Scaled-distance relationships for close-in detonations

International Journal of Hydrogen Energy, 2011

The use of hydrogen as an energy carrier is going to widen exponentially in the next years. In order to ensure the public acceptance of the new fuel, not only the environmental impact has to be excellent, but also the risk management of its handling and storage must be improved. As a part of modern risk assessment procedure, CFD modeling of the accident scenario development must provide reliable data on the possible pressure loads resulted from explosion processes. The expected combustion regimes can be ranged from slow flames to deflagration-to-detonation transition and even to detonation. In the last case, the importance of the reliability of simulation results is particularly high since detonation is usually considered as a worst case state of affairs. A set of large-scale detonation experiments performed in Kurchatov Institute at RUT facility was selected as benchmark. RUT has typical industry-relevant characteristic dimensions. The CFD codes possibilities to correctly describe detonation in mixtures with different initial and boundary conditions were surveyed. For the modeling, two detonation tests, HYD05 and HYD09, were chosen; both tests were carried out in uniform hydrogen/air mixtures; first one with concentration of 20.0% vol. and the second one with 25.5% vol. In the present exercise three CFD codes using a number of different models were used to simulate these experiments. A thorough inter-comparison between the CFD results, including codes, models and obtained pressure predictions was carried out and reported. The results of this inter comparison should provide a solid basis for the further code development and detonation models' validation thus improving CFD predictive capabilities.

The protective design of civilian engineering structures requires the prediction of air-blast loadings. The scaled-distance charts developed by Kingery and Bulmash, as implemented in US government manuals such as UFC 3-340-02, are typically used to estimate values of incident and reflected overpressures and impulses for design. The Kingery-Bulmash charts reasonably predict these design parameters in the far field but not in the near field, close to the face of the charge. This paper derives predictive equations and scaled-distance charts for incident and reflected overpressures and impulses, and arrival time, based on numerical studies of free-air detonations of spherical charges of TNT.

Journal of Loss Prevention in the Process Industries, 2010

Journal of Loss Prevention in the Process Industries, 2019

Validation of the surrogates at the overall optimal parameter values.. . C.4 Validation of the overall optimised model, separately for each campaign. C.5 Maximum overpressure across the rig for BFETS Phase 2 experiments for the standard and overall optimised model and experimental data.. . C.6 Overpressure-time histories for BFETS Phase 2 experiments for the standard model, overall optimised model and experimental data.. .. .

WIT Transactions on the Built Environment, 2020

Various expressions have been given in the literature for calculating blast wave parameters. Without experimental testing, it is difficult to determine which expression will predict the actual measurements more realistically. In this paper, a statistical analysis of two blast wave parameters, maximum overpressure and pressure-time diagram decay coefficient, was conducted based on field tests of the cylindrical TNT charge free-air detonation. Simple numerical simulation was also performed in order to compare the obtained maximum overpressures with the field test measurements. A comparison of the maximum free-field overpressures provided insights on the influence of the air mesh size as this proved to be a critical parameter. Statistically obtained blast wave decay coefficient and the maximum overpressure was compared with the analytical expressions given by different authors to determine the most appropriate description of experimental tests. Expressions are given depending on the sc...

The modeling of close-in detonations using computational fluid dynamics is common practice in the design of civil structures against blast effects; however in the near field little is known about the accuracy of such modeling techniques. Attacks targeting vulnerabilities in structural systems are a recognized modus operandi in the threat, vulnerability and risk assessments for the design of critical infrastructure assets, and consequently the ability to analyse and design against such attacks is clear. The need to accurately quantify the load acting on the structural element is obvious, particularly where the element is critical to the stability of the structural system. However, it is impossible to directly validate the results of CFD analysis for close-in detonations against experimental data because the incident and reflected overpressures are too high to permit direct measurement using pressure transducers.

The protective design of civilian structures generally requires the prediction of air-blast loadings. The scaled-distance charts developed by Kingery and Bulmash, as implemented in US government manuals such as UFC 3-340-02, are typically used to estimate values of incident and reflected overpressures and impulses for protective design. The Kingery-Bulmash charts reasonably predict these design parameters in the far field but not in the near field, close to the face of the charge, and inside the fireball. This paper presents predictive equations and scaled-distance charts for incident and reflected overpressures and impulses, arrival time, and positive phase duration based on numerical studies of free-air detonations of spherical charges of TNT.

Shock and Vibration, 2018

Results of numerical simulations of explosion events greatly depend on the mesh size. Since these simulations demand large amounts of processing time, it is necessary to identify an optimal mesh size that will speed up the calculation and give adequate results. To obtain optimal mesh sizes for further large-scale numerical simulations of blast wave interactions with overpasses, mesh size convergence tests were conducted for incident and reflected blast waves for close range bursts (up to 5 m). Ansys Autodyn hydrocode software was used for blast modelling in axisymmetric environment for incident pressures and in a 3D environment for reflected pressures. In the axisymmetric environment only the blast wave propagation through the air was considered, and in 3D environment blast wave interaction and reflection of a rigid surface were considered. Analysis showed that numerical results greatly depend on the mesh size and Richardson extrapolation was used for extrapolating optimal mesh size...

International Journal of Protective Structures, 2020

While the current state of blast-resistant design methods is based largely on empirical observations of actual explosive testing or numerical simulations, experimental testing remains the ultimate method for validating blast protection technologies. Field trials for performing systematic experimental studies are exceedingly expensive and inefficient. Conventional blast simulators (shock tubes) enable blast testing to be performed in a safe and controlled laboratory environment but are significantly deficient. The Australian National Facility of Physical Blast Simulation based on the 'Advanced Blast Simulator' concept was established to address the shortcomings of conventional blast simulators (shock tubes). The blast simulator at the National Facility of Physical Blast Simulation is a state-of-the-art design having a test section of 1.5 × 2.0 m with dual-mode driver able of operating with either compressed gas or gaseous detonation modes. The simulator is capable of a range of blast-test configurations such as full-reflection wall targets and diffraction model targets. This article aims to demonstrate the ability of the Advanced Blast Simulator in accurately generating a far-field blast environment suitable for high-precision and repeatable explosion testing of various building components. Blast pressure-time histories generated with the Advanced Blast Simulator are validated against equivalent TNT free-field curves reproduced with Conventional Weapons Effects Program. Numerical models based on Computational Fluid Dynamics were developed in ANSYS FLUENT to accurately characterise and visualise the internal flow environment of the National Facility of Physical Blast Simulation Advanced Blast Simulator. The Computational Fluid Dynamics model was also used to explain experimental observations and to determine density and dynamic pressure information for comparisons with free-field explosion conditions.