On the propagation and multiple reflections of a blast wave travelling through a dusty gas in a closed box

Lappa, Marcello; Drikakis, Dimitris; Kokkinakis, Ioannis

doi:10.1063/1.4979066

Cited by 10 publications

(14 citation statements)

References 30 publications

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“…Along these lines, we start from the simple remark that in the present case, the density ρ p of the particles is much larger than the density ρ g of the surrounding gas ( = ρ p /ρ g >> 1, which implies that the inertia of the former cannot be neglected). Moreover, the particles have a characteristic size very small with respect to the length scale of the considered physical domain, which leads to the need to account for viscous effects at the particle length scale (Lappa et al [2]).…”

Section: Particle Trackingmentioning

confidence: 99%

“…On the one hand, such size is so small that viscous effects cannot be neglected, on the other hand,, however, it is not infinitesimal, which makes a representation based on the concepts of point-like particles with negligible mass too inaccurate (as explained above, a physically accurate model must take into account the particle inertia). A first relevant quantity leading to cast the problem in a relevant theoretical framework is the so-called particle relaxation (or aerodynamic response) time (), which in the literature ( [2]) is generally defined as:…”

Section: Particle Trackingmentioning

confidence: 99%

“…In particular, the gas velocity V appearing in Eqs. (10) and (11) has been "reconstructed" at each particle location from the surrounding grid locations by means of a proper interpolation scheme (Lappa et al [2]).…”

Section: Time Integrationmentioning

confidence: 99%

“…The number of points along the horizontal direction has been scaled accordingly (2400 points per meter). The overall mathematical framework was validated by Lappa et al [2]. The related details are not reported here to avoid duplications and save space.…”

Section: Time Integrationmentioning

confidence: 99%

“…Many environmental and industrial processes involve the interaction between coherent flow structures (e.g., a jet) and particles, bubbles or droplets. These systems can generally involve a relatively wide range of characteristic length and time scales (with regard to both the flow and the motion of particles; Scala [1]; Lappa et al [2]). Given the number and variety of relevant natural or environmental processes and potential applications in technology, providing an exhaustive description of this subject is not as straightforward as one would imagine.…”

Section: Introductionmentioning

confidence: 99%

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High velocity infrared thermography and numerical trajectories of solid particles in compressible gas flow

et al. 2019

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The use of High Velocity Infrared Thermography as a valuable alternative to other existing techniques for the visualisation and tracking of solid particles transported by a gas jet has been assessed by considering different situations in terms of problem characteristic numbers (jet Reynolds and Mach numbers and Particle Stokes and gravitational Froude numbers). Particles paths have also been calculated by means of a hybrid Eulerian-Lagrangian technique under the intent to cross-validate the two (experimental and numerical) approaches. The results indicate that such a strategy is robust and sufficiently flexible to be used in relatively wide regions of the space of parameters. Experiments have clearly demonstrated that thermography can properly capture particle dynamics with a level of detail comparable to that provided by simulations. Computations have proved to be valuable on their own by allowing the explorations of regions of the parameters space otherwise out of reach. Different tests have been conducted considering both isolated particles and "swarms". We show that the observed dynamics are induced by the delicate interplay of different effects, including inertial, gravitational and eventually "lift" contributions produced by a nonperfect horizontal orientation of the jet or other uncertainties (such as those due to a non mono-sized set of particles).

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Section: Particle Trackingmentioning

confidence: 99%

Section: Particle Trackingmentioning

confidence: 99%

Section: Time Integrationmentioning

confidence: 99%

Section: Time Integrationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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High velocity infrared thermography and numerical trajectories of solid particles in compressible gas flow

et al. 2019

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On the multiplicity and symmetry of particle attractors in confined non-isothermal fluids subjected to inclined vibrations

Lappa

2017

International Journal of Multiphase Flow

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We investigate the relationship between the motion of solid particles and related clustering dynamics under the combined influence of a large-scale convective flow and vibrations-induced small-scale displacements in microgravity conditions. Such a study is motivated by the relatively recent discovery of a new class of particle attractors for which thermal and inertial effects play a fundamental role whereas particle-to-particle interactions are not essential. The key aim is to expand the set of predictive links between flow properties and particle behavior identified in the author’s earlier work (Phys. Fluids, 26(9), 093301, 2014). Insights are sought from consideration of two archetypal settings, both originating from the classical problem of a differentially heated cubic cavity, which in one case is subjected to vibrations contained in a plane parallel to one of the insulated walls (i.e. having a component in the direction parallel to the temperature gradient) and in the other experiences periodic accelerations arbitrarily oriented in space. The present study reveals that the multiplicity of the particle attractors, previously thought to be a universal number (N=2 according to earlier studies), is not a constant. The two distinct particle attractors seen in past investigations can undergo “coalescence” in some cases and exist as a single attractor over a relatively wide range of conditions. Moreover, in addition to the ellipsoid, cylinders and conical surfaces, other shapes of the attractors become possible when the vibrations are inclined with respect to the adiabatic walls, such as amphora-like or saddle-horse paraboloid structures

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Numerical study on dusty shock reflection over a double wedge

2018

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The dusty shock reflection over a double wedge with different length scales is systematically studied using an adaptive multi-phase solver. The non-equilibrium effect caused by the particle relaxation is found to significantly influence the shock reflection process. Specifically, it behaves differently for double wedges with different length scales of the first wedge L1. For a double wedge with L1 relatively longer than the particle relaxation length λ, the equilibrium shock dominates the shock reflection and seven typical reflection processes are obtained, which is similar to the pure gas counterpart. For a double wedge with L1 shorter than λ, the non-equilibrium effect manifests more evidently, i.e., three parts of the dusty shock system including the frozen shock, the relaxation zone, and the equilibrium shock together dominate the reflection process. As a result, the shock reflection is far more complicated than the pure gas counterpart and eleven transition processes are found under various wedge angles. These findings give a complete description of all possible processes of dusty shock reflection over a double wedge and may be useful for better understanding the non-equilibrium shock reflection over complex structures.

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On the propagation and multiple reflections of a blast wave travelling through a dusty gas in a closed box

Cited by 10 publications

References 30 publications

High velocity infrared thermography and numerical trajectories of solid particles in compressible gas flow

High velocity infrared thermography and numerical trajectories of solid particles in compressible gas flow

On the multiplicity and symmetry of particle attractors in confined non-isothermal fluids subjected to inclined vibrations

Numerical study on dusty shock reflection over a double wedge

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