Experimental investigation of the aggregation‐disaggregation of colliding volcanic ash particles in turbulent, low‐humidity suspensions

Bello, E. Del; Taddeucci, Jacopo; Scarlato, Piergiorgio; Giacalone, Emanuele; Cesaroni, Claudio

doi:10.1002/2014gl062292

Cited by 16 publications

(17 citation statements)

References 37 publications

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“…These peculiarities must be accounted for in future modelling and in hazard forecast preparedness concerning ash resuspension events. Further experimental studies are planned to investigate: i) micro-scale detachment dynamics, also in relation with the formation/disruption of ash aggregates 41 ; and ii) changes in U th * as a function of the residence time and complex grain size distributions of ash layers.…”

Section: Discussionmentioning

confidence: 99%

Experimental simulations of volcanic ash resuspension by wind under the effects of atmospheric humidity

Bello

Taddeucci

Merrison

et al. 2018

Sci Rep

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Ash deposited during volcanic eruptions can be resuspended by wind and become hazardous for health and infrastructure hours to decades after an eruption. Accurate resuspension forecasting requires accurate modelling of the threshold friction velocity of the volcanic particles (Uth*), which is the key parameter controlling volcanic ash detachment by wind. Using an environmental wind tunnel facility this study provides much needed experimental data on volcanic particle resuspension, with the first systematic parameterization of Uth* for ash from the regions Campi Flegrei in Italy and also Eyjafjallajökull in Iceland. In this study atmospheric relative humidity (and related ash moisture content) was systematically varied, from <10% to >90%, which in the case of the Eyjafjallajökull fine ash (<63 μm) produced a twofold increase in Uth*. Using the Campi Flegrei fine ash (<63 μm) an increase in Uth* of only around a factor of 1.5 was observed. Reasonable agreement with force balance resuspension models was seen, which implied an increase in interparticle adhesion force of up to a factor of six due to high humidity. Our results imply that, contrary to dry conditions, one single modelling scheme may not satisfy the resuspension of volcanic ash from different eruptions under wet conditions.

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Section: Discussionmentioning

confidence: 99%

Experimental simulations of volcanic ash resuspension by wind under the effects of atmospheric humidity

Bello

Taddeucci

Merrison

et al. 2018

Sci Rep

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“…Such an increase in particle settling rate would result in earlier deposition of particles of a given size (and consequent depletion of such particles from the plume), affecting the areal and grain size distributions of eruption deposits. Inside such regions, four-way coupling will also impact particle aggregation and disaggregation processes43, and possibly remove finer particles from the plume because of their sweeping by the downdraft of larger ones. Our observations may be also extended to the study of pyroclastic density currents, where the settling velocity of particles is often used to infer the physical properties of the flow44.…”

Section: Discussionmentioning

confidence: 99%

Effect of particle volume fraction on the settling velocity of volcanic ash particles: insights from joint experimental and numerical simulations

Bello

Taddeucci

Vitturi

et al. 2017

Sci Rep

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Most of the current ash transport and dispersion models neglect particle-fluid (two-way) and particle-fluid plus particle-particle (four-way) reciprocal interactions during particle fallout from volcanic plumes. These interactions, a function of particle concentration in the plume, could play an important role, explaining, for example, discrepancies between observed and modelled ash deposits. Aiming at a more accurate prediction of volcanic ash dispersal and sedimentation, the settling of ash particles at particle volume fractions (ϕp) ranging 10−7-10−3 was performed in laboratory experiments and reproduced by numerical simulations that take into account first the two-way and then the four-way coupling. Results show that the velocity of particles settling together can exceed the velocity of particles settling individually by up to 4 times for ϕp ~ 10−3. Comparisons between experimental and simulation results reveal that, during the sedimentation process, the settling velocity is largely enhanced by particle-fluid interactions but partly hindered by particle-particle interactions with increasing ϕp. Combining the experimental and numerical results, we provide an empirical model allowing correction of the settling velocity of particles of any size, density, and shape, as a function of ϕp. These corrections will impact volcanic plume modelling results as well as remote sensing retrieval techniques for plume parameters.

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“…The results of both experiments were used to study capillary binding forces in moist particles and grain size selection and deposition due to electrostatic forces. Recently Van Eaton et al [2012], Del Bello et al [2015], Mueller et al [2016] and Mueller et al,[2017; have further extended the knowledge on the mechanisms of aggregation by water bounds between particles. Van Eaton et al…”

Section: Introductionmentioning

confidence: 99%

“…[2012] used a vibratory pan to show the first trials of ice aggregation below freezing at room temperature and the influence of water content (liquid and ice) on aggregation coefficient. Del Bello et al [2015] present the first attempt to parameterize the joint roles of aggregation and disaggregation on the behavior of volcanic ash particles transported within gaseous suspension. Mueller et al [2016] and successfully produced aggregates in laboratory using fluidization techniques, but only when particles were coated with volumetrically relevant NaCl (~2000 mg Kg -1 ) well-structured aggregates were recovered.…”

Section: Introductionmentioning

confidence: 99%

Volcanic ash aggregation enhanced by seawater interaction: the case of Secche di Lazzaro phreatomagmatic deposit (Stromboli)

Morgavi

Valentini²,

Porreca³

et al. 2019

Annals of Geophysics

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The Secche di Lazzaro formation (ca. 6.2-7 kys BP) is a phreatomagmatic deposit situated in the southwestern part of the island of Stromboli (Aeolian Archipelago, Italy). The volcanic sequence is comprised of three main units. In the lower unit accretionary lapilli are particularly abundant and are characterized by strong cementation between the particles and an uncommon resistance to breakage. To understand the processes behind the formation of the Secche di Lazzaro (SdL) accretionary lapilli a multi-analytical approach was used on the lapilli Aggregate Tuff (AT), and on single Accretionary Lapilli (AL). We carried out granulometric analysis, Field Emission-Scanning Electron Microscopy (FE-SEM), Electron Microprobe Analysis (EMPA), X-ray powder diffraction (XRPD) and 3D imaging by X-ray micro-tomography (X-mCT). The granulometric data show that most particles in the AT have a diameter equal to Φ-1 corresponding to 2 mm. The EMPA, FE-SEM and XRPD analyses reveal the presence of different mineral phases, mainly plagioclase, K-feldspar, halite, and clinopyroxene, together with volcanic glass. From the X-mCT analysis, we constrained the particle distribution and estimated the porosity of AL. The results of the FE-SEM images provided the chemical distribution within individual lapilli allowing the identification of rim and core zoning as well as the presence of halite located both on the border of single lapilli and on the juncture between different lapilli. Moreover, halite occurs among different aggregates in single AL, thus acting as a binding agent, as well as within rim pores. The results of this work shed new light into the formation of accretionary lapilli in phreatomagmatic eruption a t volcanic island involving marine water.

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Experimental investigation of the aggregation‐disaggregation of colliding volcanic ash particles in turbulent, low‐humidity suspensions

Cited by 16 publications

References 37 publications

Experimental simulations of volcanic ash resuspension by wind under the effects of atmospheric humidity

Experimental simulations of volcanic ash resuspension by wind under the effects of atmospheric humidity

Effect of particle volume fraction on the settling velocity of volcanic ash particles: insights from joint experimental and numerical simulations

Volcanic ash aggregation enhanced by seawater interaction: the case of Secche di Lazzaro phreatomagmatic deposit (Stromboli)

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