Explosion Models Research Articles

High γ-ray escape time in 2003fg-like supernovae: A challenge to proposed models

Abstract A rare subclass of Type Ia supernovae (SNe Ia), named after the prototype SN 2003fg, includes some of the brightest SNe Ia, often called ”super Chandrasekhar-mass” SNe Ia. We calculate the γ-ray deposition histories and the 56Ni mass synthesized in the explosion, MNi56, for eight 2003fg-like SNe. Our findings reveal that the γ-ray escape time, t0, for these objects is t0 ≈ 45–60 days, significantly higher than that of normal SNe Ia. 2003fg-like SNe are distinct from normal SNe Ia in the t0–MNi56 plane, with a noticeable gap between the two populations. The observed position of 2003fg-like SNe in this plane poses a significant challenge for theoretical explosion models. We demonstrate that the merger of two white dwarfs (WDs) and a single star exceeding the Chandrasekhar limit fail to reproduce the observed t0–MNi56 distribution. However, preliminary calculations of head-on collisions of massive WDs show agreement with the observed t0–MNi56 distribution.

Spectroscopic analysis of the strongly lensed SN Encore: Constraints on cosmic evolution of Type Ia supernovae

Abstract Strong gravitational lensing magnifies the light from a background source, allowing us to study these sources in detail. Here, we study the spectra of a z = 1.95 lensed Type Ia supernova SN Encore for its brightest Image A, taken 39 days apart. We infer the spectral age with template matching using the supernova identification (SNID) software and find the spectra to be at 29.0 ±5.0 and 37.4 ±2.8 rest-frame days post maximum respectively, consistent with separation in the observer frame after accounting for time-dilation. Since SNe Ia measure dark energy properties by providing relative distances between low- and high-z SNe, it is important to test for evolution of spectroscopic properties. Comparing the spectra to composite low-z SN Ia spectra, we find strong evidence for similarity between the local sample and SN Encore. The line velocities of common SN Ia spectral lines, Si II 6355 and Ca II NIR triplet are consistent with the distribution for the low-z sample as well as other lensed SNe Ia, e.g. iPTF16geu (z = 0.409)and SN H0pe (z = 1.78). The consistency between the low-z sample and lensed SNe at high-z suggests no obvious cosmic evolution demonstrating their using as high-z distance indicators, though this needs to be confirmed/refuted via a larger sample. We also find that the spectra of SN Encore match the predictions for explosion models very well. With future large samples of lensed SNe Ia e.g. with the Vera C. Rubin Observatory, spectra at such late phases will be important to distinguish between different explosion scenarios.

Numerical investigation of dual‐source gas explosion dynamics in h‐type tunnels under varied enclosed situations

AbstractTo further investigate the propagation characteristics of shock waves and flame waves in H‐type tunnel gas explosions, numerical simulation studies were conducted on a dual‐source gas explosion model using Fluent software. Three distinct operational conditions were designed and modeled, leading to the following outcomes. The shock wave flow field parameters from dual sources (with equal source energy) are symmetrically distributed in the H‐type tunnel, with high pressure and low flow velocity in the connecting roadway between the two shock waves. Under different conditions, the pressure is generally higher in closed tunnels (fully closed greater than semi‐closed) and lower in open tunnels. The largest overpressure in non‐explosion areas occurs at the closed ends and in the connecting roadway, while the areas bearing the greatest impulse are the shock wave reflection zones and pressure coupling regions. In closed conditions, the flame wave first moves forward and then propagates backward after the explosion, influenced by reflected waves and pressure differences between the ends and the tunnel. In open conditions, the pressure in the flame zone is lower than at both ends, inhibiting the forward propagation of the flame wave.

High γ-ray escape time in 2003fg-like supernovae: a challenge to proposed models

ABSTRACT A rare subclass of Type Ia supernovae (SNe Ia), named after the prototype SN 2003fg, includes some of the brightest SNe Ia, often called ‘super Chandrasekhar-mass’ SNe Ia. We calculate the $\gamma$-ray deposition histories and the $^{56}$Ni mass synthesized in the explosion, $M_\mathrm{Ni56}$, for eight 2003fg-like SNe. Our findings reveal that the $\gamma$-ray escape time, $t_0$, for these objects is $t_0\approx 45\!-\!60 \,$ d, significantly higher than that of normal SNe Ia. 2003fg-like SNe are distinct from normal SNe Ia in the $t_0$–$M_\mathrm{Ni56}$ plane, with a noticeable gap between the two populations. The observed position of 2003fg-like SNe in this plane poses a significant challenge for theoretical explosion models. We demonstrate that the merger of two white dwarfs (WDs) and a single star exceeding the Chandrasekhar limit fail to reproduce the observed $t_0$–$M_\mathrm{Ni56}$ distribution. However, preliminary calculations of head-on collisions of massive WDs show agreement with the observed $t_0$–$M_\mathrm{Ni56}$ distribution.

Interaction between underwater explosion bubbles and soil–water interface: A numerical and experimental study

To explore the interaction between underwater explosion bubbles and soil–water interface, a near soil–water interface underwater explosion model based on the arbitrary Lagrangian–Eulerian method was established in this work. The peak pressure of the shock wave, maximum bubble radius, and bubble evolution in free-field and bottom-charge underwater explosions determined from the proposed simulation were highly consistent with the experimental results, thereby validating the proposed numerical model. The effects of the explosion distance and amount of explosive charge on the bubble–soil surface interaction were evaluated. The results showed that the reflection coefficient of the soil–water interface was in the range of 1.204–1.250, suggesting that it was hardly affected by the explosion distance and amount of explosive charge. The attenuation coefficient of the saturated soil was found to be 1.058. With the decrease in the explosion distance, the period and maximum radius of the bubbles slightly increased, and soil deformation increased as the lower surface of the bubbles was closer to the soil surface. For explosion distances of 0.3 and 0.4 m, only an overall movement of the soil surface was observed. When the explosion distance was 0.2 m or lower, a powerful downward jet was generated upon the pulsation of the first bubble, resulting in craters and slender depressions in the soil. With the increase in the amount of explosive charge, the period and maximum radius of the bubbles increased, and soil deformation also increased. These findings are expected to help advance our understanding of underwater explosion dynamics.

Damage calculation method for prestressed thin-walled aqueducts subjected to water pressure blasting

In recent years, the blast resistance of hydraulic structures under explosion loads has attracted more and more attention. The damage calculation method of prestressed aqueducts subjected to blasting load is still a complicated problem. For this purpose, the theory of computation of the water pressure blasting is introduced and the formula for calculating the charge weight of the water pressure blasting is presented. The accuracy of the Coupled Eulerian-Lagrangian (CEL) algorithm of the underwater explosion model is verified by the previous experiment. Then, a fully coupled three-dimensional numerical model of a prestressed aqueduct is established to acquire the dynamic performances and failure mechanisms of the prestressed aqueduct subjected to water pressure blasting. The influence of the prestress and pull rod on nonlinear dynamic performances and failure modes of a prestressed aqueduct subjected to water pressure blasting are discussed. Finally, based on the wave and material mechanics, a method of calculation for the prestressed aqueduct subjected to water pressure blasting is presented. The accuracy of the suggested method is validated by the damage mode of the prestressed aqueduct subjected to water pressure blasting under various TNT weights. The analysis results show that the proposed method can satisfy the relationship between the damage characteristics of the prestressed aqueduct to water pressure blasting and various TNT weights. 1.5 kg TNT is insufficient to completely shatter the prestressed aqueduct, while 3.5 kg TNT can cause a perfect crushing effect. 7.5 kg TNT will result in excessive fragmentation of the prestressed aqueduct and inefficient utilization of the explosive energy. The proposed damage calculation method can provide significant support for explosion analysis of the prestressed thin-walled aqueduct structure.

Integration of the exploding foil initiator with capacitor discharge unit and its performance characterization

This study presents a novel integrated exploding foil initiator system (EFIs), consisting of a planar switch, an EFI chip, and a capacitor. Additionally, we propose an evaluation method for integrated EFIs that combines numerical simulations with experimental testing, enabling a thorough assessment of their performance. Under test conditions of 900 V/0.22 μF, the EFI demonstrated an inductance of 10.2 nH and a resistance of 107.5 mΩ, measured via the sampling resistance method. The operational behavior of the EFIs was analyzed through a two-dimensional metal electrical explosion model and a one-dimensional flyer propulsion model, with the results compared to experimental data. Results indicated that under 900–1200 V/0.22 μF, the deviations between measured and calculated values for electrical explosion performance and flyer velocity were both within 5 %, validating the accuracy of the evaluation approach. Firing tests further confirmed that the EFIs successfully detonated HNS-IV at 1000 V/0.22 μF.

Hydrodynamics and Nucleosynthesis of Jet-driven Supernovae. II. Comparisons with Abundances of Extremely Metal-poor Galaxies and Constraints on Supernova Progenitors

The spectra of several galaxies, including extremely metal-poor galaxies from EMPRESS, have shown that the abundances of some Si-group elements differ from “spherical” explosion models of massive stars. This leads to the speculation that these galaxies have experienced supernova explosions with high asphericity, where mixing and fallback of the inner ejecta with the outer material lead to the distinctive chemical compositions. In this paper, we consider the jet-driven supernova models by direct 2D hydrodynamics simulations using progenitors of about 20–25 M ⊙ at zero metallicity. We investigate how the abundance patterns depend on the progenitor mass, mass cut, and asphericity of the explosion. We compare the observable with available supernova and galaxy catalogs based on 56Ni, ejecta mass, and individual element ratios. The proximity of our results with the observational data signifies the importance of aspherical supernova explosions in chemical evolution of these galaxies. Our models will provide the theoretical counterpart for understanding the chemical abundances of high-z galaxies measured by the James Webb Space Telescope.

SN 2021wvw: A Core-collapse Supernova at the Subluminous, Slower, and Shorter End of Type IIPs

We present detailed multiband photometric and spectroscopic observations and analysis of a rare core-collapse supernova, SN 2021wvw, that includes photometric evolution up to 250 days and spectroscopic coverage up to 100 days postexplosion. A unique event that does not fit well within the general trends observed for Type IIP supernovae, SN 2021wvw shows an intermediate luminosity with a short plateau phase of just about 75 days, followed by a very sharp (∼10 days) transition to the tail phase. Even in the velocity space, it lies at a lower velocity compared to a larger Type II sample. The observed peak absolute magnitude is −16.1 mag in r-band, and the nickel mass is well constrained to 0.020 ± 0.006 M ⊙. Detailed hydrodynamical modeling using MESA+STELLA suggests a radially compact, low-metallicity, high-mass red supergiant progenitor (M ZAMS = 18 M ⊙), which exploded with ∼0.2 × 1051 erg s−1 leaving an ejecta mass of M ej ≈ 5 M ⊙. Significant late-time fallback during the shock propagation phase is also seen in progenitor+explosion models consistent with the light-curve properties. As the faintest short-plateau supernova characterized to date, this event adds to the growing diversity of transitional events between the canonical ∼100 days plateau Type IIP and stripped-envelope events.

Viewing Explosion Models of Type Ia Supernovae through Insights from Terrestrial Cellular Detonation.

The cellular structure is considered to be a key as a criterion in initiation, propagation, and quenching of terrestrial detonation. While a few studies on type Ia supernovae, which are known to involve detonation, have addressed the importance of the cellular structure, further detailed treatment will benefit enhanced understanding of the explosion outcomes. In the present study, we bridge this gap in the astrophysics and engineering fields, focusing on the detonation in a helium-rich white dwarf envelope as the triggering process for the so-called double-detonation model. The cellular structures are quantified via high-resolution two-dimensional simulations. We demonstrate that widely accepted terrestrial-experimental criteria for quenching and initiation of detonation can indeed explain the results of previous hydrodynamic simulations very well. The present study highlights the potential of continuing to apply the insight from terrestrial detonation experiments to astrophysical problems, specifically the long unresolved problem of the explosion mechanism of type Ia supernovae.

Mode analysis and modeling of soliton explosion: based on singular-value decomposition

Mode analysis and modeling of soliton explosion: based on singular-value decomposition

Experimental investigation of explosion hazard from lithium-ion battery thermal runaway effluent gas

Fire and explosion hazards present a serious concern to the widespread adoption of battery technology. This work experimentally investigates the explosion hazards associated with synthesized lithium-ion battery thermal runaway effluent gases (TREG) in an enclosed garage space typical of modern construction in North America. Pressure rise inside the compartment is examined using high-frequency piezoelectric pressure transducers. Data on overpressure and impulse is compared with known ranges for structural damage and bodily injury thresholds and calculation methods for maximum overpressure. Data on time-resolved overpressure are compared with a vented explosion model from literature. These comparisons support that existing models for maximum overpressure and time-resolved pressure rise remain valid for the examined synthesized TREG. Correlations are developed between gas volume and measured impulse and overpressure. An extension of this analysis with values of TREG production from literature supports that pressures measured in these experiments can be generated from ignition of gases released from batteries sized in the range of 3300W⋅h to 80 500W⋅h.

Do not forget the electrons: Extending moderately-sized nuclear networks for multidimensional hydrodynamic codes

Nuclear networks are widely used coupled with hydrodynamical simulations of explosive scenarios to account for the change of nuclear species and energy generation rate due to nuclear reactions. In this way, there is a feedback mechanism between the hydrodynamical state and the nuclear processes. Unfortunately, the timescale of nuclear reactions is orders of magnitude smaller than the dynamical timescale that drives hydrodynamical simulations. Therefore, these nuclear networks are usually very small, reduced in most cases to a dozen elements, especially when simulations are carried out in more than one dimension. We present here an extended nuclear network, with 90 species, designed for being coupled with hydrodynamic simulations, which includes neutrons, protons, electrons, positrons, and the corresponding neutrino and anti-neutrino emission. This network is also coupled with temperature, making it extremely robust and, together with its size, unique of its kind. The inclusion of electron captures on free protons makes the network very appropriate for multidimensional studies of Type Ia supernova explosions, especially when the exploding object is a massive white dwarf. We perform several tests that are relevant to simulate explosive scenarios, such as Type Ia supernovae and core-collapse supernovae. We compare the results of the 90 nuclei network with a standard alpha -chain network with 14 elements to evaluate the differences in the energy generation rate. We also evaluate the relevance of including the electrons in the network in terms of generated yields and how it affects the pressure of a degenerate fluid such as that of white dwarfs. The results obtained with the 90-nuclei network have been verified with a much larger 2000-nuclei network built from REACLIB (WinNet), in terms of nuclear energy generation rate, pressure, and produced yields. The results obtained with the proposed medium-sized network compare fairly well, to a few percent, with those computed with in scenarios reproducing the gross physical conditions of current Type Ia supernova explosion models. In those cases where the carbon and oxygen fuel ignites at high density, the high-temperature plateau typical of the nuclear statistical equilibrium regime is well defined and stable, allowing large integration time steps. We show that the inclusion of electron captures on free protons substantially improves the estimation of the electron fraction of the mixture. Therefore, the pressure is better determined than in networks where electron captures are excluded, which will ultimately lead to more reliable hydrodynamic models. Explosive combustion of helium at low density, occurring near the surface layer of a white dwarf, is also better described with the proposed network, which gives nuclear energy generation rates much closer to than typical reduced alpha networks. A nuclear network with N=90 species, including electrons, aimed at multidimensional calculations of supernova explosions is described and verified. The proposed network is suitable for the study of Type Ia supernova explosions because it provides better values of pressure and electron abundance than other existing networks with smaller or even a similar size but without including electron capture processes.

Two-dimensional models of core-collapse supernova explosions assisted by heavy sterile neutrinos

Two-dimensional models of core-collapse supernova explosions assisted by heavy sterile neutrinos

Flameless venting characteristics and design model of micro-nano PMMA dust explosion

The effects of Fe–Ni foam thickness and dust size on flame propagation, reduced overpressure, and venting efficiency in 30 μm and 150 nm polymethyl methacrylate (PMMA) dust explosions were investigated. The flame quenching mechanism was revealed by coupling the heat transfer and flow of the dust flame within the Fe–Ni foam. It is found that micron dust is more prone to quenching than nano dust, and the differences in the quenching process of micro-nano dust are explained by combining the dust combustion kinetics and the theory of inter-particle heat transfer. The pressure venting mechanism of micro-nano dust was analysed under different thicknesses of Fe–Ni foam, and the thermal expansion effect of the flame passing through the Fe–Ni foam and its flow resistance significantly increased the reduced explosion overpressure. The flow continuity of the micro-nano dust was classified by means of the Knudsen number (Kn), which elucidates the effect of dust size differences on the pressure evolution. A prediction model for the maximum reduced explosion overpressure is proposed based on the explosion pressure venting of micro-nano dust. Changes in vented pressure have a direct impact on the efficiency of flameless venting. Nano-dust has an efficiency of more than 20 % lower than that of micron dust.

Simulation-based personal fatality risk assessment due to the fragmentation hazard

In the military and chemical industry, modeling the fragmentation hazard field is of great significance in conducting the fatality risk assessment and calculating the safety distance for person. Although the ballistic methodology achieves the simulation of fragmentation flight trajectory, the acquisition of accurate initial projection data of fragmentation is a challenge. By coupling continuum-discontinuum element method and particle discrete element method, the fragmentation power algorithm is established, which achieves the integrated simulation of the initial projection data of fragmentation and the flight process of fragmentation. First, continuum-discontinuum element method is adopted to simulate the detonation products-driven fragmentation acceleration process by introducing the explosive detonation model, which achieves the acquisition of initial projection data of fragmentation. Then, the particle discrete element method is adopted to simulate the flight trajectory and power data of fragmentation. Based on the numerical and experimental result, the accuracy of fragmentation power algorithm is verified. In conjunction with the personal vulnerability model, a systematic numerical simulation framework is established to conduct the simulation-based personal fatality risk assessment when the metal-cased munition detonates accidentally, and the results indicate that the personal fatality risk due to the fragmentation becomes severer with the increase of munition curvature.

Characterization of gas explosion shock wave propagation in long straight confined space

Abstract Currently, China is engaged in the construction of urban subterranean areas and the deployment of gas pipelines within these spaces. Nonetheless, the entry of gas into subterranean areas poses a definite threat of leaks and explosions. An explosion triggered by a gas pipeline leak will gravely compromise the underground space’s integrity and significantly affect nearby structures. Consequently, examining the spread properties of gas explosion shock waves in urban subterranean areas is essential. This document utilizes FLACS software to develop an extensive straight confined space gas explosion model, examining the load properties of gas explosion shock waves and deriving the propagation law and distribution patterns of blast shock wave loads across various methane volumes. Gas explosion tests confirm the precision of the numerical model. Findings from the study can supply data on load for comparable safety assessments in underground spaces, enhancing their resilience to explosions.

Simulation and Experimental Study on the Explosion Characteristics of Aluminum Dust in the 5-L Explosion Container

ABSTRACT The CFD software was applied to conduct numerical simulation of the aluminum powder explosion and the study focused on analyzing the pattern of dust diffusion in the 5-L column explosion model containing aluminum powder at a concentration of 700 g/m 3 , and then comparing the simulated pressure change over time with experimental data. The research also examined how different levels of aluminum dust concentration affect the pressure of explosions, the rate at which explosion pressure increases, and the speed of the flame reaching the wall. The findings indicate that, during the pressure time course, the simulation process yields explosion pressure and rate of rise in explosion pressure values for a specific concentration of aluminum dust that deviate by 2% to 19% from experimental results. This suggests that the model utilized in this study possesses a certain level of reliability and it is observed that the variation patterns of explosion pressure and rate of rise in explosion pressure for aluminum dust at different concentrations differ between simulation and experimentation. In the experimentation, at concentrations of 500 g/m 3 and 900 g/m 3 , the explosion pressure and rate of rise both reached their maximum values. Furthermore, the speed of the flame reaching the wall is directly related to the level of concentration.

Carbon monoxide cooling in radiative transfer modelling of supernovae

ABSTRACT Carbon monoxide (CO) emission has been observed in a number of core-collapse supernovae (SNe) and is known to be an important coolant at late times. We have implemented a chemical reaction network in the radiative-transfer code cmfgen to investigate the formation of CO and its impact on SN ejecta. We calculate two 1D SN models with and without CO: a BSG explosion model at one nebular epoch and a full time-sequence (50–300 d) for a red supergiant explosion. In both models, CO forms at nebular times in the dense, inner regions at velocities <2000 km s$^{-1}$ where line emission from CO can dominate the cooling and reduce the local temperature by as much as a factor of 2, weakening emission lines and causing the optical light curve to fade faster. That energy is instead emitted in CO bands, primarily the fundamental band at $\sim 4.5 \mathrm{\mu m}$, which accounts for up to 20 per cent of the total luminosity at late times. However, the non-monotonic nature of the CO cooling function can cause numerical difficulties and introduce multiple temperature solutions. This issue is compounded by the sensitivity of the CO abundance to a few reaction rates, many of which have large uncertainties or disparate values across literature sources. Our results also suggest that, in many SNe, CO-level populations are far from their local thermodynamic equilibrium values. Unfortunately, accurate collisional data, necessary to compute non-local thermodynamic equilibrium populations, are limited to a few transitions.

Pyrolysis kinetics and reaction mechanism studies of 5-Amino-1H-Tetrazole with thermogravimetry/ differential scanning calorimetry/ Fourier transform infrared analysis

5-Amino-1H-Tetrazole (5AT) is extensively utilized in explosives, propellants and pyrotechnics as a high-nitrogen fuel or energetic material. Thermo-analysis is an efficient method to investigate the thermal decomposition characteristics of fuels or energetic materials, aiding in improving the safety and environmental performances of 5AT. In this study, the entire decomposition process of 5AT was explored using TG-DSC (thermogravimetry-differential scanning calorimetry) text. To accurately obtain the complete kinetic triplets, the iso-conversion activation energy for each stage was calculated using three conventional model-free approaches including KAS, Advanced Vyazovkin, and Starink methods, the results show that the activation energy results keep a good agreement by the three methods. Two different model-fitting methods (multiple heating rates CR method and the master-plots Criado method) were also introduced to predict the reaction model and calculate pre-exponential factors based on the iso-conversion activation energy results for the corresponding stages. The similarities and differences of the predicted results from these two different methods were compared, showing almost consistent findings that the first and third stages are controlled by the Fn and Dn model, respectively. Furthermore, the validity and the relationships were effectively verified and corrected based on the obtained kinetic parameters using the kinetic compensation effect, indicating the rationality of the selected kinetic methods and the calculated kinetic parameters for studying the pyrolysis characteristics of 5AT. Additionally, TG-FTIR (thermogravimetry combined with Fourier transform infrared) analysis was also conducted to identify characteristic groups and determine a potential pyrolysis pathway for 5AT. The findings in this paper can be used as input data for thermal safety, combustion, explosion and environmental protection model simulations.