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New model for aggregation of ash in explosive volcanic eruptions

Georgios Efstathiou 1, George Papadakis2, William P. Jones1, Ben Devenish3, Stelios Rigopoulos1

  • Affiliations: 1 Department of Mechanical Engineering, Imperial College London, London, UK, 2 Department of Aeronautics, Imperial College London, London, UK, 3 Met Office, Exeter, UK 

  • Presentation type: Poster

  • Presentation time: Thursday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 82

  • Programme No: 3.12.8

  • Theme 3 > Session 12

Abstract

In this work we propose a new three dimensional model for the modelling of ash aggregation in Plinian-phreatomagmatic volcanic eruptions. The model comprises the coupling of the compressible Navier-Stokes equations with the population balance equation in the large eddy simulations framework. Similarly to a previously proposed multiphase model for volcanic eruption columns, an equilibrium-Eulerian approach is used to represent the transport of particles which are assumed to be low inertia and two-way coupled with the flow. For the aggregation process we deploy our recently developed methodology which is tailored to explicitly calculate the size distribution and conserve the mass of particles by identifying the source bins of the particles which compose every newly developed aggregate. We firstly validate our approach against other computational models based on the results presented in a inter-model comparison study and secondly, we display the effect of aggregation in the eruption column and the final size distribution of particles which survive into the far field by using 20 size classes of ash particles. The results set the baseline for obtaining valuable insights regarding the interaction between turbulence and ash aggregation. This is an essential step towards the calibration of real time one-dimensional plume models which are used for the initialisation of dispersion models.