Numerical prediction of sloshing loads in flexible tanks

The scope of the presentation is to review our ongoing research on the numerical modeling of sloshing in deformable tanks

Confronto SEM-FEM per un problema di dinamica strutturale

In questo rapporto si è voluto affrontare un problema classico di ingegneria civile, quello di una trave semplicemente appoggiata sollecitata da una forza impulsiva di mezzeria. Il problema in esame, ben noto dal punto di vista sia sperimentale che teorico è stato utilizzato per verificare l’applicabilità delle metodologie ad elementi spettrali, alla risoluzione di un problema di semplice dinamica strutturale. La metodologia SEM (Spectral Element Method) è stata implementata dal gruppo di Meccanica dei Solidi e delle Strutture nella famiglia di codici ELSE, finora queste metodologie sono state impiegate in ambito strutturale, per la risoluzione di problemi statici, e di dinamica transiente “veloce” legata cioè alla propagazione di onde elastiche nelle strutture. I fenomeni dinamici in questo caso sono più lenti, interessano frequenze inferiori, e vengono genericamente definiti come problemi di dinamica strutturale. I risultati ottenibili con la metodologia spettrale saranno confrontati con quelli ottenibili con una specifica metodologia ad elementi finiti, implementata nel codice commerciale ANSYS, di provata affidabilità

Fluid-solid interaction modeling for sloshing flows in flexible tanks

The scope of the presentation is to review our ongoing research on the numerical modeling of sloshing in deformable tanks

Phenomenology of liquid metal thermal-hydraulics

The cooling system of the Energy Amplifier (EA) is based on a Lead flow driven by natural circulation [1]. In the Energy Amplifier Demonstration Facility (EADF) a Lead-Bismuth eutectic is used and natural circulation, although enhanced through a gas injection system, is the pumping force for the cooling of both the target (only in the case of the window-type target) and the primary circuit[2]. Numerical simulation is extensively used for the design and analysis of these flows, using both commercial and in-house codes. However, liquid metals properties are very different from that of common fluids, so the physical models to be used in the simulations should be carefully assessed. In general the numerical simulation of any kind of flow requires: (i) the thermodynamic modelling of the fluid; (ii) the fluid dynamics governing equations; (iii) the turbulence modelling. In this work the thermodynamic model for heavy liquid metals is presented, starting with the derivation of the equations of state for a general fluid from the basic laws of thermodynamics. This thermodynamic model is then used for the analysis of a one-dimensional natural convection loop, in order to put in evidence the main physical mechanisms governing this particular kind of flow and the simplifications that can be applied to the one dimensional governing equations. An extensive analysis of the tree-dimensional fluid dynamic governing equations and of the turbulence models for liquid metal flows can be found in [7] and [8] respectively

Numerical methodologies for the simulation of liquid metal flows

The fluid-dynamic modelling for the simulation of the Lead-Bismuth flow in the EADF was reviewed. The general form of the non-dimensional governing equation was derived, and the analysis of the orders of magnitude of the different terms in the case of a the liquid metal flows in the EADF was performed, through a flow-Mach number asymptotic analysis. It was found that the resulting form of the equations is the one commonly used in commercial CFD codes for the simulation of liquid flows, which can then be used for our applications. The most common numerical methods for flow-Mach number applications were also presented. These methods are general and can be applied to liquid metal flows without any modification. The peculiarity of the numerical simulation of liquid metal flows lies in the modelling of the turbulent heat transfer, due to the flow Prandtl number of this type of fluids. This subject is discussed in [21]

Integration of numerical tools for the combined thermal-hydraulics and structural analysis of energy amplifier components

The CRS4 R&D activity on the Energy Amplifier Demonstration Facility (EADF) [1] concerns the thermal fluid-dynamic and structural computational analysis in support to the design of some of the crucial components of the machine. We are currently studying the operating conditions of the spallation target [2-3] and the sub-critical core [4-5], including steady state, transient [31-32] and accidental conditions. The simulation activity also includes the analysis of multi-phase (liquid-gas systems with high void fractions) [6-7] and free surface Liquid Metal (LM) flows [8-9]. A parallel activity of benchmarking of numerical codes on LM experiments is in progress [10-12, 33-34], joined with a critical theoretical review of numerical models applied to LM flows [13-15]

Numerical studies related to the design of the beam target of the energy amplifier prototype

The Centre for Advanced Studies, Research and Development in Sardinia (CRS4) is participating in an Italian R&D program, together with Ansaldo, ENEA and INFN, devoted to the design of a 80 MW prototype of the Energy Amplifier proposed by C. Rubbia et al.. The use of advanced numerical tools has been of practical support in the design of critical elements of the machine such as the fuel element and the beam target. The aim of this work is to show the design and optimization of the Liquid Metal Spallation Target, which consists in an axial-symmetric vertical cylinder, where a Pb-Bi eutectic, in a natural convection driven flow regime, works at the same time as spallation material and coolant for the target and the beam window. The most critical part of the target is the window itself, where the highest temperatures and thermal stresses are reached. The minimization of such temperatures and stresses is the goal of the optimization. The main geometrical dimensions of the target (i.e. beam pipe, beam window and external container) are somehow fixed since they are related to the proton beam distribution and to the EA core design. The optimization therefore acts on the suitable design of the flow guide which separates the hot rising flow from the cold one. In the region where the flow is heated by the proton beam the flow guide has a funnel shape which accelerates the liquid metal. The numerical simulations are performed by using three different tools. The FLUKA Montecarlo code is used to calculate the heat source distribution in the window and in the coolant generated by the interaction with the proton beam. The results of these calculations are used as input data for the thermal fluid dynamic simulations performed with the STAR-CD commercial software. The resulting temperature and pressure fields are finally introduced in the NASTRAN code used for the structural analysis of the solid components

Structural response of the EADF target beam window to beam interruptions: transient thermo-mechanical computation

The 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]

Thermo-mechanical stresses on the beam window

The Centre for Advanced Studies, Research and Development in Sardinia (CRS4) is participating to an Italian R&D program, together with Ansaldo, ENEA and INFN, devoted to the design of a 80 MW prototype of the Energy Amplifier proposed by C. Rubbia. The use of advanced numerical tools has been of practical support in the design of critical elements of the machine such as the fuel element and the beam target. The aim of this work is to study the sensitivity of beam window stresses to the beam distribution, size and interruption. In order to compute thermal stresses, the heat deposition in the window and in the coolant generated by the interaction with the proton beam is calculated and used as input data for the fluid dynamic simulation of the natural convection flow of the target coolant

The effect of a high-grain diet on the rumen microbiome of goats with a special focus on anaerobic fungi

This work investigated the changes of the rumen microbiome of goats switched from a forage to a concentrate diet with special attention to anaerobic fungi (AF). Female goats were fed an alfalfa hay (AH) diet (0% grain; n = 4) for 20 days and were then abruptly shifted to a high-grain (HG) diet (40% corn grain, 60% AH; n = 4) and treated for another 10 days. Rumen content samples were collected from the cannulated animals at the end of each diet period (day 20 and 30). The microbiome structure was studied using high-throughput sequencing for bacteria, archaea (16S rRNA gene) and fungi (ITS2), accompanied by qPCR for each group. To further elucidate unclassified AF, clone library analyses were performed on the ITS1 spacer region. Rumen pH was significantly lower in HG diet fed goats, but did not induce subacute ruminal acidosis. HG diet altered prokaryotic communities, with a significant increase of Bacteroidetes and a decrease of Firmicutes. On the genus level Prevotella 1 was significantly boosted. Methanobrevibacter and Methanosphaera were the most abundant archaea regardless of the diet and HG induced a significant augmentation of unclassified Thermoplasmatales. For anaerobic fungi, HG triggered a considerable rise in Feramyces observed with both ITS markers, while a decline of Tahromyces was detected by ITS2 and decrease of Joblinomyces by ITS1 only. The uncultured BlackRhino group revealed by ITS1 and further elucidated in one sample by LSU analysis, formed a considerable part of the AF community of goats fed both diets. Results strongly indicate that the rumen ecosystem still acts as a source for novel microorganisms and unexplored microbial interactions and that initial rumen microbiota of the host animal considerably influences the reaction pattern upon diet change.Fil: Fliegerova, Katerina O.. Czech Academy of Sciences; República ChecaFil: Podmirseg, Sabine M.. Universidad de Innsbruck; AustriaFil: Vinzelj, Julia. Universidad de Innsbruck; AustriaFil: Grilli, Diego Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; Argentina. Universidad Nacional de Cuyo. Facultad de Cs.médicas. Departamento de Patología. Area de Microbiología; ArgentinaFil: Kvasnová, Simona. Czech Academy of Sciences; República ChecaFil: Schierová, Dagmar. Czech Academy of Sciences; República ChecaFil: Sechovcová, Hana. Czech Academy of Sciences; República ChecaFil: Mrázek, Jakub. Czech Academy of Sciences; República ChecaFil: Siddi, Giuliana. Università degli Studi di Sassari; ItaliaFil: Arenas, Graciela Nora. Universidad Nacional de Cuyo. Facultad de Cs.médicas. Departamento de Patología. Area de Microbiología; ArgentinaFil: Moniello, Giuseppe. Università degli Studi di Sassari; Itali