“…Hopkinson-Cranz scaling [25] can be used to express the results at a different scale. It should be noted that the effects of blast wave clearing around the target edge have not been included in this analysis [48], however clearing is negligible in the near-field and can be neglected without a significant loss of accuracy [49]. Pressure distribution charts of this nature can be generated for any type and shape of explosive, provided the velocity-radius relationship is known, i.e.…”
Background: The design and analysis of protective systems requires a detailed understanding of, and the ability to accurately predict, the distribution of pressure loads acting on an obstacle following an explosive detonation. In particular, there is a pressing need for accurate characterisation of blast loads in the region very close to a detonation, where even small improvised devices can produce serious structural or material damage. Objective: Accurate experimental measurement of these near-field blast events, using intrusive methods, is demanding owing to the high magnitudes (> 100 MPa) and short durations (< 1 ms) of loading. The objective of this article is to develop a non-intrusive method for measuring reflected blast pressure distributions using image analysis. Methods: This article presents results from high speed video analysis of nearfield spherical PE4 explosive blasts. The Canny edge detection algorithm is used to track the outer surface of the explosive fireball, with the results used to derive a velocity-radius relationship. Reflected pressure distributions are calculated using this velocity-radius relationship in conjunction with the Rankine-Hugoniot jump conditions. Results: The indirectly measured pressure distributions from high speed video are compared with directly measured pressure distributions and are shown to be in good qualitative agreement with respect to distribution of reflected pressures, and in good quantitative agreement with peak reflected pressures (within 10% of the maximum recorded value). Conclusions: The results indicate that it is possible to accurately measure blast loads in the order of 100s MPa using techniques which do not require sensitive recording equipment to be located close to the source of the explosion.
“…Hopkinson-Cranz scaling [25] can be used to express the results at a different scale. It should be noted that the effects of blast wave clearing around the target edge have not been included in this analysis [48], however clearing is negligible in the near-field and can be neglected without a significant loss of accuracy [49]. Pressure distribution charts of this nature can be generated for any type and shape of explosive, provided the velocity-radius relationship is known, i.e.…”
Background: The design and analysis of protective systems requires a detailed understanding of, and the ability to accurately predict, the distribution of pressure loads acting on an obstacle following an explosive detonation. In particular, there is a pressing need for accurate characterisation of blast loads in the region very close to a detonation, where even small improvised devices can produce serious structural or material damage. Objective: Accurate experimental measurement of these near-field blast events, using intrusive methods, is demanding owing to the high magnitudes (> 100 MPa) and short durations (< 1 ms) of loading. The objective of this article is to develop a non-intrusive method for measuring reflected blast pressure distributions using image analysis. Methods: This article presents results from high speed video analysis of nearfield spherical PE4 explosive blasts. The Canny edge detection algorithm is used to track the outer surface of the explosive fireball, with the results used to derive a velocity-radius relationship. Reflected pressure distributions are calculated using this velocity-radius relationship in conjunction with the Rankine-Hugoniot jump conditions. Results: The indirectly measured pressure distributions from high speed video are compared with directly measured pressure distributions and are shown to be in good qualitative agreement with respect to distribution of reflected pressures, and in good quantitative agreement with peak reflected pressures (within 10% of the maximum recorded value). Conclusions: The results indicate that it is possible to accurately measure blast loads in the order of 100s MPa using techniques which do not require sensitive recording equipment to be located close to the source of the explosion.
“…Furthermore, recent research findings give insight on blast loading and clearing effects on finite, non-cylindrical targets, such as in studies by Ballantyne et al (2010), Payne et al (2016), Rigby (2014), and Shin and Whittaker (2019).…”
The design and planning of structural components, such as columns, to resist blast loads is a complex task. Often standard free-field blast loads, specified in design codes or other literature, are used for the analysis of the object. These loads are then further increased or decreased depending on the topology of the surrounding geometry (Mach-Stem), the shape of the impacted object itself, and blast wave reflection. However, most of these research works focus purely on the assessment of the structural components itself, ignoring a complex fluid mechanics phenomenon such as diffraction, which is of particular interest when circular columns are standing next to each other or placed in front of a façade. The article addresses three main topics. First, the article answers the question whether the area behind the column is protected, meaning constituting a shadowed area. We present findings that the close area behind a column is subjected to higher pressure and impulse values as there would be without the column. Hence, the incident pressure sees significant pressure buildup due to diffraction. This pressure buildup is quantified using pressure increase factors and presented together with the accompanying impulse. Second, this pressure buildup is of relevance for realistic design of a façade behind the column, which is not covered in current design codes at all. We discuss relevant parameters in the design process. Third, directly coupled with the assessment of the pressure buildup behind the column due to diffraction is the assessment of pressure and impulse in the area behind the column due to multi-wave reflection at a façade, leading to a significant pressure and impulse scale-up, which might be relevant for design of a column and/or a façade. This article identifies gaps in understanding diffraction and subsequent multi-reflection of blast wave within a structural design framework and provides insights on how to establish safe design accounting for these effects.
“…As an aside, one may note that the speeds are more or less constant for Z > 1 m/kg 1/3 as reported by Qasrawi and Heffernan (2016). For non-planar, close range blast loads, they therefore suggest the use of CFD tools to estimate clearing loads.Figure 6.A plot showing the variation of rarefaction (clearing) wave speed for different scaled blast values (Z, kg/m 1/3 ) along the face of a target as a function of the distance from the centre of the target (Shin and Whittaker, 2019). …”
Section: Direct Loading On a Structurementioning
confidence: 77%
“…For the near-field (0.2 < Z <3 m/kg 1/3 ), Shin and Whittaker (2019) present a comparison of a validated AUTODYN simulation against the simple clearing formulae and demonstrate their inaccuracy in the near-field. In addition to that, using plots of the particle velocity along the front face of the object (Figure 6), they suggest that clearing cannot occur in the near-field as the expansion wave is prevented from travelling inwards.…”
Section: Direct Loading On a Structurementioning
confidence: 99%
“…A plot showing the variation of rarefaction (clearing) wave speed for different scaled blast values (Z, kg/m 1/3 ) along the face of a target as a function of the distance from the centre of the target (Shin and Whittaker, 2019). …”
Blast–obstacle interaction is a complex, multi-faceted problem. Whilst engineering-level tools exist for predicting blast parameters (e.g. peak pressure, impulse and loading duration) in geometrically simple settings, a blast wave is fundamentally altered upon interaction with an object in its path, and hence, the loading parameters are themselves affected. This article presents a comprehensive review of key research in this area. The review is formed of five main parts, each describing: the direct loading of a blast wave on the surface of a finite-sized structure; the modified pressure of the blast wave in the wake region of three main obstacle types – blast walls, obstacles, wall/obstacle hybrids; and finally, a brief description of some methods for predicting loading parameters in such blast–obstacle interaction settings. Key findings relate to the mechanisms governing blast attenuation, for example, diffraction, reflection (diverting away from the target structure), expansion/volume increase, vortex creation/growth, as well as obstacle properties influencing these, such as porosity (blockage ratio), obstacle shape, number of obstacles/rows, arrangement and surface roughness.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
