frequency of bone type D1 was visualized in 53,57% of patients and D2 in 28,57% of patients, in the absence of bone type D4. Densitometric studies revealed a decrease in the width and height of the alveolar spines in patients with systemic osteoporosis, with a prevalence of this trend in women of group I. At the same time, the passage of an ultrasound wave along the mandible was significantly lower in patients with osteoporosis compared to those without BMD disorders: 1,9 times in women and 1,3 times in men, p,p1<0.01.
 Conclusions. Thus, metabolic disorders in systemic osteoporosis adversely affect the structures of the oral cavity, especially in women, which may be the reason for the low effectiveness of dental implants and indicate the need to improve orthopedic and surgical treatment by developing adequate osteotropic treatment.

Passage of an electromagnetic wave through a rectangular waveguide with a section of a semiconductor film

Background. In microwave technology, of great interest is the creation of amplifiers and generators based on thin-layered longitudinal inhomogeneities in rectangular waveguides, which are an integral part of many functional devices in the microwave and EHF ranges. Aim. Therefore, it is of practical interest to calculate one of these inhomogeneities in a rectangular waveguide. Methods. One of the methods for calculating such structures is the diffraction of an electromagnetic wave by a segment of a semiconductor film with negative differential conductivity on a narrow wall of a rectangular waveguide. Based on the boundary conditions, a singular integral equation for the electric component of the electromagnetic field was obtained. By the method of inversion of the integral equation and by means of expansion in terms of Chebyshev polynomials, the integral equation is given in a system of two algebraic equations. The coefficients of the system are calculated according to the theory of residues. Then an equation was obtained for calculating the transmission coefficient, which was calculated in the Matcad environment. Results. Based on the integral equation, the values for calculating the transmission coefficient for the structure under consideration are obtained. Conclusion. From the graphs obtained for the calculated transmission coefficient, it can be concluded that there are frequency zones where an electromagnetic wave is amplified in the structure. So, on the basis of the structure under consideration, it is possible to create amplifiers and generators of the microwave and EHF ranges.

Inertial effects in sedimenting suspensions of solid spheres in a liquid

Particle-resolved Direct Numerical Simulations have been performed on the gravitational settling of mono-disperse solid spheres in a viscous fluid and triply periodic domain. In a comprehensive study, the bulk solid volume concentration was varied from ϕ=0.5 to 30%. To study the effect of inertia, three different Galileo numbers were considered in the inertial regime, Ga=144, 178 and 210, for which a single settling sphere exhibits distinctly different wake and path characteristics. The particle/fluid mass density ratio was fixed at 1.5. We find that for ϕ=2−30% the suspension microstructure and dynamics depend predominantly on the bulk concentration. In qualitative agreement with previous studies in literature, three different sedimentation regimes can be distinguished: (1) the dilute concentration regime for ϕ≲2% with preferential settling of particles in vertical trains, (2) the moderate concentration regime for 2%≲ϕ≲10% with preferential settling of particles in horizontal pairs with an interparticle distance of ∼ 1.5 particle diameters, and (3) the dense concentration regime for ϕ≳10% with a nearly random (“hard-sphere”) distribution of the particles in space. The clustering of particles is dictated by, respectively, trapping of particles in the wake of other particles, a drafting–kissing–tumbling (DKT) instability by which two vertically aligned particles quickly reorient themselves into a horizontally aligned particle pair, and short-range multiparticle interactions through viscous lubrication and to a lesser extent collisions between particles. In all cases, hindered settling at a reduced speed is observed as compared to a single settling sphere. The well-known Richardson–Zaki relation for the mean sedimentation velocity appears valid only for the dense concentration regime. We provide ample evidence that in the dense regime the characteristic velocity and time scales of particle motion are proportional to gDp and Dp/g, respectively, with g the gravitational acceleration and Dp the particle diameter. We also observe an ω−3 scaling of the particle velocity spectra for ωDp/g≳0.4 and we propose a model to explain this scaling behavior, based on the inertial response of the particles to small-scale flow perturbations. Kinematic waves, i.e., vertically propagating plane waves in the local concentration field, are observed in all cases, though unrelated particle motions are responsible for significant loss of the spatio-temporal coherence of the waves. The wave speed was determined from repeated space–time autocorrelations of the local concentration field and appears in reasonable agreement with Kynch sedimentation theory using the Richardson–Zaki relation. The passage of kinematic waves causes perturbations in the particle velocity at a frequency that matches well with peak frequencies in the particle velocity spectra for concentrations up to ϕ≈10%. The time-lagged cross-correlation of the vertical and horizontal particle velocity suggests that kinematic waves may trigger DKT instabilities, while conversely DKT instabilities may be responsible for the onset of kinematic waves. Finally, we suggest that obstruction and perturbation of the particle wake by neighboring particles could offer an explanation for the small influence of the Galileo number on the suspension behavior for ϕ=2−30%.

Characteristics of changes in microstructure and mechanical characteristics under high energy load

Purpose. Verification of the hypothesis about the possibility of obtaining a fine-grained structure of a metal as a result of processing with high-density energies. The methods. The research was carried out on cylindrical samples with a diameter of 50 mm and a length of 300 mm, which were made of structural steel 45 in a normalized state. The thickness of the inner coaxial layer BP1 with a detonation speed D=7.5 km/s was 3 mm, the thickness of the outer layer BP2 with a detonation speed D=3.5 km/s was 40 mm. The two-layer BP charge used in the experiment increases the duration of the shock wave and at the same time protects the samples from destruction. Findings. The mechanism of nanostructuring, in general terms, consists in the accumulation of the degree of deformation without destruction, which leads to the defragmentation of the structure with a significant increase in the density of dislocations. One of the methods that allows you to achieve a high density of dislocations, comparable to IPD, is treatment with shock waves. The change in the grain structure in the places of the pores indicates extremely high degrees of inhomogeneous deformation in these areas. During the passage of the shock wave in the middle of the sample, at the boundaries of the interface of phases with different densities, diffraction wave effects occur, which lead to the occurrence of shear deformations. It can be assumed that in the area of pores and microcracks, the deformation conditions are similar to those realized by some methods of intensive plastic deformation. This leads to a sharp grinding of the grain structure and a corresponding change in mechanical properties. The originality. The paper found that the processing of steel parts with the help of high-density energy leads to a sharp grinding of the grain to the nanostructure size and, as a result, to an increase in mechanical properties. The revealed regularities make it possible to obtain optimal parameters of high-energy processing, which lead to an increase in hardness, a redistribution of internal stresses and a decrease in surface roughness. Practical implementation. Obtaining grains with nanostructural characteristics in the structure of the material will allow to create fundamentally new devices and materials. Such materials will have properties significantly exceeding their achieved level – which is important for many fields of engineering, medicine, biotechnology, environmental protection, defense, etc.

Визуализация тепловых потоков в высокоскоростном течении за ударной волной

The paper presents the thermographic studies of unsteady heat fluxes behind a plane shock wave in the rectangular 24x48 mm shock tube test section. Consecutive panoramic visualization of the heat fluxes plots on streamlined walls after the plane shock wave interaction with a rectangular obstacle fixed on the channel wall are obtained. The duration of the recorded thermal processes is up to 40 milliseconds after the shock wave passage. The heating and cooling of the test chamber walls streamlined by supersonic flow are visualized using the Telops FAST M200 high-speed infrared camera (operating range 1.5 – 5.1 microns) through the quartz windows transparent to infrared radiation. Visualization of the thermal fields were compared with the shadow images and results of 2D numerical simulation of a nonstationary gas dynamic process after the diffraction of a shock wave with Mach numbers M=2.0-4.5.