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Numerical, experimental and field investigations of particle aggregation

English title Numerical, experimental and field investigations of particle aggregation
Applicant Bonadonna Costanza
Number 125024
Funding scheme Project funding
Research institution Département des sciences de la Terre Université de Genève
Institution of higher education University of Geneva - GE
Main discipline Mineralogy
Start/End 01.08.2009 - 30.09.2012
Approved amount 336'900.00
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All Disciplines (2)

Discipline
Mineralogy
Other disciplines of Earth Sciences

Keywords (13)

particle aggregation; Cellular Automata; Lattice Boltzmann; modelling; tephra; laboratory experiments; particle sedimentation; explosive volcanism; volcanic ash; numerical modeling; wind tunnel; Mount St Helens; Montserrat

Lay Summary (English)

Lead
Lay summary
Processes of particle aggregation play a fundamental role in the sedimentation of tephra from volcanic plumes and, in particular, in the sedimentation of the fine-ash fraction (<63 microns). In fact, field observations and laboratory experiments have shown that particles with diameter <100 microns do not fall individually but they aggregate in clusters of different types. Most explosive eruptions produce fine ash as a result of magma fragmentation. The characterization and the hazard assessment of eruptions producing a large amount of fine ash require a thorough understanding and parameterization of particle aggregation. Unfortunately, even though both analytical and numerical models typically used to describe tephra transport and sedimentation have now reached a high level of sophistication, they still do not account for particle aggregation and, therefore, they fail to describe sedimentation of fine ash. This has important implications on the associated long-term hazard assessments of tephra sedimentation, real-time forecast of ash-rich plumes and health-hazard assessments. Recent experimental investigations have resulted in empirical parameterizations of particle aggregation in both wet and dry environment, but, given the empirical nature of these results, they cannot be generalized to provide a comprehensive aggregation model. Numerical studies have also provided important insights, but, due to the complex nature of these highly sophisticated models, they still require validation with field observations and they cannot be easily applied to hazard assessments of any form. We propose to combine theoretical, numerical, experimental and field investigations of particle aggregation in order to provide a comprehensive, accurate and reliable numerical model for tephra sedimentation from volcanic plumes. In particular, we are planning to run laboratory experiments for particle collision and for both dry and wet aggregation using a wind tunnel for the study of particle settling. The new model for particle transport, aggregation and sedimentation will be tested using laboratory experiments and two field datasets: the new dataset of particle grainsize and aggregation characterization associated with the 1980 eruption of Mt St Helens and the new dataset that will be collected in Montserrat (WI) within this project. In particular, we are planning to carry out field observations of particle aggregation during the current eruption of Soufrière Hills Volcano, Montserrat (WI), characterized by ash-rich fallout. We will measure settling velocity of particle clusters in situ and we will collect individual clusters for dedicated analysis in the lab.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
Improving on mass flow rate estimates of volcanic eruptions
Degruyter Wim and Bonadonna Costanza (2012), Improving on mass flow rate estimates of volcanic eruptions, in GEOPHYSICAL RESEARCH LETTERS, 39, L16308-L16308.
Comparison of Two Advection-Diffusion Methods for Tephra Transport in Volcanic Eruptions
Tsunematsu Kae Chopard Bastien Falcone Jean-Luc and Bonadonna Costanza (2011), Comparison of Two Advection-Diffusion Methods for Tephra Transport in Volcanic Eruptions, in Communications in Computational Physics, 9(5), 1323-1334.
A Review of Volcanic Ash Aggregation
Brown Richard Bonadonna Costanza Durant Adam, A Review of Volcanic Ash Aggregation, in Chemistry and Physics of the Earth, xx, 111-222.
Ash-Plume Dynamics and Eruption Source Parameters by Infrasound: the 2010 Eyjafjallajökull Eruption
Ripepe M. Bonadonna C. Folch A. Delle Donne D. Lacanna G. Höskuldsson A., Ash-Plume Dynamics and Eruption Source Parameters by Infrasound: the 2010 Eyjafjallajökull Eruption, in Earth and Planetary Science Letters.
Scavenging of sulphur, halogens and trace metals by volcanic ash: the 2010 Eyjafjallajökull eruption
Bagnato E. Aiuppa A. Bertagnini A. Bonadonna C. Cioni R. Pistolesi M. Pedone M. Hoskuldsson A, Scavenging of sulphur, halogens and trace metals by volcanic ash: the 2010 Eyjafjallajökull eruption, in Geochimica et Cosmochimica Acta.
Tephra sedimentation during the 2010 Eyjafjallajökull eruption (Iceland) from deposit, radar and satellite observations
Bonadonna Costanza, Tephra sedimentation during the 2010 Eyjafjallajökull eruption (Iceland) from deposit, radar and satellite observations, in Journal of Geophysical Research, xx, 111-222.

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved


Associated projects

Number Title Start Funding scheme
116335 Characterization of the dynamics and the products of basaltic explosive volcanism 01.07.2007 Project funding
144974 Acquisition of QEMSCAN Automated High-Resolution Mineral and Petrographic Analysis. 01.12.2012 R'EQUIP
169463 Modelling settling-driven gravitational instabilities from volcanic clouds 01.09.2017 Project funding
137942 Combining geophysical observations and numerical modelling for an improved prediction of volcanic ash dispersal 01.02.2012 Project funding
144470 Experimental and field investigations of particle aggregation 01.11.2012 Project funding
144470 Experimental and field investigations of particle aggregation 01.11.2012 Project funding

Abstract

This project is the continuation of the currently FNS funded project No: 200021-116335, which is supporting the first two years of the PhD of Ms K. Tsunematsu at the Department of Mineralogy, University of Geneva (August 2007 to July 2009). The PhD of Ms Kae Tsunematsu is focused on the Cellular-Automata-Lattice-Boltzmann (CA-LB) numerical modeling of particle transport, aggregation and deposition. With this new three-year proposal we plan to fund the remaining two years of Ms K. Tsunematsu’s PhD, together with a new PhD project focused on the field and experimental investigations of particle aggregation crucial to the validation of the CA-LB model and to the formulation of a comprehensive model for particle aggregation.Processes of particle aggregation play a fundamental role in the sedimentation of tephra from volcanic plumes and, in particular, in the sedimentation of the fine-ash fraction (<63 microns). In fact, field observations and laboratory experiments have shown that particles with diameter <100 microns do not fall individually but they aggregate in clusters of different types, mainly depending on particle and atmospheric properties. Clusters include: dry aggregates, coated crystals and accretionary lapilli. Most explosive eruptions produce fine ash as a result of magma fragmentation, but such a size fraction is particularly characteristic of fallout from pyroclastic density currents, Vulcanian eruptions and eruptions controlled by magma-water interaction (e.g. phreato-magmatic activity). The characterization and the hazard assessment of eruptions producing a large amount of fine ash require a thorough understanding and parameterization of particle aggregation. Unfortunately, even though both analytical and numerical models typically used to describe tephra transport and sedimentation have now reached a high level of sophistication, they still do not account for particle aggregation and, therefore, they fail to describe sedimentation of fine ash. This has important implications on the associated long-term hazard assessments of tephra sedimentation, real-time forecast of ash-rich plumes and health-hazard assessments.Recent experimental investigations have resulted in empirical parameterizations of particle aggregation in both wet and dry environment, but, given the empirical nature of these results, they cannot be generalized to provide a comprehensive aggregation model. Numerical studies have also provided important insights (mainly on wet aggregation), but, due to the complex nature of these highly sophisticated models, they still require validation with field observations and they cannot be easily applied to hazard assessments of any form. We propose to combine theoretical, numerical, experimental and field investigations of particle aggregation in order to provide a comprehensive, accurate and reliable model for tephra sedimentation from volcanic plumes. In particular, during the current project funded by the Fonds National Suisse (No: 200021-116335), we have implemented and tested a Cellular-Automata-Lattice-Boltzmann model for the description of tephra transport and sedimentation. Validation with field data confirmed that any model of tephra sedimentation fails to reproduce tephra deposits characterized by fine ash if particle aggregation is not accurately described. In addition, we have started developing a theoretical approach to particle aggregation based on the Smoluchowski theory. We intend to implement the existing CA-LB model for tephra transport using this theoretical approach for particle aggregation and validate it with experimental and field observations. In particular, we are planning to run experiments for particle collision and for both dry and wet aggregation using a wind tunnel designed during the current FNS project in collaboration with the Ecole d'ingénieurs de Genève (CMEFE - Groupe de compétences en mécanique des fluides et procédés énergétiques / IMEC) for the study of particle settling. We are particularly interested in investigating aggregation processes over time in order to understand what controls the growth rate of particle clusters. We are also planning to investigate collision and sticking efficiency separately and to study the relative effect of differential settling velocity and turbulence on particle collision. Finally, we want to make a direct link between numerical and experimental investigations.The new CA-LB model for particle transport, aggregation and sedimentation will be tested using laboratory experiments and two field datasets: the new dataset of particle grainsize and aggregation characterization associated with the 1980 eruption of Mt St Helens (provided by Dr. A Durant) and the new dataset that will be collected in Montserrat (WI) within this project. In particular, we are planning to carry out field observations of particle aggregation during the current eruption of Soufrière Hills Volcano, Montserrat (WI), characterized by ash-rich fallout. We will measure settling velocity of particle clusters in situ and we will collect individual clusters for analysis in the lab (i.e. grainsize, porosity, componentry, particle properties, SEM analyses).The project team is particularly well-qualified because it includes experts in the field of computer modeling and CA-LB solutions (Prof. B Chopard and Dr. JL Falcone), experts in the study of tephra deposits (Prof. C Bonadonna), experts in fluid dynamics (Dr. JC Phillips, Prof. Noca and Prof. P Haas), experts in the field of aggregation (Dr A Durant and Dr M James), and experts in the study of particle settling (Dr. S Scollo). The two PhD candidates have also already produced significant contributions in the field of CA modeling (Ms K Tsunematsu) and plume dynamics (Ms H Yamamoto). We are planning to publish our results in high-impact factor journals, to present our work to the international scientific community, to integrate all the numerical models within the multiscale simulation environment currently developed by Prof. Chopard and Dr. Falcone in the European project COAST, and to make our final CA-LB model open-source and available online for other modelers to use and apply within their own work.
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