ASHEE: a multiphase Eulerian-Lagrangian 3D model for volcanic ash plumes and its application to the Calbuco 2015 eruption

| 06 Dicembre 2017 | ore 14.30 | Dott. Matteo Cerminara – INGV Pisa | INGV Sezione di Pisa – Sala Seminari

The three-dimensional ASHEE (ASH Equilibrium Eulerian) model simulates compressible multiphase-multicomponent turbulent flows up to a scale of the order of 100 km. Ash particles finer than 1 mm are included within the Eulerian approach, while coarser particles are treated with a Lagrangian approach. Kinematic disequilibrium, including particle settling and clustering, is taken into account for all the particle classes.
Realistic atmospheric profiles can be used, including moisture and wind.
Turbulence is modeled using the dynamic Large Eddy Simulation approach, to capture accurately and efficiently the energy spectrum of the flow without using any empirical parameter.
A number of fluid dynamics benchmarks has been used to measure the accuracy of ASHEE, in a wide range of physical conditions.
ASHEE is a parallel code, written using the OpenFOAM C++ libraries. It can be used on High Performance Computing infrastructures, up to 6000 cores, with more than 70 % of efficiency.
Eruption source parameters (ESP) of the April 2015 Calbuco explosive eruption have been selected from recent literature measurements and estimations, both from remote observations and analysis of the deposit. The mass eruption rate and the lapilli grain size distribution have been varied to reproduce observations: maximum plume height, umbrella cloud expansion and height, and proximal deposit thickness. The best fitting result gives information on the ESP of the first phase of the eruption (22 April, 18:00 – 19:30 UTC).
Finally, three-dimensional data have been filtered to provide the necessary input parameters to ash dispersion models.

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