Particle recycling in volcanic plumes

Veitch, Graham; Woods, Andrew W.

doi:10.1007/s00445-001-0180-3

Cited by 21 publications

(16 citation statements)

References 21 publications

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“…Further development of volcanic plume models have included the influence of atmospheric stratification and humidity (Woods, 1993;Glaze and Baloga, 1996), the effect of crosswind (Bursik, 2001), loss and re-entrainment of solid particles from plume margins (Woods and Bursik, 1991;Veitch and Woods, 2002), wet aggregation and transient effects (Scase, 2009;Woodhouse et al, 2015). However, one-dimensional models strongly rely on the self-similarity hypothesis, whose validity cannot be experimentally ascertained for volcanic eruptions.…”

Section: Dusty-gas Modeling Of Volcanic Plumesmentioning

confidence: 99%

ASHEE-1.0: a compressible, equilibrium–Eulerian model for volcanic ash plumes

2016

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Abstract.A new fluid-dynamic model is developed to numerically simulate the non-equilibrium dynamics of polydisperse gas-particle mixtures forming volcanic plumes. Starting from the three-dimensional N-phase Eulerian transport equations for a mixture of gases and solid dispersed particles, we adopt an asymptotic expansion strategy to derive a compressible version of the first-order non-equilibrium model, valid for low-concentration regimes (particle volume fraction less than 10 −3 ) and particle Stokes number (St -i.e., the ratio between relaxation time and flow characteristic time) not exceeding about 0.2. The new model, which is called ASHEE (ASH Equilibrium Eulerian), is significantly faster than the N-phase Eulerian model while retaining the capability to describe gas-particle non-equilibrium effects. Direct Numerical Simulation accurately reproduces the dynamics of isotropic, compressible turbulence in subsonic regimes. For gas-particle mixtures, it describes the main features of density fluctuations and the preferential concentration and clustering of particles by turbulence, thus verifying the model reliability and suitability for the numerical simulation of highReynolds number and high-temperature regimes in the presence of a dispersed phase. On the other hand, Large-Eddy Numerical Simulations of forced plumes are able to reproduce the averaged and instantaneous flow properties. In particular, the self-similar Gaussian radial profile and the development of large-scale coherent structures are reproduced, including the rate of turbulent mixing and entrainment of atmospheric air. Application to the Large-Eddy Simulation of the injection of the eruptive mixture in a stratified atmosphere describes some of the important features of turbulent volcanic plumes, including air entrainment, buoyancy reversal and maximum plume height. For very fine particles (St → 0, when non-equilibrium effects are negligible) the model reduces to the so-called dusty-gas model. However, coarse particles partially decouple from the gas phase within eddies (thus modifying the turbulent structure) and preferentially concentrate at the eddy periphery, eventually being lost from the plume margins due to the concurrent effect of gravity. By these mechanisms, gas-particle non-equilibrium processes are able to influence the large-scale behavior of volcanic plumes.

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Section: Dusty-gas Modeling Of Volcanic Plumesmentioning

confidence: 99%

ASHEE-1.0: a compressible, equilibrium–Eulerian model for volcanic ash plumes

2016

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“…For example, Sparks et al [1991] developed a theoretical model for sedimentation from radially spreading gravity currents resulting from vertically rising sediment‐laden plumes and compared it with experimental data, with environmental applications such as volcanic ejecta and black smokers in mind. Veitch and Woods [2000, 2002] used a plume sedimentation model in addition to experimental observations to simulate particle recycling and oscillations in the particle‐laden, buoyant plumes resulting from volcanic eruptions.…”

Section: Sedplume Modelmentioning

confidence: 99%

Modeling glacial meltwater plume dynamics and sedimentation in high-latitude fjords

Mugford

Dowdeswell

2011

J. Geophys. Res.

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[1] A model, SedPlume, has been developed to simulate marine sediment deposited by glacial meltwater plumes emerging from tidewater glaciers. Turbid meltwater emerging from beneath a glacier into a fjord rises as a buoyant forced plume due to density contrasts with the ambient fjord water. SedPlume assumes that meltwater discharge flows at a constant rate for long enough periods that the plume reaches a steady state. Entrainment of ambient fluid into the turbulent plume is assumed to occur at a rate proportional to the local velocity of the plume. Plume motion is considered in two dimensions: one horizontal dimension (perpendicular to the glacier front) and the vertical dimension. An integral model is formulated for the conservation equations of volume, momentum, buoyancy, and sediment flux along the path of a turbulent plume injected into stably stratified ambient fluid. Sedimentation occurs from the plume when the radial component of the sediment fall velocity exceeds the entrainment velocity. When the plume reaches the surface, it is treated as a radially spreading surface gravity current, for which exact solutions exist for the sediment deposition rate. Flocculation of silt and clay particles is modeled using empirical measurements of particle settling velocities in fjords to adjust the settling velocity of finegrained sediments. SedPlume has been applied to McBride Inlet, Alaska, a temperate glaciated fjord where the majority of sedimentation originates from meltwater sources. SedPlume produces rates and patterns of sedimentation in good agreement with observations, with calculated peak ice-proximal annual sedimentation rates of approximately 22 m yr −1 .Citation: Mugford, R. I., and J. A. Dowdeswell (2011), Modeling glacial meltwater plume dynamics and sedimentation in highlatitude fjords,

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“…Theoretical studies of eruption plumes that consider alternations of fall and PDC activity (e.g., Neri and Dobran 1994;Kaminski and Jaupart 2001;Veitch and Woods 2002) arrive at models that permit oscillations of eruptive styles over time scales of several hundreds to thousands of seconds. Our timing data (above) suggest that the Novarupta plume did not switch styles as such, but, instead, maintained simultaneously buoyant and nonbuoyant states of different fractions (Fig.…”

Section: Implications For Eruption Column Modelsmentioning

confidence: 99%

Complex proximal deposition during the Plinian eruptions of 1912 at Novarupta, Alaska

Houghton

Wilson

Fierstein

et al. 2004

Bulletin of Volcanology

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Proximal (<3 km) deposits from episodes II and III of the 60-h-long Novarupta 1912 eruption exhibit a very complex stratigraphy, the result of at least four transport regimes and diverse depositional mechanisms. They contrast with the relatively simple stratigraphy (and inferred emplacement mechanisms) for the previously documented, better known, medial-distal fall deposits and the Valley of Ten Thousand Smokes ignimbrite. The proximal products include alternations and mixtures of both locally and regionally dispersed fall ejecta, and numerous thin complex deposits of pyroclastic density currents (PDCs) with no regional analogs. The locally dispersed component of the fall deposits forms sectorconfined wedges of material whose thicknesses halve radially from and concentrically about the vent over distances of 100-300 m (cf. several kilometers for the medial-distal fall deposits). This locally dispersed fall material (and many of the associated PDC deposits) is rich in andesitic and banded pumices and richer in shallow-derived wall-rock lithics in comparison with the coeval medial fall units of almost entirely dacitic composition. There are no marked contrasts in grain size in the near-vent deposits, however, between locally and widely dispersed beds, and all samples of the proximal fall deposits plot as a simple continuation of grain size trends for medial-distal samples. Associated PDC deposits form a spectrum of facies from fines-poor, avalanched beds through thin-bedded, landscape-mantling beds to channelized lobes of pumice-block-rich ignimbrite. The origins of the Novarupta near-vent deposits are considered within a spectrum of four transport regimes: (1) sustained buoyant plume, (2) fountaining with co-current flow, (3) fountaining with counter-current flow, and (4) direct lateral ejection. The Novarupta deposits suggest a model where buoyant, stable, regime-1 plumes characterized most of episodes II and III, but were accompanied by transient and variable partitioning of clasts into the other three regimes. Only one short period of vent blockage and cessation of the Plinian plume occurred, separating episodes II and III, which was followed by a single PDC interpreted as an overpressured "blast" involving direct lateral ejection. In contrast, regimes 2 and 3 were reflected by spasmodic sedimentation from the margins of the jet and perhaps lower plume, which were being strongly affected by short-lived instabilities. These instabilities in turn are inferred to be associated with heterogeneities in the mixture of gas and pyroclasts emerging from the vent. Of the parameters that control explosive eruptive behavior, only such sudden and asymmetrical changes in the particle concentration could operate on time scales sufficiently short to explain the rapid changes in the proximal 1912 products.

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Particle recycling in volcanic plumes

Cited by 21 publications

References 21 publications

ASHEE-1.0: a compressible, equilibrium–Eulerian model for volcanic ash plumes

ASHEE-1.0: a compressible, equilibrium–Eulerian model for volcanic ash plumes

Modeling glacial meltwater plume dynamics and sedimentation in high-latitude fjords

Complex proximal deposition during the Plinian eruptions of 1912 at Novarupta, Alaska

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