CRS4 Report

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https://hdl.handle.net/11050/59

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A 1D numerical study of the salt diffusion in a solar pond using finite difference tecniques
(2002-09-06) Leonardi, Erminia; Angeli, Celestino
A simple one dimensional (1D) model for the study of the salt diffusion processes in a solar pond is presented together with the implementation in a computer program using standard finite differences technique. The convective motions are not explicitly taken into account in this model and comments on their importance are presented. Albeit its simplicity the approach here reported can shed light on the basic effects taking place in the dynamics of a solar pond. The importance of the temperature profile and of the Soret effect is discussed.
A beam window target design with independent cooling for the EADF
(2000-11-30) Aragonese, Cosimo; Buono, Stefano; Fotia, Giorgio; Maciocco, Luca; Moreau, Vincent; Sorrentino, Luca
This report summarizes the study and the design of the window type target for the Energy Amplifier Demonstration Facility (EADF) [1]. The behaviour of the system in different condition has been analysed though extensive CFD simulations performed with the Star-CD commercial code [2]. The target represents one of the main technological problems related not only to the design of the EADF, but to all High Power Spallation Sources (HPSS) currently under study or in construction world-wide [4],[5]. Different configurations of the spallation EADF target are possible. Advantages and disadvantages of the different options are discussed elsewhere [6] and they are studied and analysed separately. The target device studied in this report is a window type target, cooled by diathermic oil in an independent loop. This target configuration is completely independent from the core operating conditions and gives advantages in terms of flexibility in the operation. The result of this report is a set of design data and constraints to take into account while engineering the spallation target.
A common description for surface-tension and diﬀusion in two-component ﬂows
(2010-08) Moreau, Vincent
This report tries to develop a common representation for diffusion and surface tension in two components newtonian flows. First, we make some preliminary considerations: (1) the Navier-Stokes equations of a fluid with two immiscible components is derived from the single components equations.In this case, the surface tension arrives from external consideration; (2) we shortly review the Cahn-Hilliard and Allen-Cahn equations describing a phase separation process, the surface-tension being considered as the terminal part of this process; and (3) we report a conservative representation of the surface tension and some of its variants. Second, we reinterprete the conservative form of the single components as also valid for miscible fluids. Making an hypothesis common in diffusion phenomena, we make the surface tension naturally appear from the single phase equations. An anti-diffusive term connected with the surface tension is put in evidence. Compatibility with diffusion is discussed.
A comparative study on binary scientific data formats
(1997-10) Leone, Andrea O.; Gobbetti, Enrico
In this technical report a set of binary scientific data formats are examined. They will be presented by examining their main functionally and features.
A comparative study on modular visualization environments
(1997-10) Gobbetti, Enrico; Leone, Andrea O.
Modular Visualization Environment (MVE) systems constitute a particular class of Visualization Packages. They are not visualization programs, but rather environments to build visualization applications, accordingly to specific needs of data representation. It is now clear that MVE belong to the class of general purpose Visualization Packages, because this is the main property that characterize them. From the end-user point of view, MVE are extemely versatile and flexible. In many cases, setting up a personalized representation of data simply consists in interconnecting in a network a number of pre-existing modules with atomic functionality, creating the specific visualization pipeline that ends with the rendering of the data. The longer is the list of available modules, the bigger is the number of different visualization applications the user can build in the MVE. The following MVEs are reviewed in this document: Application Visualization System (AVS), by Advanced Visual Systems Inc., Data Explorer, by IBM Inc., and IRIS Explorer, by NAG Ltd.
A CRS4 spallation Target for ESS Simulations with starccm+V5.0
(2010-07-16) Moreau, Vincent
In this document, we present a series of CFD simulations performed with starccm+V5 to build a sound proposal of windowless channel spallation target for ESS. The simulations increase progressively in complexity. The first simulation is a simple Mercury loop under the effect of a pulsed proton beam. The second one also includes a Hg/vacuum dynamic interface, using the VOF algorithm. The last simulations consider a LBE loop under vacuum subject to the thermal interaction with a proton beam, and is the basis for the proposal to ESS, still using the VOF algorithm. The simulation could be completed in a satisfactory way thanks to the use of a specific sharpening algorithm. This algorithm is explained and commented. The last simulations implementation is also described in details. The final results are shown. They appear very satisfying because the sharpening algorithm performs very well without giving rigidity to the free-surface and because the design elaborated seems a very promising basis for an ESS spallation target.
A distance learning environment architecture
(2000) Sommaruga, Lorenzo; Catenazzi, Nadia; Giroux, Sylvain; Moulin, Claude
This paper presents the core architecture of NURAXI, a multimedia research platform aimed at the design, generation, deployment, management and use of intelligent distance learning environments. It describes the actors and services that are involved in the production and use of intelligent distance learning environments, the structures that are at the heart of the environment, and the processes that use these structures. The competence notion is the central component around which both author's and student's interactions gravitate. An author generates the training material on the basis of competencies to be acquired by a student, and the means to get them, i.e. the related activities and contents. A student accesses the pedagogical material by first selecting his/her learning objectives. The training path is made of dynamically created pedagogical activities. Examples of implemented activities are also shown in the paper. The platform presents a number of interesting features including re-usability of didactic components; adaptability of the training material to the student model; dynamic definition of the training path; modularity, and interoperability thanks to the adoption of standard and open solutions in terms of document structures, ontologies, design and implementation techniques. All these advantages derive from the integration of technologies such as the XML paradigm, Servlets, Software Agents, and Distributed Databases.
A distributed heterogeneous image server
(1998) Loddo, Sergio; Brelstaff, Gavin; Zanetti, Gianluigi
Digital image transmission is now ubiquitous across computer networks and thus there is increasing pressure to allow access to medical image data at sites remote from PACS locations. In fact, it may soon make economic sense to outsource medical image services - to dedicated service providers at geographical locations outside of the traditional radiology department or HIS’s. The technical challenge faced by system developers is to produce client-Viewer/server-PACS configurations that can realistically span the network. In particular, the systems must provide the performance usually expected by client medics and it must be flexible to the needs of the service providers. At CRS4 - BioMedical Applications - we are integrating various technologies derived from the www-intranet field, and object-oriented middleware to prototype technological solutions that address both the issues of performance and flexibility. These are discussed in turn below; then we provide an overview of our system.
A first analysis of the solar trough transient
(2007-04) Massidda, Luca
A simplified analysis of the transient in a CSP plant that using a gas as a Heat Transfer Fluid is discussed.
A heat exchanger design for the separated window target of the EADF
(2000) Aragonese, Cosimo; Buono, Stefano; Fotia, Giorgio; Maciocco, Luca; Moreau, Vincent; Sorrentino, Luca
The spallation target of the Energy Amplifier Demonstration Facility (EADF) [1] is cooled by a liquid lead-bismuth eutectic (LBE), while the secondary coolant is a diathermic oil. The reasons for these choices have been extensively discussed in [2] and [3]. Here we present the design and the optimisation of a heat exchanger using these fluids, whose additional requirements are the need of fitting into the top of the annular downcomer section of the target and the minimisation of the pressure losses on the LBE side, allowing the use of natural convection for the circulation of the primary fluid. Heat exchanger working temperatures are between 250 and 180°C in the LBE side, and between 150 and 190°C in the oil side (cold fluid), while the power to be removed is up to 3 MW. We selected a bayonet-type heat exchanger, as suggested in [4] for the primary loop of the EADF vessel, which seems to be the most appropriate choice to satisfy all the requirements.
A modular approach to the Korba aquifer seawater intrusion study, 1, GIS field data analysis
(1998) Giacomelli, Andrea; Khlaifi, Ihsen; Tarhouni, Jamila; Paniconi, Claudio
Seawater intrusion is an important environmental problem in the coastal aquifers of many Mediterranean countries. In the 438 km2 Korba aquifer in eastern Tunisia, a large increase in the number of pumping wells for irrigation purposes since the 1960s has resulted in a lowering to below sea level of the water table in several observation piezometers, and in a consequent deterioration of the water quality. Several remediation scenarios are being considered for this region, including rationalization and control of water pumping from the wells, artificial recharge of the aquifer and construction of small dams to serve as an alternative source of irrigation water. In order to investigate the impact of these measures on the aquifer water quality, a GIS-based modeling study is being undertaken. The available data set comprises a number of layers of geographical information, giving a complete hy-drogeological characterization of the region, and time series of chemical and hydrologic variables acquired during several ground sampling campaigns performed in the last thirty years. The GIS is used to organize this heterogeneous data structure and to control the data flow through various phases of the work, i.e. the pre-processing of input data for the model, the interpretation of model outputs, and the calibration of the model itself. The GIS serves also as a support tool in the genera-tion of the 3-D computational grid used in the numerical simulations. In addition to describing the data structure and the organization of the system, the paper illustrates also the implementation of a simple recharge optimization scenario.
A multi modal interface for a visually impaired pupils educational environment
(2003-04) Pintus, Antonio; Lai, Cristian; Moulin, Claude; Archambault, Dominique
The aim of this paper is to describe a multi modal user interface integrated within an architecture allowing visually impaired pupils and sighted people to work on the same station. This architecture is developed to face the problem of the inclusion of visually impaired pupils in mainstream education. The system is able to display the same original multi-media content converted in different ways on screen, Braille terminal and vocal synthesizers. It accepts various interactions from keyboard, Braille bar and mouse. Both blind and sighted users can manage the same tools, cooperate together on the same content, and thus perform the same activities. Blind pupils may be assisted by sighted teachers or tutors that don’t know how to read Braille characters.
A Note on The Reﬂection and Transmission Law of an Incident Wave
(2007-02) Bonomi, Ernesto
In this paper is presented the classical boundary value problem of obliquely incident compressional plane waves impinging the interface between two homogeneous acoustic media. Each incident wave gives rise to reﬂected and transmitted components satisfying Snell’s law. The reﬂection is usually quantiﬁed by the reﬂection coeﬃcient, simply deﬁned, on each point of the interface, as the ratio of the reﬂected and incident wave amplitudes.
A numerical analysis of a high temperature solar collecting tube, using helium as an heat transfer fluid
(2007-06) Massidda, Luca; Varone, Alberto
This article analyses the use of a gas as a heat transfer fluid in the absorber tube. The fluid dynamics of the gas in the pipe, the heat-transfer in the system and the stresses and deformations of the pipe structure have been simulated numerically. The resulting flow characteristics, temperature distributions and stresses for a reference test case are discussed, and some possible solutions to enhance the system performance are analyzed.
A parallel spectral element method for applications to computational mechanics
(2001) Maggio, Fabio; Massidda, Luca; Sabadell, Javier; Siddi, Giuliana
We present a fully unstructured, parallel spectral element method based on domain decomposition. The implementation aims at improving accuracy and performance of a large number of applications in computational mechanics. We accomplish this target by merging the high accuracy of spectral methods with the flexibility of finite elements in treating problems with complex geometry. Parallelism is coarse grain and exploited at the algebraic level: the global linear system is distributed among processors, and then solved by iterative techniques. For evolutive problems it is possible to adopt explicit time-marching schemes, thus resulting in very competitive performances. We provide a couple of numerical experiments, based on the Helmholtz equation and the acoustic problem, and give a measure of accuracy and efficiency, illustrating the method in both steady and evolutive problems.
A Perl-C++ interface with applications to the QT library
(2002) De Leo, Roberto
In this paper we present the parser we wrote to produce automatically Perl bindings for C++ libraries.
A shapes based geometric modeler for mesh++, API description
(1999-07-03) Camba, Monica; Pili, Piero; Zanetti, Gianluigi
One of the purposes of the ViVa Project is the reconstruction of geometrical models from a suitable set of data provided by non invasive medical analyses like Computed Tomography (CT) or Magnetic Resonance Imaging (MRI). To do this, we first segment the vessel geometry from the data sets using techniques such as active snakes, and then reconstruct geometrical models using the XOX SHAPES geometric modeler, and in particular its MicroTopology features. In order to perform blood flow simulation on these models, we need to mesh them, and so we use the Mesh++ grid generator to process the models and create a two-dimensional grid for the surfaces and a three-dimensional one for the vessel lumen.
A thermal fluid-dynamic steady state analysis of the EADF downcomer channel
(2000-04-04) Aragonese, Cosimo; Buono, Stefano; Fotia, Giorgio; Maciocco, Luca; Moreau, Vincent; Sorrentino, Luca
In this work a numerical simulation of the Energy Amplifier Demonstration Facility (EADF) [1, 2] downcomer channel is presented. The simulation is fully three-dimensional (3D) and is focused on a Steady-State Analysis. All relevant heat transfer phenomena are taken into account. The Intermediate Heat eXchangers (IHX) of the EADF reference configuration are immersed in the lead-bismuth eutectic of the downcomer and no physical barrier separates the hot and cold collectors. As expected, the simulation shows a thermal stratification outside the IHX, whose characteristics mainly depend on the IHX pressure loss. A parametric study of the effects of the IHX pressure loss coeficient on the thermal stratification pattern is presented.
A thermal fluid-dynamic transient analysis of the EADF down-comer channel
(2000-12-05) Aragonese, Cosimo; Buono, Stefano; Fotia, Giorgio; Maciocco, Luca; Moreau, Vincent; Sorrentino, Luca
In this work a numerical simulation of the downcomer channel of the Energy Amplifier Demonstration Facility (EADF) [1, 2] is presented. The simulation is fully three-dimensional (3D) and is focused on a transient analysis. All relevant heat transfer phenomena are taken into account. Starting from the nominal power configuration, we have simulated the response of the system to a power shutdown of the core for a period of 60 s. The core shutdown is simulated imposing a linear variation of the inlet flow temperature from 400°C to 305°C in 10 s. The simulation shows the evolution of the thermal stratification outside the IHX and the evolution of the IHX operation.
A velocity model inference from the inversion of 3d-zero-offset seismic traces in the space-frequency domain
(2004-03) Pieroni, Enrico; Bonomi, Ernesto; Lahaye, Domenico
We proposed a new algorithm for the reconstruction of the scalar velocity field of a subsoil from post-stack seismic data. The algorithm is based on a non-linear Lagrangian framework in which direct and adjoint equations are solved by demigrating and migrating in the frequency domain respectively. We presented encouraging preliminary results for 1D synthetic test cases. Future work is required to extend this work in 2D and 3D

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