Explosion Condition Research Articles

Including Neutrino-driven Convection in the Force Explosion Condition to Predict Explodability of Multidimensional Core-collapse Supernovae (FEC+)

Most massive stars end their lives with core collapse. However, it is not clear which explode as a core-collapse supernova (CCSN), leaving behind a neutron star, and which collapse to a black hole, aborting the explosion. One path to predict explodability without expensive multidimensional simulations is to develop analytic explosion conditions. These analytic conditions also provide a deeper understanding of the explosion mechanism and they provide some insight into why some simulations explode and some do not. The analytic force explosion condition (FEC) reproduces the explosion conditions of spherically symmetric CCSN simulations. In this follow-up manuscript, we include the dominant multidimensional effect that aids explosion—neutrino-driven convection—in the FEC. This generalized critical condition (FEC+) is suitable for multidimensional simulations and has potential to accurately predict explosion conditions of two- and three-dimensional CCSN simulations. We show that adding neutrino-driven convection reduces the critical condition by ∼30%, which is consistent with previous multidimensional simulations.

Dynamic Response and Damage Characteristics of Large Reinforced Concrete Slabs under Explosion

To investigate the damage characteristics of reinforced concrete (RC) buildings during explosive incidents, a large RC slab (4 m × 5 m × 0.15 m) was meticulously designed, fabricated, and subjected to explosion experiments, which were complemented by comprehensive numerical simulations. The dynamic response parameters of the RC slabs under 0.5–1 kg TNT explosions were tested using polyvinylidene fluoride (PVDF) pressure sensors, displacement sensors, and acceleration sensors. The damage morphologies under 5–40 kg TNT explosions were investigated using ANSYS/LS–DYNA 17.0 software. The results show that, with an increase in TNT charge, the RC slab gradually showed minor damage (5 kg), moderate damage (10–20 kg), heavy damage (25 kg), and complete destruction (30–40 kg). For the 20 kg TNT explosion condition, a 1020 mm × 760 mm explosion crater appeared on the top surface, which was in agreement with the 934 mm × 906 mm explosion crater obtained from the simulation. Based on the results, suitable P–I (pressure–impulse) curves for the 4 m × 5 m × 0.15 m RC slab were established. The results can provide a reference for damage assessments of large-sized buildings during explosion accidents.

The effects of superstructure form on damage characteristics of ship subjected to underwater explosion

To investigate the influence of superstructure on the damage characteristics of ships subjected to a near-field underwater explosion, two hull girder models with different superstructures were designed basing on the principle of similarity. The experiment and numerical simulation were conducted to attain the dynamic response of the models. In addition, this paper discussed the impact of the structure and layout modifications of the superstructure on the hull girder’s damage and simply analyzed the overall and local coupling damage characteristics of the hull. The results show that the presented numerical simulation could accurately predict the hull girder’s overall damage mode and deformation. Under the same explosion condition, the presence of the superstructure increases the hull girder’s resistance to the overall bending deformation and minimizes the damage of grillage at the hull bottom. When the abrupt change of cross-section location is within the range of 1/10 girder length from the girder’s midspan (to the bow or stern), the failure mode of the hull girder is sagging damage. The length of the superstructure of the hull girder should be limited to 0.4–0.8 times the hull’s length; hence, the superstructure and the main hull can resist bending deformation more effectively.

The force explosion condition is consistent with spherically symmetric CCSN explosions

ABSTRACT One of the major challenges in core-collapse supernova (CCSN) theory is to predict which stars explode and which collapse to black holes. The analytic force explosion condition (FEC) shows promise in predicting which stars explode in that the FEC is consistent with CCSN simulations that use the light-bulb approximation for neutrino heating and cooling. In this follow-up manuscript, we take the next step and show that the FEC is consistent with the explosion condition when using actual neutrino transport in gr1d simulations. Since most 1D simulations do not explode, to facilitate this test, we enhance the heating efficiency within the gain region. To compare the analytic FEC and radiation-hydrodynamic simulations, this manuscript also presents a practical translation of the physical parameters. For example: we replace the neutrino power deposited in the gain region, Lντg, with the net neutrino heating in the gain region; rather than assuming that $\dot{M}$ is the same everywhere, we calculate $\dot{M}$ within the gain region; and we use the neutrino opacity at the gain radius. With small, yet practical modifications, we show that the FEC predicts the explosion conditions in spherically symmetric CCSN simulations that use neutrino transport.

Determination of thickness parameters of detonation shell and safety performance analysis

AbstractOn the premise of security, it is necessary to ensure good operational performance and technical indicators for nonlethal weapons such as flash detonation bombs. To make the weight of a flash detonation grenade more convenient for hand throwing and material costs save, the outer dimensions of the grenade body are fixed, and the optimal parameters of outer shell thickness of the vertigo grenade are explored. Based on the maximum deformation energy theorem, the strength of the shell with the obtained maximum thickness of 8 mm is checked, and then the optimal shell thickness under the ideal air explosion condition is obtained by reducing the thickness; Then check the thread strength to obtain the inner casing fracture, shock wave, and sound pressure level. The fragmentation performance test, detonation test, and sound pressure level test were carried out for the projectiles involving the shell thickness of 4 and 5 mm, and the simulation results were verified from three aspects of sound intensity, shell strength, and fragments. The results show that the maximum equivalent stress is 232.6 MPa and the maximum deformation is 1.07 × 10−4 mm when the outer shell thickness of the vertigo grenade is 5 mm, which is less than the material failure strength standard and no plastic deformation could occur. The structural connection strength of the missile body meets the standard. Most of the fragments are trapped in the cavity. The average sound pressure level at 1.5 m can reach 159.7 dB. The relative error between the sound pressure level at 3 m and the live ammunition test results is 4.8%, which meets the expected operational technical indicators and has good safety performance. The results of the numerical simulation can provide a reference for the design optimization and performance evaluation of similar vertigo grenades.

The essential character of the neutrino mechanism of core-collapse supernova explosions

Abstract Calibrating with detailed 2D core-collapse supernova (CCSN) simulations, we derive a simple CCSN explosion condition based solely upon the terminal density profiles of state-of-the-art stellar evolution calculations of the progenitor massive stars. This condition captures the vast majority of the behaviour of the one hundred 2D state-of-the-art models we performed to gauge its usefulness. The goal is to predict, without resort to detailed simulation, the explodability of a given massive star. We find that the simple maximum fractional ram pressure jump discriminant we define works well ∼90 per cent of the time and we speculate on the origin of the few false positives and false negatives we witness. The maximum ram pressure jump generally occurs at the time of accretion of the silicon/oxygen interface, but not always. Our results depend upon the fidelity with which the current implementation of our code F ornax adheres to Nature and issues concerning the neutrino–matter interaction, the nuclear equation of state, the possible effects of neutrino oscillations, grid resolution, the possible role of rotation and magnetic fields, and the accuracy of the numerical algorithms employed remain to be resolved. Nevertheless, the explodability condition we obtain is simple to implement, shows promise that it might be further generalized while still employing data from only the unstable Chandrasekhar progenitors, and is a more credible and robust simple explosion predictor than can currently be found in the literature.

Alkali Impregnation and Steam Explosion of Cogon Grass for Improved Enzymatic Saccharification

Process parameters for the alkali-impregnation of cogon and its combination with steam explosion were evaluated and optimized using Response Surface Modeling (RSM). Dried cogon (10% w/v) was impregnated in diluted base (1, 2, 3% (w/w) NaOH) at different ranges of temperature (50, 85,120 °C) and time (15, 32.5, 50 min), and then subjected to enzymatic saccharification using 60 FPU/g Accelerase 1500TM. The concentration of reducing sugar released was measured using Nelson-Somogyi Colorimetric Method. The RSM showed that the optimum condition, predicting 10% Reducing Sugar Yield (RSY), was treatment of 10 % (w/v) cogon with 1.5% NaOH (w/v) at 73 °C for 15 min. Upon validation, done in triplicates, 13+1.0% RSY was obtained. The optimally-impregnated cogon was subjected to a steam explosion treatment to improve its saccharifiability. The factors varied were temperature (170 to 225 °C) and exposure time (250 to 800 s). Upon saccharification of the steam-exploded samples, the RSM indicated that the best steam explosion condition, predicting 14% RSY, was 225 °C and 800 s. Upon validation, 15+0.5% RSY was obtained. Steam explosion improved the saccharifiability of NaOH-impregnated cogon by 15%.

A force explosion condition for spherically symmetric core-collapse supernovae

ABSTRACT Understanding which stars explode leaving behind neutron stars and which stars collapse forming black holes remains a fundamental astrophysical problem. We derive an analytic explosion condition for spherically symmetric core-collapse supernovae. The derivation starts with the exact governing equations, considers the balance of integral forces, includes the important dimensionless parameters, and includes an explicit set of self-consistent approximations. The force explosion condition is $\tilde{L}_\nu \tau _g - 0.06 \tilde{\kappa } \gt 0.38$, and only depends upon two dimensionless parameters. The first compares the neutrino power deposited in the gain region with the accretion power, $\tilde{L}_\nu \tau _g = L_{\nu } \tau _g R_{\rm NS}/ (G \dot{M} M_{\rm NS})$. The second, $\tilde{\kappa } = \kappa \dot{M} / \sqrt{G M_{\rm NS} R_{\rm NS}}$, parametrizes the neutrino optical depth in the accreted matter near the neutron star surface. Over the years, many have proposed approximate explosion conditions: the critical neutrino-luminosity, ante-sonic, and time-scale conditions. We are able to derive these other conditions from the force explosion condition, which unifies them all. Using numerical, steady-state and fully hydrodynamic solutions, we test the explosion condition. The success of these tests is promising in two ways. One, the force explosion condition helps to illuminate the underlying physics of explosions. Two, this condition may be a useful explosion diagnostic for more realistic, three-dimensional radiation hydrodynamic core-collapse simulations.

Ocular biomechanics during improvised explosive device blast: A computational study using eye-specific models

BackgroundEye injuries comprise 10–13% of civilian improvised explosive device (IED) injuries. The bomb blast wave induces a normal and shear forces on the tissues, causing a large acute IOP elevation. This study calculated the biomechanical stresses and strains in the eye due to IED explosion via eye-specific fluid-structure interaction (FSI) models. MethodsBlast occurred at 2, 3, and 4 m from the front and side of the victim and the weights of the IED were 1 and 2 kg. The ground was covered with the deformable soil to mimic the realistic IED explosion condition and reflect the blast wave. ResultsThe IOP elevation of ∼6,000–48,000 mmHg was observed in the eyes while the highest IOP was occurred with the IED weight and distance of 2 kg and 2 m (front) and the lowest was occurred with the IED weight and distance of 1 kg and 4 m (side). Our findings suggest the importance of the victim location and orientation concerning the blast wave when it comes to ocular injury assessment. IOP elevation of ∼2900 and ∼2700 mmHg were observed in ∼1.6 ms after the blast for the IEDS weight of 2 kg and a victim distance of 2 m in front and side blasts, respectively, in consistence with the literature. Nonetheless, IOPs were considerably higher after ∼1.6 ms due to the merging of the bomb blast wave and its reflection off the ground. ConclusionsThe stresses and strains were highest for the frontal blast. Both side and frontal blasts caused higher stresses and strains at the rectus muscle insertions where the sclera is thinnest and prone to rupture. Blast angle has no considerable role in the resultant IOP. Front blast with a heavier IED resulted a higher stresses and deformations in the eye connective tissues compared to the side blast.

Competition of Electron Capture and Beta Decay Rates in Explosive Astrophysical Scenario of Type II Supernova

Stellar weak interaction processes play a significant role during the supernova explosion condition after collapse leading to the formation of neutron star. In dynamic events like core-collapse supernovae the high entropy wind scenario arises from considerations of the newly born proto-neutron star. Here, the late neutrinos interact with matter of the outermost neutron star layers leading to moderately neutron rich ejecta. We study the electron capture and beta decay rates of Co and Cd isotopes at various temperature and density conditions in an astrophysical environment and found that the beta decay rates are much higher than the corresponding electron capture rates at all the conditions.

Research on Jet Incoherence of Depleted Uranium Liner

Jet formation is the decisive factor of penetrating power of shaped charge, coherence and stability contribute to penetration. In the same condition, multiple penetrating tests of the shaped charge with depleted uranium(DU) liner did not get the expected results. In order to study the jet forming characteristics of DU liner under static explosion condition, an X-ray photography experiment was designed, which turned out to show the jet being badly incoherent. To research the incoherence of DU shaped charge jet from principles of jet incoherence, supersonic collision worked out to be the reasons for incoherence of the shaped charge jet. This paper provides a method for structural optimization of DU shaped charge and DU liner processing, which has guiding significance for application of DU liner in high explosive antitank projectile.

Effect of Steam Explosion Condition on the Improvement of Physicochemical Properties of Pine Chips for Feed Additives

Dietary fiber is considered a feed ingredient with high nutritional value in the broiler feed industry. Pine chips contain a large amount of dietary fiber and require some modification for use as broiler feed. In this study, pine chips were subjected to steam explosion under different severity factor (Ro) conditions to improve the chemical and physical properties of dietary fiber. The highest water-holding capacity, oil-holding capacity, and swelling capacity were found for Ro 4.0, followed by Ro 4.5 and 3.5. The optimal condition for the steam explosion was determined to be Ro 4.0 (reaction temperature of 210°C, and reaction time of 6.0 min). Under these conditions, the water-holding capacity, oil-holding capacity, and swelling capacity of steam-exploded pine chips were 8.3 g/g, 6.5 g/g, and 5.0 mL/g, respectively. This study may contribute to the application of lignocellulose and related products in the broiler feed industry.

Determination and evaluation of Holmquist-Johnson-Cook constitutive model parameters for ultra-high-performance concrete with steel fibers

Ultra-high performance concrete (UHPC) features with exceedingly high strength and fracture energy, and thus is regarded as a promising structural material to resist impact and blast loadings. Particularly, adding steel fibers can significantly enhance the impact resistance of UHPC. To facilitate the simulation of the behavior of UHPC structures with various steel fiber ratios against extreme loadings, selecting an appropriate constitutive model and determining its parameters should be highly emphasized. The Holmquist-Johnson-Cook (HJC) model is widely used in the simulation of the conventional concrete subjected to impact and explosion, whereas there are rare studies on calibrating the parameters of the HJC model for UHPC. In this study, a set of HJC model parameters for UHPC with considering the volume ratio of steel fiber ranging from 0% to 3% were firstly determined based on existing test data, originating from the Split-Hopkinson pressure bar (SHPB) test, triaxial test, uniaxial loading test, and Hugoniot test. To verify the correctness of the calibrated parameters of HJC model, UHPC slabs under the contact explosion condition were then tested, and a finite element model (FEM) with the calibrated parameters implemented was thereby established to reproduce this experiment numerically. Finally, the existing bullet penetration experiment was also verified with the numerical procedure. The results show that finite element simulations by employing the HJC model with calibrated parameters agree well with the experiments. The successful applications and evaluation of the HJC model with calibrated parameters in this work can provide guidance in simulating the behavior of UHPC with certain prescribed steel fiber ratio subjected to the impact and blast loading.

Research on drop tower technology for simulating explosive impact load

When military vehicles are subjected to a mine blast, the vehicles will be damaged and the occupants will be injured. The main objective of this paper is to study the feasibility and accuracy of the drop tower to simulate the response of the vehicle body under the actual explosion condition. The equivalent damage method of impact waveform simulation was studied, and the feasibility of the equivalent damage principle of impact waveform based on change in velocity was verified. By analyzing a large number of data of simplified seat impact simulation, the mechanical model of the drop tower was analyzed. Through the correlation study of the parameters of the drop impact load, the relation formula of the drop height required by the target load was constructed, and the customization of the impact load was realized. The response simulation of the protective seat in the explosion was completed in the drop tower, which verifies the accuracy of the drop tower in simulating the explosion impact load. In addition, the results provide a good basis for the follow-up research.

Characteristics of closed and vented explosions of gasoline-air mixture in a square tube

In order to investigate the closed explosion and venting characteristics of gasoline-air mixture, two kinds of explosion modes were studied by using a visualized square tube, and numerical simulation was carried out based on the wall-adapting local eddy-viscosity (WALE) model and Zimont premixed flame model. The results show the followings. (1) The number of the peaks on the overpressure time series curve for the vented explosion is greater than that for the closed explosion, and there is a violent oscillation similar to a simple harmonic vibration on the overpressure time series curve of the vented explosion, while the characteristic parameters of explosion overpressure in the closed explosion are significantly higher than those in the vented explosion. (2) The maximum flame propagation speed in the closed explosion is significantly lower than that in the vented explosion, but the former reaches the maximum at the beginning of flame propagation, while the latter reaches the maximum at the end of flame propagation. (3) Tulip-shaped flame appears in the closed explosion condition, while mushroom-shaped flame appears in the venting condition. The formation of the tulip-shaped flame is related to the coupling effects of flame front, flow field and dynamic pressure of flow field in the pipe, while the mushroom-shaped flame is caused by the combined action of turbulence and baroclinic effect in the external flow field.

Dynamic and whipping response of the surface ship subjected to underwater explosion: experiment and simulation

ABSTRACT The dynamic and the whipping phenomena through an underwater explosion (UNDEX) experiments and simulations were verified. Furthermore, the comparison of the simulation and experimental results were conducted. The experiment was conducted at a reservoir and the MegaMEX was used as an explosive. The simulation was performed by combining the DAA-based USA code with the LS-Dyna which is a finite element analysis code, and for the gas bubble, the second-generation Geers–Hunter model was used. For the experiment, the natural frequency analysis of the structure was carried out to establish the explosion condition and four underwater explosion tests were carried out. Acceleration, velocity, strain and underwater pressures were measured by underwater explosion experiments, and acceleration, velocity and strain were compared. In this research, the whipping phenomenon by underwater explosion was confirmed through experiments and simulation. The results of this study are expected to contribute to the improvement of UNDEX simulation technique.

Study on theoretical calculation of quasi-static pressure for explosion in confined space

Objectives The process of explosion in confined space involves not only the propagation and reflection of shock waves, but also complex afterburning effect. The afterburning effect not only enhances the shock wave intensity, but also has a great influence on the final quasi-static pressure. In order to give a prediction of the quasi-static overpressure for explosion inside confined space, Methods a theoretical model for calculation of the peak valve of the quasi-static overpressure for confined explosions considering afterburning effects was proposed based on the analysis of chemical reactions and the law of conservation of energy. The results calculated by the model were then analyzed and compared with the literatures' as well as the empirical formulas' to verify the reliability and correctness of the proposed model. Results The results show that, the peak value of the quasi-static overpressure calculated by theoretical model is in good agreement with the results of the experimental measurement and from the empirical formulas in the literature; the Anderson's empirical formula is inapplicable to the confined explosion condition in case of a small mass volume ratio of less than 0.5 kg/m3, and the formula given in the reference [ 8 ] may not be extrapolated to the confined explosion conditions with a large ratio of greater than 8.87 kg/m3. Conclusions The study in this paper can provide a better understanding of the physical mechanism of the contribution of afterburning effect to quasi-static pressure, and provide some reference and guidance for the design of explosion-resistant structures and damage assessment.

Asymptotic error distribution for the Euler scheme with locally Lipschitz coefficients

In traditional works on numerical schemes for solving stochastic differential equations (SDEs), the globally Lipschitz assumption is often assumed to ensure different types of convergence. In practice, this is often too strong a condition. Brownian motion driven SDEs used in applications sometimes have coefficients which are only Lipschitz on compact sets, but the paths of the SDE solutions can be arbitrarily large. In this paper, we prove convergence in probability and a weak convergence result under a less restrictive assumption, that is, locally Lipschitz and with no finite time explosion. We prove if a numerical scheme converges in probability uniformly on any compact time set (UCP) with a certain rate under a global Lipschitz condition, then the UCP with the same rate holds when a globally Lipschitz condition is replaced with a locally Lipschitz plus no finite explosion condition. For the Euler scheme, weak convergence of the error process is also established. The main contribution of this paper is the proof of n weak convergence of the normalized error process and the limit process is also provided. We further study the boundedness of the second moments of the weak limit process and its running supremum under both global Lipschitz and locally Lipschitz conditions.

Optimization of Acid and Steam Explosion Pretreatment of Cogon Grass for Improved Cellulose Enzymatic Saccharification

Acid-impregnation and its combination with steam explosion were evaluated and optimized using Response Surface Methodology. At 10% solid-liquid ratio, cogon was impregnated with diluted H2SO4 solution (0 to 3%, w/w) at different ranges of temperature (40 to 120 °C) and varied time (0 to 130 min). Impregnated samples were then subjected to enzymatic saccharification using 60 FPU/g Accelerase 1500™. After enzymatic saccharification, the concentration of reducing sugar released was measured using Dinitrosalicylic (DNS) Colorimetric Method. Based on the results, Response Surface Model (RSM) showed that the optimum condition, predicting 7.18% Reducing Sugar Yield (RSY), was impregnation of cogon using 1.9% H2SO4 at 91.8 °C for 56 min. Experimental verification of optimum condition, done in triplicates, showed 6.35 + 0.05% RSY. Acid-impregnated cogon was subjected to steam explosion to improve saccharifiability. Factors varied were temperature (137 to 222 °C) and exposure time (17 to 582 s). Steam-exploded samples were saccharified and RSY was determined. RSM indicated that the best steam explosion condition, predicting 7.91% RSY, was 179 °C and 500 s. Experimental verification of optimum condition showed 8.78 + 0.02% RSY. Using RSY as basis, steam explosion improved saccharifiability of H2SO4-impregnated cogon by 38%, thus, increasing production of reducing sugars for potential bioethanol production.

Effect of pre-deformation mode on the microstructures and mechanical properties of Hadfield steel

The microstructures and tensile properties of a conventional Hadfield steel subjected to explosion and cold rolling deformation modes were investigated in the current study. The deformation mode significantly changed the microstructure and tensile properties of the Hadfield steel. The grains in cold rolling condition were largely elongated along the rolling direction; however most grains in the exploded sample retained their equiaxed morphologies. The strain concentration was localized at the grain boundaries, and the change in the population of ∑3 annealing twin and ∑9 boundaries was smaller in the exploded sample than in the rolled condition. Moreover, the deformation twins were formed uniformly along grain boundaries in the Hadfield steel under the explosion condition. However, they primarily appeared as twin bundles in the cold rolled state. The change in the microstructure characteristics resulted in higher yield strength but lower tensile strength and elongation in the exploded sample compared with the cold rolled condition.