1,721,056 research outputs found
A numerical code for the simulation of transient multicomponent magma dynamics
No full textA numerical code for the simulation of the dynamics of multicomponent fluids based on the highly stable and accurate finite element algorithm by Hauke and Hughes (1998) has been implemented. This numerical method allows a unified approach forcompressible and incompressible transient flows. Therefore, it is particularly suitable for the simulation of the dynamics within magma chambers and along volcanic conduits,
where a wide range of Mach and Reynolds numbers occurs. The balance equations of mass, momentum, energy, and composition are solved for the unknowns pressure, velocity, temperature, and composition of a homogeneous mixture with properties dependent on the local conditions. The equations are discretized in time and space with Galerkin least-squares and discontinuity-capturing stabilizing techniques.
The conservation equations for chemical components have been added to the original Hauke and Hughes (1998) formulation, along with the corresponding stabilization
terms. The linear non-symmetric system of discretized equations is solved with a preconditioned GMRES. The code is written in C++, picking up FE and mathematical
tools from the open source OFELI, Diffpack, and MTL libraries. The computational results have been validated on classical test cases in a wide range of flow conditions from compressible to incompressible. Applications to magma chamber and conduit flow dynamic problems show several features of the multidimensional transient dynamics before, during, and after volcanic eruptions
Numerical investigation of destabilization and overturning in volatile-rich magma chambers
No full textThe effects of volatiles in destabilizing stratified magma chambers are studied with numerical simulations. The system under investigation is a 2D magma chamber hosting a
chemically and thermally stratified magma. Numerical simulations have been carried
out by using a newly developed finite element code for the transient multicomponent dynamics of compressible and incompressible homogeneous flows of volcanological
interest. This code represents an extension of the highly stable and accurate algorithm developed by Hauke and Hughes (1998). The magma properties depend on local conditions in terms of pressure, temperature, and composition, and Newtonian rheology is assumed. Volatiles include water and carbon dioxide in variable proportions and in
chemical equilibrium with the multicomponent liquid. Parametric studies have been carried out on the initial volatiles distribution, magma composition and temperature,
and chamber location, size, and geometry. Computational results allow to define conditions required for the gravitational destabilization of magma within the chamber.
They also show the time-space distribution of chamber pressure, temperature, velocity, and composition, as well as the patterns of convective motions and volatiles exsolution
Simulation of magma mixing in refilled magma chambers driven by gas exsolution
No full textThe dynamics of convection in volatile-rich replenished magma chambers is studied by means of numerical simulations. Simulations are carried out with an appositely developed advanced finite element numerical code, named GALES, which solves the fundamental mass, momentum and energy equations for 2D transient, multicomponent, compressible to incompressible single-fluid flows. The physical properties of magma such as density, viscosity, and volatile saturation depend on local composition, phase distribution, pressure and temperature. The investigated system is an elliptic chamber hosting magma with a certain amount of volatiles, refilled with a volatile-rich magma. Volatiles are water and carbon dioxide. Cases of different amounts of CO2 in the refilling magma, reservoirs located at different depths, magmas with different viscosities, and inlet boundary conditions of either fixed velocities or fixed pressure, are considered. The results show the formation of a gas-rich convective plume along or close to the chamber axis, mixing of resident and refilling magma, and development of large-scale convective cells inside the chamber, with time-scales and efficiencies depending on the specific conditions investigated. Fluid instabilities related to the compressible nature of magma are responsible of the development of pressure transients along the chamber walls, with amplitude of the order of kPa and frequencies in the
range of those pertaining to LP or VLP events registered in volcanic areas
Dataset for: "Last century changes in annual precipitation in a Mediterranean area and their spatial variability. Insights from northern Tuscany (Italy)"
No full textThe version 1.0 contains the supporting data for the work (still under submission) "Last century changes in annual precipitation in a Mediterranean area and their spatial variability. Insights from northern Tuscany (Italy)".
The following files are here available (all file are georeferenced in EPSG: 3003):
- AVG_Rainfall_1990-2019.tif -> Raster map of the mean annual precipitation for the northern Tuscany, Italy. It encompasses the portion of the Tuscany region northern of the cities of Livorno - Florence. The interpolation was validated via a leave one out cross-validation procedure.
- D3-1_Area2_ApuanAlps.tif -> Raster map of the differences in mean annual precipitation between the two 3-decades periods 1921 to 1950 and 1990 to 2019 for the Apuan Alps mountain ridge (Tuscany, Italy).
- D3-2_Area2_ApuanAlps.tif -> Raster map of the differences in mean annual precipitation between the two 3-decades periods 1951 to 1980 and 1990 to 2019 for the Apuan Alps mountain ridge (Tuscany, Italy).
- DeltaSHP_Points_AVG_Annual_Rainfall.zip -> Shape file of the raingauges locations with the mean annual precipitation values of the period 1990 to 2019.
- RaingaugesSHP_Points_AVG_Annual_Rainfall_1990-2019.zip -> Shape file of the raingauges locations with the following information: differences in the mean annual precipitation values between the two 3-decades periods 1951 to 1980 and 1990 to 2019 (named D3-2); p values of the t-test for significance of the differences between the mean annual precipitation ofthe two 3-decades periods 1951 to 1980 and 1990 to 2019; difference in the mean annual precipitation values between the two 3-decades periods 1921 to 1950 and 1990 to 2019 (named D3-1); p values of the t-test for significance of the differences between the mean annual precipitation ofthe two 3-decades periods 1921 to 1950 and 1990 to 2019
Numerical simulation of the eruptive dynamics of volatile-rich magma in magma chambers and volcanic conduits
No full textThe recently developed gales numerical code for the simulation of the dynamics of multicomponent single fluid compressible to incompressible flows is applied to simulate the behaviour of suddenly depressurised volatile-rich magma in magma chambers and volcanic conduits. The physico-chemical properties of magma (density, viscosity, heat capacity, and volatile saturation) depend on local conditions in terms of pressure, temperature, and composition. Parametric studies allow the investigation of the eruption dynamics for several pre-eruptive volatile content and distribution, magma composition and viscosity, and assumed boundary conditions. Numerical results describe the evolution in time and space of magma in the chamber + conduit system, the paths of magma withdrawal, the possible occurrence of magma mixing, and allow to determine mass flow-rates and flow conditions at different times and relevant locations such as volcanic conduit base and exit. Transient dynamics in the opening eruptive phase show processes at the conduit entrance which have never been described before with numerical studies, and which are characterized by pressure oscillations with variable amplitude and 2-4 Hz frequency, as well as significant vorticity in velocity patterns. The computed relationships among magma composition and properties, boundary conditions, and eruptive dynamics are described
Estensione del metodo integrale, considerando l'effetto di eccentricità, per la valutazione delle tensioni residue con i metodi del foro e della cava anulare
No full textSviluppo di un modello per lo studio delle azioni sulle dentature di rotismi epicicloidali impiegati in campo aeronautico
No full textScopo di questo lavoro è lo sviluppo di un modello a parametri concentrati di un riduttore planetario per la stima delle forze agenti sulla dentatura e lo studio delle condizioni in cui si verifica la perdita di contatto e/o l’incuneamento dei denti delle ruote. Diversamente da altri lavori esistenti in letteratura, che analizzano il comportamento dei riduttori in presenza di carichi di coppia ed errori di montaggio, nel seguente lavoro è stata svolta un analisi statica che prende in considerazione il disallineamento delle strutture di supporto dei componenti del riduttore. Il modello sviluppato è stato implementato in un programma in ambiente Matlab (c). Tale programma è in grado di stimare il carico agente su ogni satellite,
anche in presenza di fenomeni di separazione tra i denti. Il software valuta, inoltre, le condizioni di funzionamento per le quali si ha contatto su entrambi i fianchi del dente
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