259 research outputs found

    Advanced SBAS-DInSAR technique for controlling large civil infrastructures: an application to the Genzano di Lucania dam

    Get PDF
    Monitoring surface deformation on dams is commonly carried out by in situ geodetic surveying, which is time consuming and characterized by some limitations in space coverage and frequency. More recently microwave satellite-based technologies, such as advanced-DInSAR (Differential Synthetic Aperture Radar Interferometry), have allowed the integration and improvement of the observation capabilities of ground-based methods thanks to their effectiveness in collecting displacement measurements on many non-destructive control points, corresponding to radar reflecting targets. The availability of such a large number of points of measurement, which are distributed along the whole structure and are characterized by millimetric accuracy on displacement rates, can be profitably adopted for the calibration of numerical models. These models are implemented to simulate the structural behaviour of a dam under conditions of stress thus improving the ability to maintain safety standards. In this work, after having analysed how advanced DInSAR can effectively enhance the results from traditional monitoring systems that provide comparable accuracy measurements on a limited number of points, an FEM model of the Genzano di Lucania earth dam is developed and calibrated. This work is concentrated on the advanced DInSAR technique referred to as Small BAseline Subset (SBAS) approach, benefiting from its capability to generate deformation time series at full spatial resolution and from multi-sensor SAR data, to measure the vertical consolidation displacement of the Genzano di Lucania earth dam

    Analysis of transition for a flow in a channel via reduced basis methods

    Get PDF
    The study of the flow mechanisms leading to transition in a planar channel flow is investigated by means of a reduced basis method known as Dynamic Mode Decomposition (DMD). The problem of identification of the most relevant DMD modes is addressed in terms of the ability to (i) provide a fairly accurate reconstruction of the flow field, and (ii) match the most relevant flow structures at the beginning of the transition region. A comparative study between a natural method of selection based on the energetic content of the modes and a new one based on the temporal dynamics of the modes is here presented

    Validating a timing simulator for the NGMP multicore processor

    Get PDF
    Timing simulation is a key element in multicore systems design. It enables a fast and cost effective design space exploration, allowing to simulate new architectural improvements without requiring RTL abstraction levels. Timing simulation also allows software developers to perform early testing of the timing behavior of their software without the need of buying the actual physical board, which can be very expensive when the board uses non-COTS technology. In this paper we present the validation of a timing simulator for the NGMP multicore processor, which is a 4 core processor being developed to become the reference platform for future missions of the European Space Agency.The research leading to these results has received funding from the European Space Agency under contract NPI 4000102880 and the Ministry of Science and Technology of Spain under contract TIN-2015-65316-P. Jaume Abella has been partially supported by the Ministry of Economy and Competitiveness under Ramon y Cajal postdoctoral fellowship number RYC-2013-14717.Peer ReviewedPostprint (author's final draft

    Real-time regional jet comprehensive aeroicing analysis via reduced order modeling

    Get PDF
    This paper presents a reduced-order modeling framework based on proper orthogonal decomposition, multidimensional interpolation, and machine learning algorithms, along with an error-driven iterative sampling method, to adaptively select an optimal set of snapshots in the context of in-flight icing certification. The methodology is applied, to the best of our knowledge for the first time, to a complete aircraft and to the entire icing certification envelope, providing invaluable additional data to those from icing tunnels or natural flight testing. This systematic methodology is applied to the shape/mass of ice and to the aerodynamics penalties in terms of lift, drag, and pitching moments. The level of accuracy achieved strongly supports the drive to incorporate more computational fluid dynamics information into in-flight icing certification and pilot training programs, leading to increased aviation safety


    Get PDF
    Le giunzioni metalliche incollate offrono diversi vantaggi nei confronti dei tradizionali collegamenti meccanici (rivettatura, bullonatura, ecc.), tuttavia richiedono un’estensiva caratterizzazione meccanica al fine di garantire un’adeguata affidabilità delle strutture in cui vengono inserite. In questo lavoro si presentano i risultati delle prove sperimentali e delle simulazioni numeriche condotte nell’ambito della riprogettazione di una giunzione rivettata di un componente reale, sfruttando la tecnologia dell’incollaggio. L’adesivo usato ù una resina epossidica bicomponente, caratterizzata attraverso una campagna di prove sperimentali e simulazioni numeriche, su provini di tipo single-lap e T-peel. Si presenta quindi un confronto, sia numerico che sperimentale, delle prestazioni meccaniche della giunzione rivettata con l’analoga giunzione incollata. I risultati hanno evidenziato un sostanziale miglioramento in termini di rigidezza e resistenza con l’uso della tecnica dell’incollaggio

    Numerical simulations of an explosion confined inside a cylindrical pipe made of aluminium alloy Al6061-T6

    Get PDF
    Simulation of the behaviour of structural components subjected to high explosive detonation is one of the current challenges in the field of numerical simulation. Along with experimental tests, numerical analysis is necessary to give an in-depth insight of this event, as well to reduce costs for some further experimental tests. High values of strain rate, temperature and pressure, together with failure phenomenon, govern the complex interaction between the explosion and the structure involved. In a scenario of this type, capabilities and performance of the numerical software used are crucial to the quality and the outcome of the simulation. Besides the simulation itself, this paper provides a comparison between different finite element programs such as ABAQUS, AUTODYN and LS-DYNA in an explosion event. In the event descibed in the paper, the behaviour of tube made of aluminium alloy Al6061-T6 and filled with explosive material is under investigation. A fully coupled Eulerian and Lagrangian formulation is used together with a complete mechanical behaviour and constitutive equations of all the materials involved in the simulation (aluminium alloy Al6061-T6, explosive C4, air). Finally, results and comparison between the mentioned numerical solvers will be reported and critically discussed

    Turbulence Chemistry Interaction via Eddy Dissipation Model for Scramjet Analysis and Design

    Get PDF
    This paper considers the Eddy Dissipation Model to address the combustion process inside scramjet engines designed to operate at high flight Mach numbers. The aim is to demonstrate the most appropriate use of the model for design purposes. To this end, two hydrogen-fueled experimental scramjet configurations with different fuel injection approaches are studied numerically. In the case of parallel fuel injection, it is demonstrated that relying on estimates of ignition delay from a one-dimensional kinetics program can greatly improve the use of the EDM. In the second case, the transverse injection of hydrogen resulted in an overall good agreement of the model with experimental pressure traces except in the vicinity of the injection location. Overall, the EDM appears to be a suitable tool for scramjet combustor design incorporating a parallel or transverse fuel injection mechanism

    Adaptive data-driven model order reduction for unsteady aerodynamics

    Get PDF
    A data-driven adaptive reduced order modelling approach is presented for the reconstruction of impulsively started and vortex-dominated flows. A residual-based error metric is presented for the first time in the framework of the adaptive approach. The residual-based adaptive Reduced Order Modelling selects locally in time the most accurate reduced model approach on the basis of the lowest residual produced by substituting the reconstructed flow field into a finite volume discretisation of the Navier−Stokes equations. A study of such an error metric was performed to assess the performance of the resulting residual-based adaptive framework with respect to a single-ROM approach based on the classical proper orthogonal decomposition, as the number of modes is varied. Two- and three-dimensional unsteady flows were considered to demonstrate the key features of the method and its performance

    Contention-aware performance monitoring counter support for real-time MPSoCs

    Get PDF
    Tasks running in MPSoCs experience contention delays when accessing MPSoC’s shared resources, complicating task timing analysis and deriving execution time bounds. Understanding the Actual Contention Delay (ACD) each task suffers due to other corunning tasks, and the particular hardware shared resources in which contention occurs, is of prominent importance to increase confidence on derived execution time bounds of tasks. And, whenever those bounds are violated, ACD provides information on the reasons for overruns. Unfortunately, existing MPSoC designs considered in real-time domains offer limited hardware support to measure tasks’ ACD losing all these potential benefits. In this paper we propose the Contention Cycle Stack (CCS), a mechanism that extends performance monitoring counters to track specific events that allow estimating the ACD that each task suffers from every contending task on every hardware shared resource. We build the CCS using a set of specialized low-overhead Performance Monitoring Counters for the Cobham Gaisler GR740 (NGMP) MPSoC – used in the space domain – for which we show CCS’s benefits.The research leading to these results has received funding from the European Space Agency under contracts 4000109680, 4000110157 and NPI 4000102880, and the Ministry of Science and Technology of Spain under contract TIN-2015-65316-P. Jaume Abella has been partially supported by the Ministry of Economy and Competitiveness under Ramon y Cajal postdoctoral fellowship number RYC-2013-14717.Peer ReviewedPostprint (author's final draft