“…This means that for closer stand-off distances, a cylinder with larger diameter is required to achieve good attenuation by disrupting the flow-field downstream. So in addition to the others, the distance to target measure d t is a significant parameter as it regulates the wave detachment process (Christiansen and Bogosian 2012; Dey et al, 2020; Hahn et al, 2021). Figure 11.A scatter plot of energy-equivalent specific impulse ratio as a function of obstacle scaled distance Z do for cylinder diameters of 12, 16, 20 and 24 cm.…”
Section: Resultsmentioning
confidence: 99%
“…Two-dimensional numerical modelling, which only takes into account diffraction from the top edge, was carried out by Dey et al (2020). The differences between the disturbed flow and the free-field scenario were found to be less than 5%.…”
Section: Literature Review and Theoretical Considerationsmentioning
Obstructing the passage of blast waves is an effective method of mitigating blast pressures downstream of the obstacle. To this end, the interaction between a blast wave and a simplified structural shape, such as a cylinder, has been widely investigated to understand the complex flow pattern that ensues around the obstacle. The patterns include the interference zones of the incident wave, the diffracted wave, and other secondary waves in the downstream region. Such zones are responsible for causing significant modifications to the blast wave parameters. This research aims to identify and study the factors that serve to mitigate the resulting blast loads downstream of a cylindrical obstacle – both on the ground, and on a rigid wall target that the obstacle is aiming to protect. Inputs from this numerical study are also used to develop a fast-running predictive method based on an artificial neural network (ANN) model. It was found that the size of the cylinder, the strength of the blast wave, the position of the cylindrical obstruction, and the target length, all have remarkable effects on the development of the complex flow-field downstream, and on the impulse mitigation on a reflective target. A number of key mitigation mechanisms are identified, namely shadowing and interference, and their origins and significance are discussed. An ANN model trained using scaled input parameters could successfully predict impulse values on such a reflective target. Using this model to predict the response of previously unseen configurations (for the ANN) gave excellent correlation, thereby demonstrating the high fidelity of this fast-running tool, and its ability to predict the effectiveness of various wave-cylinder interactions in mitigating blast loading.
“…This means that for closer stand-off distances, a cylinder with larger diameter is required to achieve good attenuation by disrupting the flow-field downstream. So in addition to the others, the distance to target measure d t is a significant parameter as it regulates the wave detachment process (Christiansen and Bogosian 2012; Dey et al, 2020; Hahn et al, 2021). Figure 11.A scatter plot of energy-equivalent specific impulse ratio as a function of obstacle scaled distance Z do for cylinder diameters of 12, 16, 20 and 24 cm.…”
Section: Resultsmentioning
confidence: 99%
“…Two-dimensional numerical modelling, which only takes into account diffraction from the top edge, was carried out by Dey et al (2020). The differences between the disturbed flow and the free-field scenario were found to be less than 5%.…”
Section: Literature Review and Theoretical Considerationsmentioning
Obstructing the passage of blast waves is an effective method of mitigating blast pressures downstream of the obstacle. To this end, the interaction between a blast wave and a simplified structural shape, such as a cylinder, has been widely investigated to understand the complex flow pattern that ensues around the obstacle. The patterns include the interference zones of the incident wave, the diffracted wave, and other secondary waves in the downstream region. Such zones are responsible for causing significant modifications to the blast wave parameters. This research aims to identify and study the factors that serve to mitigate the resulting blast loads downstream of a cylindrical obstacle – both on the ground, and on a rigid wall target that the obstacle is aiming to protect. Inputs from this numerical study are also used to develop a fast-running predictive method based on an artificial neural network (ANN) model. It was found that the size of the cylinder, the strength of the blast wave, the position of the cylindrical obstruction, and the target length, all have remarkable effects on the development of the complex flow-field downstream, and on the impulse mitigation on a reflective target. A number of key mitigation mechanisms are identified, namely shadowing and interference, and their origins and significance are discussed. An ANN model trained using scaled input parameters could successfully predict impulse values on such a reflective target. Using this model to predict the response of previously unseen configurations (for the ANN) gave excellent correlation, thereby demonstrating the high fidelity of this fast-running tool, and its ability to predict the effectiveness of various wave-cylinder interactions in mitigating blast loading.
“…Using three poles (one ∼64 mm and two ∼50 mm diameter) in a triangular arrangement, with the bigger pole facing the explosion and the smaller ones behind it, the reduction in overpressure and impulse was enhanced twofold. Dey et al (2020) used ANSYS Fluent to study the pressure field around generic obstacles: sphere; cone; and cylinder, all having equal frontal dimension and overall length. They found that the strongest initial wave reflection was seen for the cylinder, followed by the sphere and then the cone.…”
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.
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