http://hdl.handle.net/2122/271 Ricerca nel canale cerca http://www.earth-prints.org/simple-search http://hdl.handle.net/2122/5833 Titolo: Large-eddy simulation of pyroclastic density currents<br/><br/>Autori: Esposti Ongaro, T.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Barsotti, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Neri, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Salvetti, M. V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia<br/><br/>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 roportionality 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 redictions which is comparable to that of grid resolution. http://hdl.handle.net/2122/5830 Titolo: Wavelet decomposition and advanced denoising techniquesn for analysis and classification of seismic signals<br/><br/>Autori: Galli, L.; Advanced Computer Systems, Rome, Italy; Castellani, C.; Advanced Computer Systems, Rome, Italy; Pace, G.; Advanced Computer Systems, Rome, Italy; Saccorotti, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia<br/><br/>Curatori: Bean, C. J.; chool of Geological Sciences, University College Dublin, Ireland; Braiden, A. K.; School of Geological Sciences, University College Dublin, Ireland; Lokmer, I.; School of Geological Sciences, University College Dublin, Ireland; Martini, F.; School of Geological Sciences, University College Dublin, Ireland; O’Brien, G. S.; School of Geological Sciences, University College Dublin, Ireland<br/><br/>Abstract: This work describes an automatic classification procedure for seismic signalssuitable for the analysis of complex, broad-band waveforms commonlyassociated with fluid-rock interaction in volcanic and hydrothermal systems.Based on Discrete Wavelet Transform, a set of significant seismic signalfeatures that characterize the type of event is identified (e.g. noise, volcanotectonic, long period). These features are initially assessed for events whosecategory (class) can be previously determined by an expert analyst. A BayesianPattern Recognition supervised technique based on these features is adoptedto classify a new ‘unlabelled pattern’, whose class is unknown. In this wayvalues computed for known events are used to classify events of unknownidentity ('supervised classification'). A test was performed on seismological datarecorded at Campi Flegrei (Italy), which was divided into three classes.Automatic classification accuracy ranges from 82% to 100% over a broad rangeof datasets. http://hdl.handle.net/2122/5720 Titolo: FITOVERT: A dynamic numerical model of subsurface vertical flow constructed wetlands<br/><br/>Autori: Giraldi, D.; Department of Civil Engineering, University of Pisa, Pisa, Italy; De' Michieli Vitturi, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Iannelli, R.; Department of Civil Engineering, University of Pisa, Pisa, Italy<br/><br/>Abstract: This paper introduces a mathematical model (FITOVERT) specifically developed to simulate the behaviour of vertical subsurface flow constructed wetlands (VSSF-CWs). One of the main goals of the development of FITOVERT was to keep the complexity of the model to an acceptable level, so as to provide a practical tool for design and operation optimization. The dynamic formulation of the model allows to simulate the typical non stationary feeding-emptying operation of VSSF-CWs. FITOVERT is able to describe the water flow through porous media in unsaturated conditions, combined with evapotranspiration; its biochemical module describes the degradation of both organic matter and nitrogen; the transport in the liquid phase is implemented for both dissolved and particulate components; the oxygen transport in the gaseous phase of the soil and its exchange with the liquid phase are also considered. As a main advantage, compared to the few currently available dedicated numerical models, FITOVERT is able to handle the porosity reduction due to bacteria growth and accumulation of particulate components, so that the clogging process is also simulated as an effect of the pore size reduction on the hydraulic conductivity of the simulated system. The performance of the model was firstly analyzed by comparison with hydrodynamic tests recorded in an experimental VSSF-CW pilot plant: tracer test were carried out in three different saturation conditions (fully saturated, partially saturated, and completely drained). FITOVERT proved to accurately simulate the hydraulic behaviour of VSSF-CWs in both saturated and unsaturated conditions. The needs for model improvements and further calibration are finally discussed. http://hdl.handle.net/2122/5714 Titolo: Hydrodynamics of vertical subsurface flow constructed wetlands: Tracer tests with rhodamine WT and numerical modelling<br/><br/>Autori: Giraldi, D.; Department of Civil Engineering – University of Pisa, Pisa, Italy; De' Michieli Vitturi, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Zaramella, M.; Department of Hydraulic, Maritime, Environmental and Geotechnical Engineering – University of Padua, Padova, Italy; Marion, A.; Department of Hydraulic, Maritime, Environmental and Geotechnical Engineering – University of Padua, Padova, Italy; Iannelli, R.; Department of Civil Engineering – University of Pisa, Pisa, Italy<br/><br/>Abstract: Typical unsteady unsaturated conditions can profoundly affect the hydrodynamics of vertical subsurface flow constructed wetlands. In this study we analyzed the hydrodynamics of a 33 m2 vertical flow pilot plant, treating municipal secondary effluents. Three different saturation conditions were analyzed under several constant flux regimes: complete saturation, partial saturation with the free water table 20 cm over the bottom of the bed, and complete drainage. Tracer tests were performed in steady state conditions by dosing rhodamine WT as square input signals. Breakthrough curves were analyzed by means of both a classical residence time distribution analysis and an originally developed numerical plug-flow model with longitudinal dispersion adapted to the unsaturated conditions. We found that the degree of global mixing in the vertical flow constructed wetland increased as the water content increased; this effect was controlled by the hydraulic residence time of the system. Conversely, the degree of local mixing was inversely affected by water content; the dispersivity was 4.5, 10, and 14 cm for fully saturated, partially saturated and draining conditions, respectively. We explain the dependency of dispersivity on water content in physical terms; however, further studies are needed to mathematically include this relationship in numerical models that describe the behaviour of vertical flow constructed wetlands. http://hdl.handle.net/2122/5515 Titolo: Application of the Post-Widder Laplace inversion algorithm to postseismic rebound models<br/><br/>Autori: Cannelli, Valentina; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Melini, Daniele; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Piersanti, Antonio; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Spada, Giorgio; Istituto di Fisica, Università di Urbino "Carlo Bo" - Urbino, Italy<br/><br/>Abstract: The postseismic response of a viscoelastic Earth can be computedanalytically with a normal-mode approach, based on the application of propagatormethods. This framework suffers from many limitations, mostly connected with thesolution of the secular equation, whose degree scales with the number of viscoelasticlayers so that only low-resolution models can be practically solved. Recently, aviable alternative to the normal-mode approach has been proposed, based on thePost-Widder inversion formula. This method allows to overcome some of the intrinsiclimitations of the normal-mode approach, so that Earth models with arbitraryradial resolution can be employed and general linear non-Maxwell rheologies can beimplemented. In this work, we test the robustness of the method against a standardnormal-mode approach in order to optimize computation performance whileensuring the solution stability. As an application, we address the issue of findingthe minimum number of layers with distinct elastic properties needed to accuratelydescribe the postseismic relaxation of a realistic Earth model. http://hdl.handle.net/2122/5501 Titolo: Predicting the impact of lava flows at Mount Etna (Italy)<br/><br/>Autori: Crisci, G.; Department of Earth Sciences, University of Calabria, 87036 Rende, Italy; Avolio, M. V.; Department of Mathematics, University of Calabria, 87036 Rende, Italy; Behncke, B.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; D'Ambrosio, D.; Department of Mathematics, University of Calabria, 87036 Rende, Italy; Di Gregorio, S.; Department of Mathematics, University of Calabria, 87036 Rende, Italy; Lupiano, V.; Department of Earth Sciences, University of Calabria, 87036 Rende, Italy; Neri, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Rongo, R.; Department of Earth Sciences, University of Calabria, 87036 Rende, Italy; Spataro, W.; High Performance Computing Centre, University of Calabria, 87036 Rende, Italy<br/><br/>Abstract: Forecasting the time, nature and impact of future eruptions is difficult at volcanoes such as Mount Etna, in Italy, where eruptions occur from the summit and on the flanks, affecting areas distant from each other. Nonetheless, the identification and quantification of areas at risk from new eruptions is fundamental for mitigating potential human casualties and material damage. Here, we present new results from the application of a methodology to define flexible high-resolution lava invasion susceptibility maps based on a reliable computational model for simulating lava flows at Etna and on a validation procedure for assessing the correctness of susceptibility mapping in the study area. Furthermore, specific scenarios can be extracted at any time from the simulation database, for land-use and civil defence planning in the long-term, to quantify, in real-time, the impact of an imminent eruption, and to assess the efficiency of protective measures. http://hdl.handle.net/2122/5379 Titolo: FALL3D: A computational model for transport and deposition of volcanic ash<br/><br/>Autori: Folch, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Costa, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Macedonio, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia<br/><br/>Abstract: FALL3D is a3-Dtime-dependent Eulerian model for the transport and deposition ofvolcanic ashesandlapilli.Themodelsolvestheadvection–diffusion–sedimentation(ADS)equationonastructuredterrain-followinggridusingasecond-orderfinitedifferences(FD)explicitscheme.Differentparameterizationsfortheeddydiffusivitytensor andfortheparticleterminalsettlingvelocitiescanbeused.Thecode,writteninFORTRAN90, isavailableinbothserialandparallelversionsforWindowsandUnix/Linux/MacXoperatingsystems(OS).Aseriesofpre-andpost-processutilityprograms andOS-dependentscriptstolaunchthemarealsoincludedinthe FALL3Ddistributionpackage.Althoughthemodelhasbeendesignedtoforecastvolcanicashconcentrationintheatmosphereandashloadingatground,itcanalsobeusedtomodelthetransportofanykindofairbornesolidparticles.Themodelinputsaremeteorologicaldata,topography,grain-sizedistribution,shapeanddensityofparticles,and massrateofparticleinjectedintotheatmosphere.Optionally, FALL3D can becoupledwiththeoutputofthemeteorologicalprocessor CALMET, adiagnosticmodelwhichgenerates3-Dtime-dependentzero-divergencewindfieldsfrommesoscaleforecastsincorporatinglocalterraineffects.The FALL3D model canbeatoolforshort-termashdepositionforecastingandforvolcanicfallouthazardassessment.Asanexample,anapplicationtothe22July1998Etnaeruptionisalsopresented http://hdl.handle.net/2122/4948 Titolo: The Fermi function performance in geomagnetic data inversion<br/><br/>Autori: Faggioni, O.; Istituto Geofisica Marina - CUNISPE; Beverini, N.; UNIPI; Caratori Tontini, F.; Istituto Geofisica Marina - CUNISPE; Carmisciano, C.; Istituto Geofisica Marina - CUNISPE<br/><br/>Abstract: We present a method for inversion of geomagnetic data for 3D source's magnetization modeling based on a generalization of the well known Fermi Distribution Function..... http://hdl.handle.net/2122/4945 Titolo: Depth-to-the-bottom optimization for potential field inversion<br/><br/>Autori: Caratori Tontini, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Cocchi, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Carmisciano, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia<br/><br/>Abstract: We present an algorithm for the linear inversion of 2D surface magnetic data to obtain 3D models of the susceptibility of the source. The forward model is discretized by a mesh of prismatic cells with constant magnetization that allows the recovery of a complete 3D generating source..... http://hdl.handle.net/2122/4793 Titolo: STUDY OF THE GROWTH RATE IN DECOMPRESSION-INDUCED CRYSTALLIZATION EXPERIMENTS of alkali feldspars in trachytic melts of Phlegrean Fields (Napoli, Italy)<br/><br/>Autori: Calzolaio, M.; Department of Earth Sciences - University of Camerino; Arzilli, F.; DepartmentDepartment of Earth Sciences - University of Camerino; Carroll, M. R.; Department of Earth Sciences- University of Camerino; Piochi, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia<br/><br/>Abstract: no abstracts