Impact Of Shock Wave Research Articles

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.

Research on the Rule of Explosion Shock Wave Propagation in Multi-Stage Cavity Energy-Absorbing Structures.

The propagation laws of explosion shock waves and flames in various chambers were explored through a self-built large-scale gas explosion experimental system. The propagation process of shock waves inside the cavity was explored through numerical simulation using Ansys Fluent, and an extended study was conducted on the wave attenuation effect of multiple cavities connected in a series. The findings show that the cavity's length and diameter influenced the weakening impact of shock waves and explosive flames. By creating a reverse shock wave through complicated superposition, the cavity's shock wave weakening mechanism worked. By suppressing detonation creation inside the cavity, the explosive flame was weakened by the cavity's design. The multi-stage cavity exhibited sound-weakening effects on both shock waves and explosive flames, and an expression was established for the relationship between the suppression rate of shock force and the number of cavities. Diffusion cavities 35, 55, 58, and 85 successfully suppressed explosive flames. The multi-stage cavity efficiently reduced the explosion shock wave. The flame suppression rate of the 58-35 diffusion cavity explosion was 93.38%, whereas it was 97.31% for the 58-35-55 cavity explosion. In engineering practice, employing the 58-58 cavity is advised due to the construction area, construction cost, and wave attenuation impact.

Challenges to the integrity of calandria, the CANDU PHWR moderator vessel, under serious accident loads and consequences of its failure

This paper summarizes the technical and analytical basis for a more advanced examination of structural integrity of a CANDU PHWR Calandria vessel under certain reactor accident conditions. Of foremost interest is the early Boiling Liquid Expanding Vapour Explosions (BLEVEs) induced challenge to vessel structural integrity following a spontaneous in-core rupture of a fuel channel. A sudden, flashing jet discharge of over 100 kg/s of the 10 MPa, 300 °C saturated primary coolant into its 70 °C subcooled near atmospheric pressure moderator water inventory will cause an explosive, shock wave impact. This results from rapid nucleation and vaporization of the discharged superheated liquid. Consequential pressure pulse, pipe-whip and bundle debris impact will induce damage to adjacent channels and cause widespread failure of fuel channel calandria tube rolled joints. These thin tubes inevitably deform to create serious challenges to vessel integrity. On the other extreme of reactor accidents, is the matter of an in-vessel-retention (IVR) of high temperature molten fuel debris in the reactor vessel after a severe core damage accident, such as one caused by an unmitigated station blackout. This scenario has understandably drawn greater attention after Fukushima and potential IVR in the > 200 mm thick PWR vessels when partly submerged in water is viable.It is highly unlikely that we will see reactor debris melt retention in this 19 to 29 mm thick, stepped shell with a tapestry of welds. This is because partial shell melting, diminished strength beyond 650 °C across 2/3 of the thin shell thickness and severe thermal stresses adds to underlying residual stresses near the welded seams. The result is inevitable catastrophic off-site consequences as energetic interactions upon vessel breach of water with hot debris can cause additional steam & hydrogen explosions, containment failures, and large off-site releases.This paper presents technical arguments to illustrate the problem in accepting faulty assumptions conveniently made in licensing safety assessments to simplistically claim survival of the thin-walled welded structure under these two illustrative accidents. I propose pathways to further investigations. Therefore, the issue of Calandria vessel survival under a wide range of accident conditions must be given a second, thoughtful look. Extending boundaries of a safe operating envelope as pressure tubes age needs to be avoided. We need to be more realistic in our severe accident analysis and consequence assessments. Fukushima taught us that the consequences of continuing to rely on convenient but technically faulty rationale, along with hype of eternal safety, can be very unforgiving.

Insight into the synergistic mechanism of sonolysis and sono-induced BiFeO3 nanorods piezocatalysis in atenolol degradation: Ultrasonic parameters, ROS and degradation pathways

Herein, BiFeO3 nanorods (BFO NRs) was synthesized as the piezoelectric catalyst. The synergistic mechanism of sonolysis and sono-induced BFO-piezocatalysis in atenolol degradation was revealed and the effect of ultrasonic parameters on it was investigated for the first time. The results indicated that 100 kHz was the optimal frequency for the sonolytic and sono-piezocatalytic degradation of atenolol in ultrasound/BFO nanorods (US/BFO NRs) system, with the highest synergistic coefficient of 3.43. The piezoelectric potential differences of BFO NRs by COMSOL Multiphysics simulations further distinguishing that the impact of cavitation shock wave and ultrasonic vibration from sonochemistry reaction (i.e., 2.48, −2.48 and 6.60 V versus 0.008, −0.008 and 0.02 V under tensile, compressive and shear stress at 100 kHz). The latter piezoelectric potentials were insufficient for reactive-oxygen-species (ROS) generation, while the former contributed to 53.93% •OH yield in US/BFO NRs system. Sono-piezocatalysis was found more sensitive to ultrasonic power density than sonolysis. The quenching experiments and ESR tests indicated that the ROS contribution in atenolol degradation followed the order of •OH > 1O2 > h+ > O2•- in US/BFO NRs system and 1O2 generation is exclusively dissolved-oxygen dependent. Four degradation pathways for atenolol in US/BFO NRs system were proposed via products identification and DFT calculation. Toxicity assessment by ECOSAR suggested the toxicity of the degradation products could be controlled.

Assessment of shock wave assisted crystallographic structural stability of poly-crystalline and single crystalline lithium sulfate monohydrate crystals

In the present work, we demonstrate the interesting findings of shock wave recovery experiment conducted on poly-crystalline lithium sulfate monohydrate crystals (Li2SO4.H2O) under 50 and 100 shock pulses loaded conditions and the obtained results are compared to the obtained results of single crystal Li2SO4.H2O. The poly-crystalline Li2SO4.H2O samples neither undergo any crystallographic phase transitions nor shock wave assisted dehydration. But, the attained diffraction and Raman results indicate that, at shock loaded conditions, lots of structural deformation and distortions occur in the mother crystal structure by the impact of shock waves. Also, at shocked conditions, the super-paramagnetic state of Li2SO4.H2O is significantly affected and remarkable reduction (10–1 to 10–7) of the saturation magnetization is found. Note that, in the case of single crystalline Li2SO4.H2O, the disordered crystal structure has been witnessed for shock loaded samples.

The influence of flexible/rigid obstacle on flame propagation and blast injuries risk in gas explosion

ABSTRACT The interaction between flame, shock wave and obstacle is an important content in the study of fuel combustion and safety. In this paper, the performance difference between flexible and rigid obstacles in the process of explosion flame propagation was studied. Five barriers with different blocking rates（BR） were tested in the pipeline for methane premixed explosion. The high-speed photography system collects the flame image, the flame front velocity is calculated, and the dynamic pressure changes in the upstream and downstream pipelines during flame propagation are recorded by the high-frequency pressure acquisition system. The results show that the obstacle affects the unburned flow field and generates compression waves and shear layers. The explosion promotion degree of the two obstacles presents different trends, and the peak pressure decreases. At the same time, obstacles reflect pressure waves, causing instability in the front of the flame. With the increase of plugging rate, the difference of peak pressure rises to 30% at BR = 0.4. The flame velocity of flexible obstacles is also more flat, and the peak velocity at BR = 0.2 and BR = 0.4 is close to 43 m/s. During the study, it was found that the flexible material can effectively absorb the reflected wave, and the pressure oscillation is absorbed. The average amplitude of the rigid oscillation rises from 4 kPa to 10 kPa, and the flexible oscillation decreases to nearly zero. The difference of barrier materials makes the impact of shock wave on flame and primary explosive injury (PBI) lighter, which is more conducive to assessing the explosion risk of combustible gas.

Crack Damage Propagation and Morphology Distribution of Hydraulic Electric Pulse Fractured Coal.

This work discusses the damage and failure effect of a hydraulic electric pulse and the law of crack growth on coal. The impact and failure effect of a water shock wave and the mechanism of crack initiation, propagation, and arrest were studied by numerical simulation and the fracturing test of coal, combined with CT scanning, PCAS software, and Mimics 3D reconstruction technology. The results show that a high voltage electric pulse that increases permeability is an effective artificial crack making technology. The crack spreads radially along the borehole, and the damage degree, number, and complexity were positively correlated with the discharge voltage and discharge times. The crack area, volume, damage factor, and other parameters increased steadily. The cracks in the coal first start from two symmetrical angles, and finally distribute in a 360 deg circumferential direction, forming a multiangle crack spatial network structure. The fractal dimension of the crack group increases, the number of microcracks and the roughness of the crack group increases, the overall fractal dimension of the specimen decreases, and the roughness between cracks weakens. The cracks then form a smooth coal-bed methane migration channel. The research results can provide some theoretical guidance for the evaluation of crack damage propagation and the effect of electric pulse fracturing in water.

Effect of shock wave on nucleation and droplet growth of CO2 in flue gas in supersonic separators

To reduce carbon emissions caused by fossil fuel combustion, this work evaluates a potential carbon capture method. Based on heat transfer theory, aerodynamics and condensation dynamics, a mathematical model is proposed to depict the nonequilibrium condensation of CO2 in flue gas (N2–CO2). The interaction between shock wave and non-equilibrium condensation is clarified. The results show that when the shock wave enters nucleation area, the nucleation process is rapidly terminated and droplet growth process disappears. After the shock wave, the supersaturation decreases rapidly from 2.26 to 0.19, the gas changes from supersaturated state to unsaturated state, and the system returns to the thermodynamic equilibrium state. When the shock wave appears in the droplet growth area, there is a complete nucleation process. The gas molecules in front of the shock wave form stable droplets and release latent heat, leading to the fluctuation of temperature and pressure. After the shock wave, the droplet growth environment is destroyed, resulting in droplet radius and liquid content drop to 0. Increasing CO2 content can not only reduce the impact of shock wave on flows, but also strengthen the heat and mass transfer, and obtain larger droplet radius and higher liquid content.

Problems of environmental protection as an aspect of military confrontation

One of the aspects of military conflicts is environmental. A specific and rather intense impact accompanies the conduct of hostilities and preparations for war on the environment. Although ecological damage is not usually a goal of warfare, such damage is integral to most armed conflicts. There is no single model of how war affects the environment. At the same time, war, like most human activity, changes the environment, damaging natural ecosystems and destroying human habitats. Numerous attempts to classify the environmental consequences of military confrontation boil down to the fact that it is expedient to distinguish direct and indirect implications on different scales and at various stages of military conflict. The destruction of natural systems of Ukraine during the armed aggression of the Russian Federation and the accompanying environmental challenges are numerous and diverse: the use of ammunition and damage to enterprises of various industries, including the chemical industry, the rise of radioactive dust into the air due to the movement of heavy equipment in the Chornobyl zone and strikes on nuclear power plants and associated infrastructure facilities, destruction of gas pipelines and oil storage facilities, numerous fires in populated areas, mining of large areas and the impact of shock waves and combustion products on the components of natural and anthropogenically altered ecosystems, etc. The consequences of hostilities will affect nature, people, and society even after these actions are over. Among other things, the territories and objects of the PZF are in the risk zone. It is essential to record and document the facts of environmental crimes and develop long-term plans to neutralize their consequences.

Explosion Mechanism of Lubricating Oil Droplets in High-Temperature and High-Pressure Combustion Environments

Lubricating oil-induced pre-ignition is a critical issue that requires attention in downsized gasoline engines and marine low-speed two-stroke natural gas engines. As a result, the ignition behavior of lubricating oil at high temperatures and pressures has been extensively studied. In some cases, when studying the ignition of oil droplets using a rapid compression machine, an explosion-like behavior of the oil droplets is observed, producing a soot cloud that can spread throughout the combustion chamber, especially when the ignition delay time of the ambient gas is short. To gain detailed insights into the mechanism of oil droplet explosion, the explosion process under initial pressures from 13 to 31 bar and temperatures from 700 to 1600 K was visualized using high-speed photography and microphotography on a rapid compression machine. The effects of temperature and shock waves were experimentally investigated, and droplet deformation after shock wave impact was calculated using a simple model. The results demonstrated that high temperature does not have a significant effect on droplet explosion under the conditions studied in this paper. The shock wave impact is the primary cause of the droplet’s explosion.

Flow control effect of pulsed arc discharge plasma actuation on impinging shock wave/boundary layer interaction

The current study investigates the control effect of the pulsed arc discharge plasma on the impinging shock wave and boundary layer interaction (SWBLI) generated by a 14° wedge in a Mach 2.5 flow. The response characteristics of SWBLI on pulsed arc discharge actuation were illustrated, and the controlling mechanism of shock-induced flow separation under different plasma power settings was revealed. The results, which were well validated by the relative published experiment, showed that when setting the exciting power density ph as 1.0 × 1011 W/m3, the oblique shock wave obtained an obvious fluctuation, and the foot of the reattachment shock wave was partially removed. In addition, as the controlling gas bubble passed through the interaction region, the reverse flow zone was enlarged, and the separation shock wave was shifted upward. When ph was set to 4.8 × 109 W/m3, the flow separation induced by SWBLI was effectively suppressed and the size of the reverse flow zone was significantly reduced. Moreover, as the energy input was increased, the arc-induced blast wave (BW) velocity was obviously enhanced. Additionally, it is further found that the arc plasma energy deposition density in the discharge region was the determining factor for SWBLI control, even for a relatively small exciting energy input. Better drag reduction of the flow field would be achieved with the pulsed arc discharge plasma of higher power density, and a drag reduction rate of nearly 10.05% was obtained at ph = 1 × 1011 W/m3 control condition.

Shock wave recovery experiments on poly-crystalline tri-glycine sulfate – X-ray and Raman analyses

Recent reports of shock wave experiments on non-linear optical (NLO) crystals have demonstrated outstanding results. Suitable candidates are currently being studied for industrial applications. For the present experiment, we have chosen tri-glycine sulfate (TGS) for the investigation of the structural properties after shock wave loaded conditions by employing X-ray diffraction and Raman spectroscopic measurements. The observed diffraction and spectroscopic patterns of the test polycrystalline sample reveal that the test sample does not undergo any crystallographic phase transition. But, there are several additional shoulder peaks observed and Raman measurements show that a few Raman bands appear while some disappear by the impact of shock waves due to the re-orientational effect of glycine molecules. The observed interesting results are discussed.

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

Theoretical analysis on the total pressure gain of rotating detonation systems

To achieve the positive total pressure gain of the aerospace propulsion system is one of the critical issues for the application of rotating detonation. This study conducts a theoretical analysis on the total pressure gain (PG) of a rotating detonation system (RDS) composed of the isolator, anti-backflow zone and detonation combustor, with the system inlet Mach number of Ma2. The impact of the reverse oblique shock wave (ROSW) on the system performance is emphasized. The definition of PG is based on the mass-weighted average pressure (MAP). An estimation method for PG is proposed, which is related to the inlet parameters and system anti-backflow capability. The approximate range of PG for the typical RDS and the parameter influence law are thus obtained. Results show that there is no guarantee that a positive PG can be achieved for the RDS. The theoretical upper limit PGmax is obtained when the ideal detonation cycle is realized, and its value mainly depends the reactant activity. The theoretical lower limit PGmin is mainly related to Ma2 and the area ratio of system inlet and outlet, and a specific range of Ma2 exists so that PGmin ≥ 0. When the ideal check valve (ICV) is employed, which can completely suppress the ROSW and cause no total pressure loss in the anti-backflow zone, the PGICV first increases and then decreases with the increase of Ma2, and reaches a maximum value when Ma2 approaches 1. For a general RDS, PG is always less than PGICV. The calculation example shows that for the stoichiometric C10H20/air mixture, the range of PG is ranged in (-1, 3). Eventually, two key approaches are needed to realize the positive PG of RDS, namely employing the ideal check valve, and making Ma2 approach 1 that is achieving the maximum inlet mass flux. The present study is guidable for the RDS design in practice.

Structural and morphological behaviours of l-Asparagine monohydrate at shocked conditions

Studies on the dynamic shock impact on solids also provide a magnificent scope of understating the stability of materials that are needed for high-pressure applications. Based on the impending investigations arising out of the observed experimental results of the shock-wave impact on solids, it is very much revealed that the impact of shock waves on molecular crystals is not yet well understood; especially amino acid crystals. Hence the present work deals with the assessment of crystallographic phase stability of l-Asparagine monohydrate (C4H8N2O3·H2O) amino acid powder samples against shocked-conditions and the results have been analyzed by X-ray powder diffractometry and scanning electron microscopy. The results of XRD and SEM reveal that the mother crystallographic phase of the title sample has significantly changed without inducing any crystallographic phase-transition and the observed structural modifications are discussed on the basis of previous publications reported on the static high-pressure study on the title sample.

Instability and Atomization of Liquid Cylinders after Shock Wave’s Impacting

This paper describes an experimental study on the instability and atomization of liquid cylinders after the impact of shock waves. Single row water column, in-line double rows water columns and alongside triple rows water columns were evaluated in a horizontal shock tube. The diameter of water column and the Mach number in the experiments were 2.0–4.14 mm and 1.10–1.25, respectively. The global instability along the axial direction of water cylinders was focused. Using a high-speed camera, the developments of spike height, bubble depth and turbulent mixing zone, width were measured. Some comparison was also made between the present experimental results and the existing theoretical model.

A study on the effect of driver section length on the flow field inside a two-dimensional closed-ended viscous shock tube: A numerical investigation

The interaction of a reflected shock wave with the boundary layer inside a closed-ended shock tube is studied by many researchers using different numerical schemes. However, the interaction of a reflected shock wave having a decaying pressure profile ahead of the reflected shock is lacking in the literature. It is essential to quantify the deviation in flow characteristics experienced in tests performed inside the shock tube compared to field tests while studying blast wave attenuation and mitigation. In the present study, the effect of transient upstream pressure on the shock wave reflecting from a solid wall and the associated flow separation inside the boundary layer is examined in detail through numerical simulations using the viscous shock tube problem for Re = 1000. Simulations were performed using an in-house 13th-order high-resolution hybrid solver with 50 million grid points. The transient pressure profile behind the incident shock wave is achieved by varying the non-dimensional driver section length from 0.5 to 0.02 while keeping the overall shock tube length as 1. The flow field is scrutinized through numerical schlieren and vorticity plots. It is observed that the decaying pressure profiles behind the incident shock wave have an immense impact on the dynamics of shockwave-boundary layer interaction and the vortices emanating from the shear layer due to Kelvin–Helmholtz Instability. The secondary vortices inside the boundary layer, vortices at the shear layer, and compression waves in the separated boundary layer region reduce with a decrease in driver section length. The triple point height increases as driver section length decreases due to the weakening of upstream velocity. The Kelvin–Helmholtz vortices originating from the triple point moves back into the separated boundary layer rather than interacting with the end wall. It suggests that the decaying pressure behind the incident shock wave minimizes the secondary effects on the solid wall during shock wave impingement.

Effect of interaction strength on recovery downstream of incident shock interactions

Direct numerical simulations of a supersonic turbulent boundary layer on a flat plate interacting with an impinging shock wave are carried out with two different incident shock angles at Mach 2.25. The effect of the interaction strength on the recovery process in the downstream region is systematically studied, including the turbulence evolution, the statistical and structural properties of wall pressure fluctuations, and the generation of mean skin friction and wall heat flux. The variations of the Reynolds stress components, the anisotropy tensor, and the turbulent kinetic energy budget in the two flow cases highlight a slow reversal tendency and an increasingly pronounced importance of the outer-layer large-scale structures in the relaxation region of the strong interaction. We find that the effect of increasing the interaction strength on the fluctuating wall pressure is reflected by a decrease in the characteristic frequencies, an increase in the spatial extent, and a decrease in the convection velocity. We decompose the mean skin friction and wall heat flux into different physically informed contributions and reveal that the mean wall heat flux generation is the same regardless of the interaction strength; in contrast, the generation mechanism of mean skin friction is found to be fundamentally changed. A novel scale-decomposition method is used to quantify the effect of the increased interaction strength on the leading components, and it is demonstrated that the energetic outer-layer large-scale structures are the dominant contributor in the recovery process as the interaction strength is increased.

Effect of shock wave impact on natural chitosan biopolymer

In the present study, the influence of shockwave impact on chitosan (CS) material samples is investigated. The shock tube is used to create the shock wave and the experiments are conducted for a shock Mach number of 1.6. CS material sample is exposed to the shock wave by fixing at the driven tube end flange and impacted to 30, 60 and 90 shock impulses. CS material after the impact was characterized for its structural changes by the Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and viscometer results. The FT-IR results of the treated sample indicate that the bond length is reduced as the functionality of amide increases by lowering the mass of the samples. Significant changes are observed for the CS samples exposed to 90 shock pulses. The degree of deacetylation is increased from 75% to 89%. XRD results indicate that the crystallite size is enhanced by 109% in the treated samples and significant morphological changes are noticed in the SEM images. The viscosity is decreased to 88% and the reduction in molecular weight by 92% indicates the shock-treated CS samples contain high water solubility. Results emphasized that the shock tube technique yields quick findings with favorable changes in the CS depolymerization reaction and demonstrated that it is an efficient, cost-effective and less time-consuming approach.

The impact of low-intensity extracorporeal shock waves on testicular spermatogenesis demonstrated in a rat model.

In rodent models, low-intensity extracorporeal shock wave therapy has been shown to negatively impact semen concentration after treatment on the penis, implying that the reproductive system in close proximity may be indirectly affected by this modality. We hypothesized that shock waves are detrimental to spermatogenesis, and the aim of this study was to evaluate the effect of shock waves on spermatogenesis after direct shockwave treatment on testes using different energy settings. Twenty-five male Sprague Dawley rats, 8 weeks old, were divided into five groups, including one control group and four treatment groups each treated using shock waves of different intensities. All rats in the treatment groups received 2000 shocks on the left testis twice a week for 4 weeks, with shock wave intensity and frequency varied by treatment group: 0.1 mJ/mm 2 at 4 Hz for Group A, 0.15 mJ/mm 2 at 4 Hz for Group B, 0.35 mJ/mm 2 at 4 Hz for Group C, and 0.55mJ/mm 2 at 3 Hz for Group D. At the end of the experiment, sperm collected from the epididymis was evaluated for concentration and motility. Testicular spermatogenesis, the apoptotic index of germ cells, and the expression of a meiotic-specific gene were also analyzed. The treatment group receiving shock wave intensity at 0.55 mJ/mm 2 showed a significant decrease in sperm concentration, motility, and Johnsen score as compared to other groups. The apoptotic index of spermatogenic cells increased as the intensity of the shock wave treatment escalated, and reach a statistically significant difference at 4 weeks posttreatment. Treating testes with intensity levels of 0.55 mJ/mm 2 at 3 Hz interfere with the quality or quantity of spermatogenesis and also increases in spermatogenic cell apoptosis, whereas the expression of the SYCP3 gene significantly decreased after treatment with intensity levels of 0.10 mJ/mm 2 , 0.15 mJ/mm 2 , and 0.35 mJ/mm 2 at 4 Hz. Treating testes with intensity levels of 0.55 mJ/mm 2 at 3 Hz interfere with the quality or quantity of spermatogenesis and also increases spermatogenic cell apoptosis, whereas the expression of the SYCP3 gene significantly decreased after treatment with intensity levels of 0.10 mJ/mm 2 , 0.15 mJ/mm 2 , and 0.35 mJ/mm 2 at 4 Hz.