The influence of shape on the atmospheric settling velocity of volcanic ash particles

Wilson, Lionel; Huang, T. C.

doi:10.1016/0012-821x(79)90179-1

Cited by 233 publications

(235 citation statements)

References 16 publications

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“…The axis lengths a, b and c used to calculate the shape factor of Wilson and Huang (1979) were deliberately defined as (a) the longest particle dimension, (b) the longest dimension perpendicular to (a), and (c) the dimension perpendicular to both (a) and (b) to stick to the author's definition. This method, however, is subject to controversy and more recent texts prefer measuring (b) and (c) based on the smallest projected area, and (a) perpendicular to (b) and (c) (s. Blott and Pye, 2008 for a review).…”

Section: Quantification Of Morphological Featuresmentioning

confidence: 99%

“…Using the standard definition of circularity (P circle /P particle ), the shape factor corresponds to the product of sphericity and circularity values. g Defined as (b + c)/2a (Wilson and Huang, 1979). fully quantifiable.…”

Section: Spatial Resolution and Detectabilitymentioning

confidence: 99%

“…In terms of aerodynamics, shape has a direct impact on the drag forces acting on rising and falling particles (Stringham et al, 1969;Bursik, 1989;Ganser, 1993;Mitchell, 1996;Chhabra et al, 1999;Mele et al, 2011;Dellino et al, 2012), which in turn influence the settling velocity (Wilson and Huang, 1979;Coltelli et al, 2008;Alfano et al, 2011), the atmospheric residence time (Riley et al, 2003), and the transport distance and dispersal of tephra (Sparks et al, 1997;Scollo et al, 2008). The aerial behavior of ash is also indirectly influenced by the surface-to-volume ratio, which affects the propensity of particles to form aggregates, both in dry and wet environments (e.g.…”

Section: Introduction and Previous Workmentioning

confidence: 99%

“…These flaws have been corrected in most of the recent numerical models (e.g. Macedonio et al, 2005;Costa et al, 2006;Barsotti et al, 2008;Schwaiger et al, 2012) through the integration of a particle shape factor (Wilson and Huang, 1979;Ganser, 1993;Dellino et al, 2005) accounting for the non-spherical character of volcanic ash. The result is a significant improvement in the modeling of tephra transport and dispersal, which underlines the need for reliable techniques to fully characterize the shape of volcanic ash particles.…”

Section: Introduction and Previous Workmentioning

confidence: 99%

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High-resolution 3D analyses of the shape and internal constituents of small volcanic ash particles: The contribution of SEM micro-computed tomography (SEM micro-CT)

Vonlanthen

Rausch

Ketcham

et al. 2015

Journal of Volcanology and Geothermal Research

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The morphology of small volcanic ash particles is fundamental to our understanding of magma fragmentation, and in transport modeling of volcanic plumes and clouds. Until recently, the analysis of 3D features in small objects (b250 μm) was either restricted to extrapolations from 2D approaches, partial stereo-imaging, or CT methods having limited spatial resolution and/or accessibility. In this study, an X-ray computed-tomography technique known as SEM micro-CT, also called 3D X-ray ultramicroscopy (3D XuM), was used to investigate the 3D morphology of small volcanic ash particles (125-250 μm sieve fraction), as well as their vesicle and microcrystal distribution. The samples were selected from four stratigraphically well-established tephra layers of the Meerfelder Maar (West Eifel Volcanic Field, Germany). Resolution tests performed on a Beametr v1 pattern sample along with Monte Carlo simulations of X-ray emission volumes indicated that a spatial resolution of 0.65 μm was obtained for X-ray shadow projections using a standard thermionic SEM and a bulk brass target as X-ray source. Analysis of a smaller volcanic ash particle (64-125 μm sieve fraction) showed that features with volumes N 20 μm 3 (~3.5 μm in diameter) can be successfully reconstructed and quantified. In addition, new functionalities of the Blob3D software were developed to allow the particle shape factors frequently used as input parameters in ash transport and dispersion models to be calculated. This study indicates that SEM micro-CT is very well suited to quantify the various aspects of shape in fine volcanic ash, and potentially also to investigate the 3D morphology and internal structure of any object b 0.1 mm 3 .

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Section: Quantification Of Morphological Featuresmentioning

confidence: 99%

Section: Spatial Resolution and Detectabilitymentioning

confidence: 99%

Section: Introduction and Previous Workmentioning

confidence: 99%

Section: Introduction and Previous Workmentioning

confidence: 99%

See 2 more Smart Citations

High-resolution 3D analyses of the shape and internal constituents of small volcanic ash particles: The contribution of SEM micro-computed tomography (SEM micro-CT)

Vonlanthen

Rausch

Ketcham

et al. 2015

Journal of Volcanology and Geothermal Research

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“…Several empirical fits exist for drag coefficients of spherical and non-spherical particles (e.g. Wilson and Huang, 1979;Arastoopour et al, 1982;Ganser, 1993;Dellino et al, 2005). In particular, Ganser (1993) gave a fit valid over a wide range of particle sizes and shapes covering the spectrum of volcanic particles considered in volcanic column models (lapilli and ash):…”

mentioning

confidence: 99%

FPLUME-1.0: An integral volcanic plume model accounting for ash aggregation

2016

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Abstract. Eruption source parameters (ESP) characterizing volcanic eruption plumes are crucial inputs for atmospheric tephra dispersal models, used for hazard assessment and risk mitigation. We present FPLUME-1.0, a steady-state 1-D (one-dimensional) cross-section-averaged eruption column model based on the buoyant plume theory (BPT). The model accounts for plume bending by wind, entrainment of ambient moisture, effects of water phase changes, particle fallout and re-entrainment, a new parameterization for the air entrainment coefficients and a model for wet aggregation of ash particles in the presence of liquid water or ice. In the occurrence of wet aggregation, the model predicts an effective grain size distribution depleted in fines with respect to that erupted at the vent. Given a wind profile, the model can be used to determine the column height from the eruption mass flow rate or vice versa. The ultimate goal is to improve ash cloud dispersal forecasts by better constraining the ESP (column height, eruption rate and vertical distribution of mass) and the effective particle grain size distribution resulting from eventual wet aggregation within the plume. As test cases we apply the model to the eruptive phase-B of the 4 April 1982 El Chichón volcano eruption (México) and the 6 May 2010 Eyjafjallajökull eruption phase (Iceland). The modular structure of the code facilitates the implementation in the future code versions of more quantitative ash aggregation parameterization as further observations and experiment data will be available for better constraining ash aggregation processes.

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Modeling ash fall distribution from a Yellowstone supereruption

Mastin

Eaton

Lowenstern

2014

Geochem Geophys Geosyst

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We used the volcanic ash transport and dispersion model Ash3d to estimate the distribution of ashfall that would result from a modern-day Plinian supereruption at Yellowstone volcano. The simulations required modifying Ash3d to consider growth of a continent-scale umbrella cloud and its interaction with ambient wind fields. We simulated eruptions lasting 3 days, 1 week, and 1 month, each producing 330 km 3 of volcanic ash, dense-rock equivalent (DRE). Results demonstrate that radial expansion of the umbrella cloud is capable of driving ash upwind (westward) and crosswind (N-S) in excess of 1500 km, producing more-or-less radially symmetric isopachs that are only secondarily modified by ambient wind. Deposit thicknesses are decimeters to meters in the northern Rocky Mountains, centimeters to decimeters in the northern Midwest, and millimeters to centimeters on the East, West, and Gulf Coasts. Umbrella cloud growth may explain the extremely widespread dispersal of the 640 ka and 2.1 Ma Yellowstone tephra deposits in the eastern Pacific, northeastern California, southern California, and South Texas.

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The influence of shape on the atmospheric settling velocity of volcanic ash particles

Cited by 233 publications

References 16 publications

High-resolution 3D analyses of the shape and internal constituents of small volcanic ash particles: The contribution of SEM micro-computed tomography (SEM micro-CT)

High-resolution 3D analyses of the shape and internal constituents of small volcanic ash particles: The contribution of SEM micro-computed tomography (SEM micro-CT)

FPLUME-1.0: An integral volcanic plume model accounting for ash aggregation

Modeling ash fall distribution from a Yellowstone supereruption

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