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Structural response of the EADF target beam window to beam interruptions: transient thermo-mechanical computation
Get PDFThe operability of a high power proton beam target in an Accelerator Driven System (ADS) is
strictly connected to the structural integrity of the beam window, which is undoubtedly the most
delicate component in such devices, being exposed to the combined effects of high intensity proton
and neutron irradiation, liquid metal corrosion and high thermal stresses induced by the interaction
with the beam. It has also recently been highlighted that beam trips may frequently occur in current
high power accelerators [1]. Clearly, the definition of the requirements of future accelerators depends
on the behaviour of the window under such conditions. For this purpose a numerical study of typical
transients has been carried out on the 600 MeV proton beam target that drives the 80 MW
Demonstration Facility of the Energy Amplifier proposed by C. Rubbia, [2] presently under
development in Italy by Ansaldo, CRS4, ENEA and INFN [3]
Studio di un S.I. per la gestione delle emergenze in seguito a eventi calamitosi in Sardegna
Get PDFLa simulazione di situazioni di rischio derivanti da eventi calamitosi estesi è necessaria al fine di
individuare le più rapide vie di accesso all'area colpita da parte dei mezzi e delle squadre di soccorso a
terra e di indicare alle autorità preposte le vie di fuga ed evacuazione rapida delle persone verso zone
sicure. Vi sono però alcune tipologie di incidenti, come ad esempio gli incendi o le emissioni tossiche,
per le quali risulta difficoltoso stabilire a priori strategie generali di intervento, a causa della
dipendenza da una moltitudine di fattori determinabili solo al momento dell'evento. In questi casi, un
importante contributo allo studio di scenari di rischio può essere dato dall'impiego di modelli di
evacuazione che forniscano una base preliminare, svincolata da eventi specifici, tesa a evidenziare le
zone più critiche in funzione della distribuzione della popolazione e delle caratteristiche delle
infrastrutture. Viene presentato un caso di studio relativo all'area industriale di Predda Niedda (Sassari).The simulation of disasters arising from hazardous events is necessary in order to identify the fastest
access routes to the affected zones and to provide indications on the possible safety routes. However,
there are several types of accidents, such as firestorms or toxic spills, for which the a priori definition
of general emergency strategies appears problematic, due to dependence on many factors which can be
assessed only at the time of the event. In such cases, an important support in the analysis of accident
scenarios can be given by the use of community evacuation models independent of any hazard or zone,
which can be employed to identify the spatial variation in evacuation difficulty taking into account only
the distribution of the population and the existing infrastructure. The model described has been applied
to a case study for the industrial area of Predda Niedda (Sassari)
BRITE-euram LowNOx III. Theme V, task 2: reduced reaction mechanisms: CRS4 final deliverable
No full textThe present documents reports about CRS4 activity for the task 2 of the theme V of the LowNOx III project. In this chapter a summary of what has been done at CRS4 during this time is presented. In the following chapters a description of the physical models and computational tools used for the calculation is done. In chapter 2 the combustion model specially implemented to afford calculation of combustion flows in different combustion regimes is presented. Chapter 3 and 4 concern the combustion model validation. Chapter 5 and 6 present ILDM and classical approaches to reduced chemistry. ILDM software testing is proposed in chapter 7. A simple application of Combustion model package EDC+PSR, developed for the CFX code, is presented in chapter 8. Finally a series of appendixes gives the necessary documentation for the EDC+PSR software package
Specification of the inverse problem
No full textWe address the problem of time-domain inverse scattering, where we want to determine some unknown characteristics of an object from measurements of the reected field. The IMPACT inverse method is described first in a general case in section 1 and then applied to three different solvers for vibro-acoustics, pure acoustics and electromagnetics in sections 2-4. In section 5 the optimisation problem and the structure of the code is discussed. Relating to the workplan, section 1 corresponds to task 1.5, sections 2-4 to the tasks 1.2 and 1.3 and section 5 to task 1.4. The description of the direct codes are
kept in appendices A-C. The contents of section 1-5 are summarised
Exploring virtual prototypes using time-critical rendering
No full textWe present an application of our time-critical multiresolution rendering algorithm to the visual and possibly collaborative exploration of large digital mock-ups. Our technique relies upon a scene description in which objects are represented as multiresolution meshes. We perform a constrained optimization at each frame to choose the resolution of each potentially visible object that generates the best quality image while meeting timing constraints. We present numerical and pictorial results of the experiments performed that support our claim that we can maintain a xed frame-rate even when rendering very large datasets on low-end graphics PCs
Catheter insertion simulation with combined visual and haptic feedback
Get PDFWe have developed an experimental catheter insertion system supporting head-tracked stereoscopic viewing of volumetric reconstruction registered with direct haptic 3D interaction. The system takes as input patient data acquired with standard medical imaging modalities and regards it as a visual and haptic environment whose parameters are defined using look-up tables. By means of a mirror, the screen seems to be positioned like a surgical table providing the impression of looking down at the patient in a natural way. Co-registering physical and virtual spaces beforehand means that the patient appears at a fixed physical positionj on the surgical table and inside the workspace of the PHANToM device which controls catheter insertion. During the insertion procedure the system provides perception of the force of penetration and positional deviation of the inserted catheter
Spatial distribution of chaotic transients in unidirectional synchronization
Get PDFWe consider the transient time to synchronisation in unidirectionally coupled dynamical systems, both discrete maps and continuous flows. We note that while in certain systems the time distribution is typical of chaotic transients, in other cases the distribution possesses a specific spatial organization.175-181Pubblicat
Coupled surface runoff and subsurface flow model for catchment simulations
Get PDFA distributed catchment scale numerical model for the simulation of coupled surface
runoff and subsurface flow is presented. Starting from rainfall (evaporation) records, the model first determines the infiltration (exfiltration) rates in the soil, by evaluation of the soil field capacity at the specific conditions as calculated from the three-dimensional solution of the variably-saturated groundwater flow model (Richards’ equation). The flow rate that remains or returns to the surface, the so called overland flow, is then routed via a diffusion wave surface runoff model based on a Muskingum-Cunge scheme with variable parameters. Both hillslope and channel flow are described, and a special algorithm is used for the simulation of pools/lakes effects on storm-flow response.
The importance of including detailed subsurface flow description in catchment
simulations is shown on a simple testcase characterized by the presence of a central
depression.583-59
An object oriented flow solver for the CRS4 virtual vascular project
Get PDFThe CRS4 Virtual Vascular Project (ViVa) is aimed to the development of software tools for hemodynamic specialists and cardiovascular surgeons in order to study and interpret the information produced by non-invasive imaging equipment. The computational kernel of the ViVa system is a solver of the Navier-Stokes equations for viscous incompressible which govern the blood in large vessels(e.g. arteries). The computational strategy is based on the domain decomposition with the mortar element method. The mortar element method provides high encapsulation on the level of subdomain computations, i.e. subdomain meshes, matrices, preconditioners can be treated completely independently. This feature allows to implement the mortar method efficiently within the frames of the object oriented approach and C++ programming language. Thanks to the modularity of the code, in different subdomains we can use different meshes (hexagonal, tetrahedral), different matrix storage schemes (band, sparse), different preconditioners.
The flexibility in the choice of the subdomain numerical technique makes it possible
to construct computationally “optimal" applications, for instance, to use multigrid subdomain preconditioners, or to exploit coarser meshes, where the solution is smooth, etc. Thus a library of C++ classes has been developed, which can be used to build a required numerical model
Combustion model for industrial numerical simulations
Get PDFAn original model for numerical simulation of turbulent premixed and partially premixed combustion at large Re and Da numbers is described. A quantitative description of the coupling between turbulence and chemistry by the flamelet mechanism is proposed, based on the generalized Kolmogorov concept of small scale equilibrium structures in developed turbulence. A model equation for premixed combustion is described in the terms of a reaction progress variable. This model has been implemented in the commercial code FLUENT5, and is validated against the experients by V. Karpov (spherical flames in a well stirred reactor) and P.Moreau (high velocity combustion in a channel). Partially premixed combustion is modeled by transport equations for the PDF of passive concentration and the conditional progress variable. Results of numerical simulations with turbulence-chemistry coupling by equilibrium and laminar flamelet chemistry are compared with experimental data by Barlow and Frank