Abstract
To better understand the complex dynamics and physics associated with the rapid expansion of the detonation product fireball following an explosion, it is imperative to have a full description of its associated velocity field. Typical experimental techniques rely on simple single-point measurements captured from pressure transducers or Hopkinson pressure bars. In this technical design note, we aim to improve the current state-of-the-art by introducing a means to determine full velocity fields from high-speed video using optical flow tracking velocimetry. We demonstrate the significance of this method from our results by comparing velocity fields derived from high-speed video and a validated numerical model of the same case. A wider use of this technique will allow researchers to elucidate spatial and temporal features of explosive detonations, which could not be obtained thus far using single-point measurements.
Highlights
When an explosive detonates, it converts into a high-pressure, high-energy gas that rapidly expands and displaces the surrounding air at supersonic speeds, causing a blast wave to form
To better understand the complex dynamics and physics associated with the rapid expansion of the detonation product fireball following an explosion, it is imperative to have a full description of its associated velocity field
In the first four rows of figure 1 we show the magnitude of the velocity fields derived from the high-speed video
Summary
It converts into a high-pressure, high-energy gas that rapidly expands and displaces the surrounding air at supersonic speeds, causing a blast wave to form. In order to provide adequate and efficient protective systems against blast loading, it is of critical importance that the evolving properties of the explosive products and the emerging blast wave are well characterised and understood. In the region close to the source of the explosion, blast pressures are in the order of several hundreds of megapascals Kinney and Graham (1985), and direct experimental measurement is challenging Rigby et al (2015). Research into high explosives (and our ability to rigorously validate new numerical modelling approaches for this purpose), is dependent on our ability to provide indirect, yet accurate measurements and quantification of blast parameters. In order to experimentally interrogate the physics of near-field explosions, we often rely on pressure transducers that provide single-point temporal data, which can be used to either validate computer models or to provide limited scientific insight.
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