On the systematics of particle velocity histories in the shock-to-detonation transition regime

James, H. R.; Lambourn, B. D.

doi:10.1063/1.2354416

Cited by 33 publications

(23 citation statements)

References 7 publications

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“…Point 1 suggested that each explosive particle was reacting independently of its neighbours, which led to the simple analytic model CIM [4]. The reactive burn model, CREST, followed from Point 3 and gained credibility from both it's success in predicting shock initiation and detonation phenomena and the Overall Conclusion of the analysis [3] that: "At least to first order, the reaction rate is solely dependent on two factors, shock strength and the time along a particle path since the shock passed. "…”

Section: Summary Of Evidencementioning

confidence: 99%

“…Analysis of the experimental results [3,4] shows that: 1. The time of peak particle velocity initially moves away from the shock, then runs parallel (Δt ~ constant) to the shock, before it begins to accelerate like a normal hydrodynamic pulse, to catch up the shock.…”

Section: Summary Of Evidencementioning

confidence: 99%

“…8. If scaled velocities U=(u(t)-u Shk )/Δu are plotted against scaled times T=(t-t Shk )/Δt for PBX9501 [3] and PBX9502 ( Fig. 3), then the shape is independent of shock strength to well beyond peak velocity.…”

Section: Summary Of Evidencementioning

confidence: 99%

“…The aim of this paper is to test the Overall Conclusion in [3] by using theoretical reactive hydrodynamics to find the overall form of the reaction rate, given the observed scaling rules for particle velocity histories. Because it is a simpler case, the main emphasis is on the PBX9502 results.…”

Section: Theoretical Assessmentmentioning

confidence: 99%

“…The conclusion of the analysis [3] was that, at least to first order, reaction rate depends on shock strength and time along a particle path.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

The relation between reaction rate and shock strength-A possible second order improvement to the crest reactive burn model

Lambourn

James

2012

AIP Conference Proceedings

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Section: Summary Of Evidencementioning

confidence: 99%

Section: Summary Of Evidencementioning

confidence: 99%

Section: Summary Of Evidencementioning

confidence: 99%

Section: Theoretical Assessmentmentioning

confidence: 99%

“…The conclusion of the analysis [3] was that, at least to first order, reaction rate depends on shock strength and time along a particle path.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

The relation between reaction rate and shock strength-A possible second order improvement to the crest reactive burn model

Lambourn

James

2012

AIP Conference Proceedings

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Modelling the Fluctuations of Reactive Shock Waves in Heterogeneous Solid Explosives as Stochastic Processes

Kittell

Yarrington

Lechman

et al. 2019

Propellants Explo Pyrotec

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While current phenomenological burn models are useful for describing the average or bulk reactive flow behaviour of heterogeneous explosives, one fundamental weakness inherent to these models is the loss of detailed microstructural information at the scale of the calculation. In order to include the effects of the microstructure, and in particular the underlying material heterogeneities that influence the build‐up to detonation, a new paradigm is put forth for modelling sub‐grid, reaction‐induced fluctuations (i. e. “hot spots”) at the continuum level. This modelling approach assumes that the reaction rate is stochastic, rather than deterministic, and it uses Langevin‐type equations with a mathematical framework built upon Itô calculus and Lambourn's CIM model for shocked heterogeneous explosives. This approach follows directly from our previous letter, Ref. [1], and is inspired by the probability density function (pdf) methods used in turbulent reactive flows. Here, the stochastic burn model is derived, implemented, and exercised far beyond what has been shown in previous work. New hydrocode simulation results demonstrate the role of stochastic fluctuations during shock initiation; these fluctuations are approximated by collections of discrete particles, that evolve with drift (i. e. deterministic) and diffusion (i. e. stochastic) coefficients. Additionally, the particle values are propagated and averaged to calculate the heat release, yield strength, and material impedance in each computational cell. Hydrocode simulation results further show how the fluctuating hot spot energy may or may not be transmitted to the wave front, and result in a detonation wave‐like structure. The fundamental stochastic nature of this model permits simulations to have varying outcomes with the same initial conditions; this allows for go/no‐go estimation (e. g., marginal or failed detonations), which might possibly be calibrated using the statistical distributions from real materials. Mesoscale calculations of shocked heterogeneous explosives also show that these fluctuations are physically justified (i. e., Ref. [2]), and it is hypothesized that the pdf functions provide a link between the meso(grain) and continuum scales for practical engineering calculations. Thus, our approach is a paradigm shift for building efficient, reduced order continuum burn models, that represent the sub‐grid stochastic behaviour of shocked heterogeneous solid explosives.

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Short Pulse Initiation of an RDX‐Based Explosive Using Large Diameter Flyer‐Plate Impacts

Neel¹,

Sable²

2020

Propellants Explo Pyrotec

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Ten impact experiments are presented that probe the initiation behavior of an RDX-based explosive. The explosive pellets were impacted by thin aluminum impactors supported by low-impedance polymers, thereby subjecting the pellets to short duration shocks. Impact conditions were used to determine impact tilt, pulse pressure and duration, sample transit time, and whether or not a detonation occurred. Exploding Foil Initiator (EFI) launchers were used as a baseline for evaluating the technique, and it was found that the present technique addresses multiple shortcomings of EFI-based systems. The aluminum foil allowed impacts with pressure durations of 70-80 ns, resulting in input conditions closely matching those of EFI-based systems. The thicker aluminum plate impactors resulted in pulse durations of approximately 600 ns and allowed access to a previously inaccessible region of the initiation curve. Initiation thresholds were bracketed using both impactors, and the data is compared with complementary initiation data from EFI-based systems with good agreement. Based on the results and closely related work, a novel, physically-based criterion is proposed to allow the initiation curve to be predicted based on the explosive's unreacted equation of state and sustained-pulse, shock-to-detonation run distance (the "Pop-plot"), giving a physical basis for previously published observations. Finally, the criterion is applied to the data available to propose a relationship between pressure, pulse duration, and run distance, suggesting that input pulse durations of 50-100 % higher than the critical condition should be applied to approximate the run distance of a sustained pulse.

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On the systematics of particle velocity histories in the shock-to-detonation transition regime

Cited by 33 publications

References 7 publications

The relation between reaction rate and shock strength-A possible second order improvement to the crest reactive burn model

The relation between reaction rate and shock strength-A possible second order improvement to the crest reactive burn model

Modelling the Fluctuations of Reactive Shock Waves in Heterogeneous Solid Explosives as Stochastic Processes

Short Pulse Initiation of an RDX‐Based Explosive Using Large Diameter Flyer‐Plate Impacts

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