Il progetto EPLORIS: La ricostruzione virtuale dell'eruzione del Vesuvio

The main objective of the Exploris project consists in the quantitative analysis of explosive eruption risk in densely populated EU volcanic regions and the evaluation of the likely effectiveness of possible mitigation measures through the development of volcanic risk facilities (such as supercomputer models, vulnerability databases, and probabilistic risk assessment protocols) and their application to high-risk European volcanoes. Exploris’ main ambition is to make a significant step forward in the assessment of explosive eruption risk in highly populated EU cities and islands. For this project, a new simulation model, based on fundamental transport laws to describe the 4D (3D spatial co-ordinates plus time) multiphase flow dynamics of explosive eruptions has been developed and parallelized in INGV and CINECA. Moreover, CINECA developed specific tools to efficiently visualise the results of simulations. This article presents the results of the large numerical simulations, carred out with CINECA’s Supercomputers, to describe the collapse of the volcanic eruption column and the propagation of pyroclastic density currents, for selected medium scale (sub-Plinian) eruptive scenarios at Vesuvius

An application of parallel computing to the simulation of volcanic eruptions

A parallel code for the simulation of the transient 3D dispersal of volcanic particles produced by explosive eruptions is presented. The model transport equations, based on the multiphase flow theory, describe the atmospheric dynamics of the gas-particle mixture ejected through the volcanic crater. The numerics is based on a finite-volume discretization scheme and a pressure-based iterative non-linear solver suited to compressible multiphase flows. The code has been parallelized by adopting an ad hoc domain partitioning scheme that enforces the load balancing. An optimized communication layer has been built over the Message-Passing Interface. The code proved to be remarkably efficient on several high-performance platforms and makes it possible to simulate fully 3D eruptive scenarios on realistic volcano topography

A Parallel Tree code for large Nbody simulation: dynamic load balance and data distribution on CRAY T3D system

N-body algorithms for long-range unscreened interactions like gravity belong to a class of highly irregular problems whose optimal solution is a challenging task for present-day massively parallel computers. In this paper we describe a strategy for optimal memory and work distribution which we have applied to our parallel implementation of the Barnes & Hut (1986) recursive tree scheme on a Cray T3D using the CRAFT programming environment. We have performed a series of tests to find an " optimal data distribution " in the T3D memory, and to identify a strategy for the " Dynamic Load Balance " in order to obtain good performances when running large simulations (more than 10 million particles). The results of tests show that the step duration depends on two main factors: the data locality and the T3D network contention. Increasing data locality we are able to minimize the step duration if the closest bodies (direct interaction) tend to be located in the same PE local memory (contiguous block subdivison, high granularity), whereas the tree properties have a fine grain distribution. In a very large simulation, due to network contention, an unbalanced load arises. To remedy this we have devised an automatic work redistribution mechanism which provided a good Dynamic Load Balance at the price of an insignificant overhead.Comment: 16 pages with 11 figures included, (Latex, elsart.style). Accepted by Computer Physics Communication

An interactive virtual Environment to comunicate Vesuvius eruptions numerical simulations and Pompeii history

in the filePublishedope