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Authors: Esposti Ongaro, T.*
Barsotti, S.*
Neri, A.*
Salvetti, M. V.*
Editors: Salvetti, M. V.; Aerospace Engineering Department, University of Pisa, Pisa, Italy
Geurts, B.; Multiscale Modeling and Simulation, Faculty EEMCS, University of Twente, Enschede, The Netherlands; Anisotropic Turbulence, Faculty Applied Physics, Eindhoven University of Technology, Eindhoven, The Netherlands
Meyers, J.; Katholieke Universiteit Leuven, Div. Appl. Mechanics & Energy Conversion, Leuven, Belgium
Sagaut, P.; Université Pierre et Marie Curie 6, Institut Jean le Rond d'Alembert, Paris Cedex, France
Title: Large-eddy simulation of pyroclastic density currents
Issue Date: 2010
ISBN: 978-94-007-02.30-1
Keywords: Large-Eddy Simulation
pyroclastic density currents
numerical simulation
multiphase flows
Abstract: We investigate the dynamics of turbulent pyroclastic density currents (PDCs) by adopting a 3D, Eulerian-Eulerian multiphase flow model, in which solid particles are treated as a continuum and the grain-size distribution is simplified by assuming two particulate phases. The turbulent sub-grid stress of the gas phase is modelled within the framework of Large-Eddy Simulation (LES) by means of a eddy-viscosity model together with a wall closure. Despite the significant numerical diffusion associated to the upwind method adopted for the Finite-Volume discretization, numerical simulations demonstrate the need of adopting a Sub-Grid Scale (SGS) model, while revealing the complex interplay between the grid and the SGS filter sizes. We also analyse the relationship between the averaged flow dynamic pressure and the action exerted by the PDC on a cubic obstacle, to evaluate the impact of a PDC on a building. Numerical results suggest that the average flow dynamic pressure can be used as a proxy for the force per unit surface acting on the building envelope (Fig. 5), even for such steeply stratified flows. However, it is not possible to express such proportionality as a constant coefficient such as the drag coefficient in a steady-state current. The present results indeed indicate that the large epistemic and aleatory uncertainty on initial and boundary conditions has an impact on the numerical predictions which is comparable to that of grid resolution.
Appears in Collections:04.08.99. General or miscellaneous
Book chapters
05.01.99. General or miscellaneous

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