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Geophysics with parallel spectral elements
No full textSpectral Elements have been applied to various applications in computational engineering, and
enable reductions of computational resources respect to more traditional techniques like finite
elements or finite differences. The main advantage is their high order approach, which equals the
accuracy of low order methods while showing computational efficiency and suitability to parallel
computation. This work illustrates how Spectral Elements can be used to solve various problems
usually encountered in geophysics, such as the scalar acoustic equation and linear and non-linear
elasticity
Agricultural impacts on groundwater: Processes, modelling, and decision support
Get PDFThis contribution deals in general with the assessment of agricultural production processes in relation to the environment, with specific emphasis given to groundwater resources in southern European countries and the Mediterranean. We will describe these production processes, their relation to and impact on groundwater, and the basic mechanisms and dynamics involved in the flow of water and transport of contaminants in soil and aquifer systems. An example of different modelling approaches is given, and the limitations and advantages of various approaches are discussed
Modeling and Analysis of Seawater Intrusion in the Coastal Aquifer of Eastern Cap-Bon, Tunisia
Get PDFA numerical model that treats density-dependent variably saturated flow and miscible salt transport is used to investigate the occurrence of seawater intrusion in the ‘Korba’ aquifer of the eastern coast of Cap-Bon in northern Tunisia. We examine the interplay between pumping regimes and recharge scenarios and its effect on the saline water distribution. More localized simulations are used to examine, in vertical cross sections, the effects of well location and soil type and the role of the vadose zone in possible remediation actions. The exploratory simulations suggest interesting interactions between the unsaturated zone and the saltwater–freshwater interface with possible implications for groundwater exploitation from shallow unconfined coastal aquifers, involving in one case feedback between seawater intrusion and the high pressure head gradients around the pumping-induced drawdown cone and in another case threshold-like interface displacement for tight soils such as clays. The data processing steps undertaken in this GIS and modeling study are described in some detail, and a critical assessment is given of the data availability and of the requirements for successful monitoring and modeling of seawater intrusion risks in heavily exploited coastal aquifers such as those found in the semi-arid regions of the Mediterranean basin. It is shown how, with the aid of GIS, reasonably reliable information can be assembled from maps, surveys, and other sources of geospatial and hydrogeological data, an approach that is necessary in the many regions of the world with acute water resource problems but with limited means for undertaking systematic data acquisition and environmental monitoring actions. Nonetheless the need for more concerted monitoring of relevant parameters and processes and of closer coordination between monitoring and modeling is stressed. An idea of the extent of over-exploitation of the Korba aquifer is obtained by examining the pumping and rainfall/infiltration data, and the simulation results support groundwater pumping as the mechanism for and seawater intrusion as the origin of the salt contamination observed in the soils and subsurface waters of the Korba plain.3-28Pubblicat
Development of the TFC turbulent premixed combustion model: the combustion rates and the counter-gradient transport phenomenon
Get PDFWe analyze to “bottlenecks” of turbulent premixed combustion modeling at developed turbulence corresponding to modern lean-premixed large-scale industrial gas-turbine combusters when instantaneous combustion (heat release) takes place in thin strongly wrinkled surface (flamelet sheets)
Implementazione del codice Ares su architetture parallele
No full textThis report describes the MPI parallelization of the combustion code Ares. First, the structure of the code is described, then a detailed analysis of the algorithms used to integrated the flow equation is carried out, with particular emphasis to the parallelization issues. An analysis of few possible alternative approaches is then followed by the description of the chosen approach. A preliminary validation of the parallel code completes the report. Thorough validation on 3D complex test cases will be presented in the next report
Developing a virtual reality environment for petrous bone surgery: a state-of-the-art review
Get PDFThe increasing power of computers has led to the development of sophisticated systems that aim to immerse the user in a virtual environment. The benefits of this type of approach to the training of physicians and surgeons are immediately apparent. Unfortunately the implementation of “virtual reality” (VR) surgical simulators has been restricted by both cost and technical limitations. The few successful systems use standardized scenarios, often derived from typical clinical data, to allow the rehearsal of procedures. In reality we would choose a system that allows us not only to practice typical cases but also to enter our own patient data and use it to define the virtual environment. In effect we want to re-write the scenario every time we use the
environment and to ensure that its behavior exactly duplicates the behavior of the real tissue. If this can be achieved then VR systems can be used not only to train surgeons but also to rehearse individual procedures where variations in anatomy or pathology present specific surgical problems. The European Union has recently funded a multinational 3-year project (IERAPSI, Integrated
Environment for Rehearsal and Planning of Surgical Interventions) to produce a virtual reality
system for surgical training and for rehearsing individual procedures. Building the IERAPSI system will bring together a wide range of experts and combine the latest technologies to produce a true, patient specific virtual reality surgical simulator for petrous/temporal bone
procedures. This article presents a review of the “state of the art” technologies currently available to construct a system of this type and an overview of the functionality and specifications such a system requires
Modelling of electrochemistry and mass transport in polymer electrolyte membrane fuel cells, PEMFC
Get PDFIn this paper we present a modified version of the well know model of Bernardi and Verbrugge which was developed to simulate the behavior of Polymer Electrolyte Fuel Cell. The modified version is based on a different treatment of the electrokinetic model equations, the Butler-Volmer equations. Such equations are analytically integrated in the reactive regions of the electrodes, eliminating the main non-linear terms in the full mathematical model. It is shown that the modified Bernardi-Verbrugge is as accurate as the original model, that it allows an extension of the cell current density over which it is possible to find solutions, that the full numerical procedure is very stable, and that the simulations are up to three order of magnitude faster than those performed with the original model
Inversion of EM38 electrical conductivity data
Get PDFIn geophysical prospecting and environmental monitoring, the frequency domain electromagnetic induction technique has been developed for measuring the apparent soil electrical conductivity. A linear model can be formulated to described the response of the EM38, a ground conductivity meter. To image the subsurface conductivity profile from recorded data, the model has been inverted defining a Least Squares problem with Tikhonov approach improves the conditioning of the resulting linear systems, profile reconstruction can be surprisingly far from the expected conductivity behaviour