Shock Waves In Air Research Articles

Computational–Experimental Study of the Liquid Drop Fragmentation Caused by an Air Shock Wave

Computational–Experimental Study of the Liquid Drop Fragmentation Caused by an Air Shock Wave

Оцінка наслідків застосування тактичної ядерної зброї на населення та інфраструктуру в районах ядерного вибуху

The article analyzes the process of formation and establishes the characteristics of the striking factors of a nuclear explosion of tactical nuclear ammunition with a power of 0.1 to 10 kt when damaging military facilities and the accompanying damage to the population of civilian communities and personnel of infrastructure facilities. Calculated are data on the parameters of air shock wave action zones, penetrating radiation flow, light pulse energy beam flow, and the dimensions of the zone of radioactive contamination of the area, which can create a negative impact on the population, residential buildings, personnel, and critical infrastructure facilities in the area of application of tactical nuclear weapons. It is shown that the zone affected by an air shock wave, depending on the type of explosion of tactical nuclear ammunition and its power, can reach a radius of up to 3100 m. Dangerous light pulse damage to the population and personnel located in the open area will be observed at a distance of 440 to 3700 m from the epicenter of the nuclear explosion. The negative impact of the penetrating radiation of a nuclear explosion on the population and personnel of critical infrastructure facilities will be observed at distances from 560 to 1300 m, depending on the type of explosion and the power of the tactical nuclear ammunition. The dimensions of the zone of radioactive contamination, in the case of the explosion of tactical nuclear ammunition, in which the most severe degree of radiation damage to the population and personnel of critical infrastructure objects will be observed, with their open location in the area, depending on the power and type of explosion, can reach from 1400 to 2600 m. And the zone in which it is necessary to carry out the priority immediate evacuation of the population can be from 3.4 to 44.0 km in the direction of the average wind. It was determined that the scale of radioactive contamination of the area will have the greatest values of the size of the areas of negative impact relative to other types of impressive factors of the nuclear explosion of tactical nuclear ammunition. In large areas of the regions adjacent to the area of application of the specified ammunition, a significant negative radiation effect will be created, which will require measures of radiation protection and evacuation of the population.

Single-shot ultrafast dual-view imaging of shock waves in parallel laser processing

Single-shot ultrafast optical imaging has revealed various non-repetitive processes, but it has conventionally provided only single-view measurements. Here, we demonstrate a single-shot ultrafast dual-view imaging technique by monitoring shock waves in laser processing of glass using single or parallelized excitation pulses. We visualize the spatiotemporal evolution of shock waves in air at 0.5 Gfps with five frames in both top and side views, indicating the velocity anisotropy and interaction of shock waves. Our technique can contribute to a comprehensive understanding not only of shock wave dynamics but also of other spatially complex ultrafast phenomena including laser-induced plasma and electrical discharge.

Оценка изменения безопасных расстояний при нарушениях регламента испытаний газопроводов

Accidents occurring during the process of gas pipelines testing are characterized by the impossibility of the occurrence of thermal radiation of jet flames and fire in the pit-damaging factors dominating the operation stage of the facility. In addition, what is happening cannot be accompanied by the baric effect of chemical explosions. However, taking into account the significant increase in pressure in the gas pipeline during pneumatic tests, such damaging factors of the accident as the scattering of fragments, the pressure effect of a high-speed jet and the baric effect of the primary shock wave are amplified. The issue of ensuring the safety of personnel present near the test site becomes relevant. As a result, the need occurs to determine precisely the safe distances to the gas pipeline. Protective zones for the population are also established based on the identified safe distances. Within the framework of the risk-oriented approach, the procedure for determining safe distances is reduced to calculating the distances at which damaging factors lose their damaging properties. When assigning protective zones, it is required to consider the possibility of changing the indicator under consideration, due to probable errors of personnel in the preparation and conduct of tests. Even non-critical miscalculations can significantly affect the determination of a safe distance. The article presents an assessment of the relative values of safe distances, taking into account possible violations of the regulations regarding backfilling and filling with water or air, during hydraulic or pneumatic tests of gas pipelines. Relative values of safe distances are also established in terms of the scattering of fragments and the impact of an air shock wave of a physical explosion on people and building objects.

Обоснование безопасных расстояний по отношению к окружающим объектам при проведении камуфлетных взрывов в горных породах

Introduction. Despite the simplicity and accessibility of camouflage blasting, the issues of ensuring the safe conduct of such work are important. A camouflage explosion eliminates the occurrence of an air shock wave and the harmful effects of the explosion products on the environment, but leads to strong seismic vibrations. The impact of seismic loads on nearby objects can lead to the loss of their carrying capacity, damage and destruction, therefore, when choosing a place for installing camouflage charges, the task arises of assessing the field of environmental velocities during an explosion and determining the distances at which the velocities do not exceed the maximum allowable values established for objects under consideration. The aim of the study is to solve the problem of determining the velocity field in a continuous elastic-plastic medium during a camouflage explosion. Research methodology. The solution of the central symmetric problem of the propagation of explosive disturbances in solid media is based on the assumption that a deep spherical charge of a certain radius is placed in an unbounded half-space, which instantly turns into a high-pressure gas without changing the volume. It is assumed that the pressure in the cavity decreases according to a power law, and the relationship of pressure with the radius, velocity and acceleration of the expanding cavity is determined by the camouflage equation , whose constants A, B and C are functions of the parameters of rocks and soils. The perturbed state of the medium caused by the expanding cavity is also characterized by densities ρ0 and ρ respectively, in the elastic and plastic regions of its deformation, and the transition from the elastic state to the plastic state is accompanied by an instantaneous change in the density of the medium from ρ0 to ρ, introduced to approximately take into account the actual compressibility. Results. The determination of the velocity field in the medium surrounding the charge during the explosion is reduced to solving the ordinary differential equation of motion of a spherical cavity expanding due to internal pressure. It is shown that the unknown constant included in the obtained relation can be determined from the condition of conservation of the energy released during the explosion in the entire elastoplastic region of the medium motion. Discussion. The novelty of the result obtained lies in the substantiation of the possibility of using the assumptions about the vibrationless nature of the movement of the camouflage cavity and the incompressibility of the medium in the plastic and elastic regions to determine the velocity field that forms in a continuous medium during the explosion of a camouflage charge. Conclusion. Under the assumption of the vibrationless nature of the motion and the incompressibility of the medium in the plastic and elastic regions, a solution is obtained for the centrally symmetric problem of determining the velocity field in a continuous elastoplastic medium during a camouflage explosion. The solution obtained makes it possible to estimate the sizes of expansion zones, plastic deformation of the medium, and the impact of explosive disturbances on various objects.

Adjustment of basement rooms of buildings for shelter for the civilian population

A feature of the russia's war against Ukraine is the huge number of casualties among the civilian population in the first months of the war.
 The insufficient number of protective structures (storages, anti-radiation shelters, dual-purpose structures), their technical condition and availability, as well as recommendations for sheltering the population in the simplest shelters – basements of residential buildings – lead to mass casualties among the civilian population.
 The definition of the term "simplest shelter" does not provide for the protection of the population from the effects of the means of destruction, but only the reduction of their effects. According to the definition of regulatory documents, only a part (more or less than half of its height) of basement and basement premises is located below the surface of the ground and, accordingly, these premises are as vulnerable as the above-ground floors.
 Normative documents on the protection of the civilian population, which became the basis of the state building regulations of Ukraine in 1997, were developed in the middle of the 20th century, and the changes that were made in 25 years did not change the parameters and equipment of protective structures.
 The main goal of the study is to development of measures that provide an opportunity to ensure full protection of the civilian population not involved in the work of critical infrastructure.
 The set goal outlined a list of research tasks, namely, reducing the number of victims among the civilian population by adapting the existing basements of multi-story buildings for shelter to protect the population from the effects of conventional means of destruction and the side effects of modern weapons of mass destruction (chemical); fragments of destroyed building structures; of an air shock wave with an estimated excess pressure of not less than ∆Pф =20 kPa (0.2 kg/cm²)
 Specialists of the "Renaissance" NGO proposed project solutions for creating shelters in the basements of existing residential buildings by strengthening the structures enclosing the basements.
 The listed measures enable the residents of houses living in cities on the territory controlled by Ukraine, but under constant rocket fire, to stay in their houses and rest at night in a protected space.

CURRENT STATUS AND PROPOSALS REGARDING THE PROTECTION OF THE CIVILIAN POPULATION

The Code of Civil Protection of Ukraine is the main legislative document regulating measures for the protection of civilians. A number of normative documents were created to protect the population from the action of conventional means of destruction, air shock wave, in accordance with the requirements of the legislation. The current legislation and building codes on technical measures of civil protection did not provide for the realities of war, did not take into account the needs of people with limited mobility. For the second year, the war continues, people are dying, and the leadership of the State Emergency Service sees no problems in protecting civilians and has no desire to change the existing imperfect civil protection system. The overwhelming number of current shelters and anti-radiation shelters was built in Soviet times and according to Soviet standards. Today, buildings meet the requirements of the mid-20th century for protective properties, but do not at all meet the modern requirements and realities of war. In particular, the estimated capacity of storages and anti-radiation shelters does not correspond to the anthropological parameters of modern man, including the less mobile population groups. An analysis of the regulatory documentation of the countries of the world showed that the capacity indicators specified in the standards are most likely an error that occurred several decades ago and has been repeated during this time. We analyzed the possibility of using shelters facilities in accordance with the planning of benches and beds according to the recommendations of the State Emergency Service. We proposed the necessary parameters or placing for placing rows of benches and beds in shelters and anti-radiation shelters. The given examples show that using existing shelters cannot be acceptable according to the State Emergency Services standards and recommendations.However, after carrying out a set of measures for the reconstruction and refurbishment of these buildings, these premises can be used as temporary structures to protect the population.

Dynamics of spatially confined ns laser induced atmospheric air plasma and shock waves: visualization vis-à-vis validation

A clear visualization of the physical processes of spatially confined ns laser induced atmospheric air plasma within a rectangular glass cavity using optical imaging is presented. The occurrence of various processes starting from the early plasma and shock wave expansion dynamics to shock reflection at the cavity boundaries and compression of the plasma due to reflected shockwaves is studied using defocused shadowgraphy and self-emission imaging techniques. Experimentally, we evidenced that the counter propagating reflected primary shockwaves interact with the expanding plasma generating a secondary shockwave which compresses the plasma core, modifying the plasma morphology resulting in enhanced plasma parameters. The numerical simulations performed via the two-dimensional hydrodynamic (2D-HD) FLASH codes, revealed that the number density increases up to a maximum of 3.6 times compared to the unconfined plasma. The input laser pulse energy and the aspect ratio of the cavity is observed to play a dominant role in the confinement and compression of the plasma.

Learning ability and spatial memory status in rats during the acute period of mild blast-induced traumatic brain injury

The mild blast-induced brain traumatic injury like a battle fatigue, leads to neurological disability, including due to a violation of spatial memory. The presented work is the result of a blast-induced brain traumatic injury study on a self-developed device. For the experiment, 15 white Wistar rats were used and were divided into 3 groups: rats of Experimental group exposed by air shock wave (26–36 кPа); Sham group (anesthesia with halothane and fixation in a horizontal position) and Intact group. The ability to learning (food reinforcement) and the spatial memory state (time to search for food, vertical locomotor activity) were studied in the complex maze during the first 5 days of the posttraumatic period. To assess the emotional state, we counted the number and observed the quality of grooming acts. All researches were conducted in compliance with modern standards for humane attitude of animals. The results of our study clearly indicate a violation of spatial memory, which was manifested in the time of searching lengthening of the feeder and in the increase of vertical locomotor activity in the rats of the experimental group, while the animals clearly remembered that they were looking for food. The analysis of grooming showed qualitative changes in the form of incomplete and prolonged acts. Such changes indicate the development of anxiety in rats with mild blast-induced traumatic brain injury. This, in turn, led to deterioration of the spatial orientation and memory formation. Thus, the consequence of a mild blast-induced traumatic brain injury in the acute period is changes in the cognitive function of the brain in the form of deterioration of spatial memory, which was aggravated by a disturbance of emotionality in the form of anxiety. At the same time, the memory regarding the presence of food was formed adequately. Keywords: explosion, central nervous system, cognitive function, memory, maze.

Experimental study on the elastic-plastic dynamic response of shallow-buried corrugated steel-plain concrete composite structures under long-duration plane blast wave loading

To study the elastic-plastic dynamic response characteristics of shallow-buried corrugated steel-plain concrete (CSPC) composite structures under long-duration plane blast loads, a series of tests were conducted in a large confined blast-resistant test facility using the plane charge explosion technique (PCET), and the dynamic response and deformation laws of CSPC arches, reinforced concrete (RC) arches and plain concrete (PC) arches under different blast loads were comprehensively compared and analyzed. The test results show that under this test condition, the plane air shock wave overpressure peak with the increase in charge is basically a linear growth, but the shock wave pressure duration of action and impulse growth rate gradually decreased, the test device simulated by the explosion shock wave pressure duration of the maximum action time of more than 340 ms. Comparing the differences in the dynamic response of the three structures, it was found that when the peak long-duration shock wave overpressure acting on the structure reached 0.09 MPa, the PC model had plastic deformation, and the combined reinforced concrete and CSPC structure exhibited fully elastic deformation. When the peak shock wave overpressure reaches 0.238 MPa, the RC model begins to show plastic deformation. When the peak shock wave overpressure increased to 0.315 MPa, all models produced significant plastic deformation. The deformation resilience of the CSPC composite structure under the above-mentioned blast shock wave load is greater than that of RC and PC structures, which have good deformation recovery ability and can effectively reduce the damage to the structure by blast shock. On the contrary, the peak structural vibration acceleration caused by the blast shock wave is greater in the CSPC combined structure than in the RC and PC structure, and the deformation rebound and oscillation of the corrugated steel plate is the main way of impact energy dissipation. The results of the study provide an experimental basis for the simulation of long-duration plane blast waves and the optimal design of CSPC blast-resistant structures.

Numerical Simulations of Air Shock Wave Overpressure Propagation in Shallow-buried Explosion

Shallow-buried explosion is a typical working condition of ammunition. Studying the overpressure propagation law of air shock wave in shallow-buried explosion is helpful to completely characterize the ammunition power in actual combat. In this paper, a numerical model of shallow-buried explosion of cylindrical charge based on Euler method is established in the framework of simulation software AUTODYN, which simulates the formation process of crater when cylindrical charge is initiated under the conditions of different charge amount and different buried depth, and analyzes the propagation law of explosion shock wave in the air. The following conclusions are drawn: compared with the mass of charge, the depth of burial has more influence on the surface air shock wave. According to the simulation data, the empirical formulas related to the peak overpressure of shock wave and the charge, buried depth and horizontal detonation center distance are fitted.

Interferometric measurements of laser-induced shockwaves in air: Variable laser energy

When focused to a small spot size in air, a sufficiently energetic laser pulse initiates a rapidly expanding plasma. After a delay, a shockwave detaches from the plasma boundary and propagates. General features of the shockwaves can be deduced from condenser microphone measurements. However, the minimum range is limited by damage thresholds, and the presence of the microphone introduces a number of measurement artifacts. Distortion of the signal is caused by diffraction around the sensor, and the limited bandwidth does not allow rise times to be correctly quantified. In contrast, optical interferometry is a nonintrusive diagnostic for quantifying shockwave characteristics. In this study, a Nd:YAG laser is focused through a converging lens in order to generate laser-induced shockwaves. By using a variable attenuator, four laser energy outputs are examined: 25, 50, 75, and 100% of the maximum energy transmission. Heterodyne Mach–Zehnder interferometer measurements are made from 10 mm to 200 mm from the focal point of the lens. Virtual velocity signals, proportional to the time derivative of optical phase differences, are used to estimate density and pressure time histories, along with peak pressure as a function of distance.

Оцінка рівня експресії HIF1A та паренхіматозно-стромальних відношень після травматичного впливу повітряної ударної хвилі на печінку

The purpose of the study was to investigate, analyze and evaluate the expression level of HIF1A and parenchymal-stromal relations after traumatic air shock wave exposure to the liver. Materials and methods. The material for the study was the liver of 30 male rats, weighing 177.5 ± 15.8 g. All animals were randomly divided into three groups: group 1 consisted of intact rats (n - 6), group 2 – control (halothane anesthesia with fixation) (n - 12), group 3 (n - 12) – experimental animals (halothane anesthesia with fixation, traumatic single action of an air shock wave with an excess pressure of 31.6 ± 4.8, which was generated in the device developed by us). In order to study the reactive changes in the liver after exposure to an air shock wave, an immunohistochemical method was used to study the expression of the hypoxia marker HIF1A and a morphometric analysis of parenchymal-stromal relations on the 7th and 30th day of the experiment. Results and discussion. The studied expression of the transcription factor HIF1A in the liver after exposure to an air shock wave by the immunohistochemical method showed a relationship with the consequences that occur after the injury (alteration, inflammation, regeneration), as well as with the observation period and distribution in the liver parenchyma. Despite the diffuse injury of the liver, which occurs after a low-intensity exposure to an air shock wave, we record a high threshold of resistance of liver cells to the action of this traumatic factor. The absence of HIF1A expression in the liver one month after exposure to an air shock wave is a direct indication of the restoration of the functioning of specialized liver cells, despite the initial significant diffuse changes at the level of the microcirculatory channel of the liver lobules. Research has repeatedly shown the high regenerative potential of the liver, despite the factors of influence, toxic, mechanical, and others. Understanding the spatial response of liver cells to external and internal factors will allow us to assess the adaptive capabilities of the metabolism of hepatocytes that are in different conditions of blood supply, which will expand our knowledge about the pathogenesis of the post-traumatic period and offer new therapeutic tools for their correction. Conclusion. Morphometric analysis of parenchymal-stromal relations of the liver after a single exposure to an air shock wave showed a significant decrease in the area of hepatocytes by 8% and a significant increase in the area of connective tissue by almost 2.4 times on the 30th day of the post-traumatic period in comparison with the control group of animals. Evaluation of the level of expression of the transcription factor HIF1A in the liver at the stages of the post-traumatic period showed that moderate expression was characteristic of the subcapsular area of the liver in the early post-traumatic period. On the 30th day of the post-traumatic period, the accumulation of the HIF1A marker in the liver of the experimental group of animals was not statistically significant compared to the control group

STRESS-STRAIN STATE OF SHELTER STRUCTURES UNDER THE ACTION OF AIR SHOCK WAVE

The paper considers the stress-strain state of shelter structures under the action of an air shock wave on the example of a 7-storey experimental residential building

Инженерная методика оперативного прогнозирования степеней разрушения жилых зданий при воздействии обычных средств поражения

PURPOSE. In the works previously performed by the authors it has been proposed to determine conditions for buildings destruction by the method of the stress state automated calculating their building structures after external loads redistribution as a result of “destroyed” elements removal from the design scheme. This has made it possible to determine for the first time the types and number of the buildings supporting structures elements, whose destruction leads to their collapse. In addition, the degree of building destruction is determined not by the amount of overpressure in the front of the air shock wave acting on the building, but by the amount of economic damage, based on the feasibility of its restoration, depending on the proportion of destroyed interconnected structural elements of the building. For the first time, it allows promptly predicting both the degree of individual buildings destruction and their groups in the lesion focus. METHODS. The authors have used positions of the probability theory and the apparatus of mathematical statistics, as well as methods for determining the overpressure in the front of the air shock wave under the influence of conventional destruction means. FINDINGS. As a criterion for the effectiveness of the proposed methodology for forecasting the degree of buildings destruction under the influence of conventional destruction means, the accuracy increase degree of buildings destruction level determining has been taken. A comparative calculation of the brick building destruction degree has been made. With regard to panel and monolithic buildings, it is impossible to perform comparative calculations, due to lack of data on the magnitude of overpressure in the front of the nuclear explosion air shock wave, which causes weak, medium, strong and complete destruction of residential buildings of these types. RESEARCH APPLICATION FIELD. The results can be used to forecast the volume of emergency recovery work in relation to residential buildings and areas of cities and economic facilities under the influence of conventional destruction means as well as to develop measures to ensure the stability of residential buildings functioning as a result of conventional destruction means impact. CONCLUSIONS. Scientific and methodological approaches for the operational forecasting the residential buildings destruction degree under the influence of conventional destruction means are proposed. The analysis of comparative calculations shows that the accuracy of the developed methodology application in comparison with the existing ones is increased by 50 %.

Reliability of a Built-in Underground Structure under the Impact of an Air Shock Wave

Reliability of a Built-in Underground Structure under the Impact of an Air Shock Wave

IMPROVED CRITERION IN METHOD OF ASSESSMENT OF THE SAFETY LEVEL OF THE PROCESS OF LAND RECULTIVATION OF PLACES OF AMMUNITION DISPOSAL AND DESTRUCTION

The relevance of the research and the need to develop methods that allow assessing the level of safety of the disposal and destruction of ammunition sites are shown not only at the present time, but also in the future when land reclamation measures are applied. An improved criterion for assessing the safety level of the reclamation process of the lands of the disposal and destruction of ammunition sites was developed based on the use of a regulatory approach, and significant indicators were determined, namely: the probability of an explosion, the amount of excessive pressure in the air shock wave, and the level of degradation of the lands of the disposal and destruction of ammunition sites. An improved method of assessing the safety level of the process of land reclamation of the disposal and destruction of munitions by using an improved criterion for assessing the safety level of the process has been developed. The proposed method is suitable not only for long-term evaluation, but also for operational safety management of similar objects. The main advantage of the proposed method in comparison with those used today is to take into account the entire complex of active factors of explosion risk and environmental danger, while minimizing the number of significant environmental quality indicators. Thanks to this, it becomes possible to reduce the amount of calculations required for accurate assessment by a set of regulatory criteria, and also simplifies the assessment procedure without loss of accuracy.

Experimental and numerical study on protective effect of RC blast wall against air shock wave

Prototype experiments were carried out on the explosion-proof performance of the RC blast wall. The mass of TNT detonated in the experiments is 5 kg and 20 kg respectively. The shock wave overpressure was tested in different regions. The above experiments were numerically simulated, and the simulated shock wave overpressure waveforms were compared with that tested and given by CONWEP program. The results show that the numerically simulated waveform is slightly different from the test waveform, but similar to CONWEP waveform. Through dimensional analysis and numerical simulation under different working conditions, the equation for the attenuation rate of the diffraction overpressure behind the blast wall was obtained. According to the corresponding standards, the degree of casualties and the damage degree of the brick concrete building at a certain distance behind the wall can be determined when parameters are set. The above results can provide a reference for the design and construction of the reinforced concrete blast wall.

Experimental investigation of polymer gravel slab under air contact and near-field explosions

Polymer materials are widely used in critical infrastructures, which may be damaged by explosion loads in complex service conditions. In this study, field tests are carried out to investigate damage modes and characteristics of polymer gravel slabs under air contact and near-field explosion. Eight pieces of polymer gravel slabs are subjected to air contact and near-field explosion using different quantities of explosive charge. The time-history curves of the upper and lower side explosion shock waves of the specimen are obtained by an air shock wave tester. It was found that polymer gravel slabs have a proper attenuation effect on the explosion shock waves. Also, the local punching shear perforation damage is the main damage mode under the air contact explosion. In addition, top surface exfoliating and overall bending failure occur under the air near-field explosion.

Equation of State for Bismuth at High Energy Densities

The purpose of this work is to describe the thermodynamic properties of bismuth in a broad scope of mechanical and thermal effects. A model of the equation of state in a closed form of the functional relationship between pressure, specific volume, and specific internal energy is developed. A new expression is proposed for the internal energy of a zero-temperature isotherm in a wide range of compression ratios, which has asymptotics to the Thomas–Fermi model with corrections. Based on the new model, an equation of state for bismuth in the region of body-centered cubic solid and liquid phases is constructed. The results of calculating the thermodynamic characteristics of these condensed phases with the new EOS are compared with the available experimental data for this metal in waves of shock compression and isentropic expansion. The parameters of shock waves in air obtained earlier by unloading shock-compressed bismuth samples are reconsidered. The newly developed equation of state can be used in modeling various processes in this material at high energy densities.