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Hérault, Alexis
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Hérault, Alexis
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alexis.herault@ingv.it
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33 results
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- PublicationRestrictedSPH modeling of dynamic impact of tsunami bore on bridge piers(2015-10)
; ; ; ; ; ; ;Wei, Z.; Department of Civil Engineering, Johns Hopkins University, Baltimore, MD 21218, USA ;Dalrymple, R.; Department of Civil Engineering, Johns Hopkins University, Baltimore, MD 21218, USA ;Herault, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Bilotta, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Rustico, E.; Bundesanstalt für Wasserbau, 76187 Karlsruhe, Germany ;Yeh, H.; School of Civil & Construction Engineering, Oregon State University, Corvallis, OR 97331, USA; ; ; ; ; The Smoothed Particle Hydrodynamics (SPH) method is applied to investigate the impact of a tsunami bore on simplified bridge piers in this study. This work was motivated by observations of bridge damage during several recent tsunami events, and its aim is to further the understanding of the dynamic interaction between a tsunami bore and a bridge pier. This study is carried out by simulating a well-conducted physical experiment on a tsunami bore impingement on vertical columns with an SPH model, GPUSPH. The influences of bridge pier shape and orientation on free surface evolution and hydrodynamic loading are carefully examined. Furthermore, the unsteady flow field that is around and in the wake of the bridge pier is analyzed. Finally, GPUSPH is applied to explore the hydrodynamic force caused by the bridge pier blockage, the wave impact on structures, and the bed shear stress around a bridge pier due to a strong tsunami bore.284 49 - PublicationRestrictedSemi-implicit 3D SPH on GPU for lava flows(2018-12-15)
; ; ; ; ; ; ; ; ; ; ; ; ;; ; GPUSPH is an implementation of Weakly-Compressible Smoothed Particle Hydrodynamics with an explicit predictor–corrector integration scheme, that takes advantage of the parallel nature of the method to run on Graphic Processing Units (GPUs). Despite the massive speed-up granted by the use of GPUs, the application of GPUSPH to the simulation of highly viscous fluids is still problematic, due to the severe time-stepping restrictions imposed by the explicit integration scheme when the viscous term becomes dominant. This is an issue in the simulation of lava flows, where the thermal-dependent rheology can lead to kinematic viscosities in the order of 104m2s−1 or more at low temperatures. To overcome this limitation, we introduce a semi-implicit integration scheme, where only the viscous part of the momentum equation is solved implicitly. Here we show the significant advantages of our approach in terms of simulation run times as well as better quality of the results over the fully explicit scheme.689 2 - PublicationRestrictedSPH MODELING OF LAVA FLOWS WITH GPU IMPLEMENTATION(2010)
; ; ; ; ; ;Hérault, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Bilotta, G.; Università degli studi di Catania ;Del Negro, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Russo, G.; Università degli studi di Catania ;Vicari, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; ; ; ; ; ; ; ;Fortuna, Luigi; Università degli studi di Catania ;Fradkov, Alexander; Institute for Problems of Mechanical Engineering ;Frasca, Mattia; Università degli studi di Catania; ; We describe the implementation of the Smoothed Particle Hydrodynamics (SPH) method on graphical processing units (GPU) using the Compute Unified Device Architecture (CUDA) developed by NVIDIA. The entire algorithm is executed on the GPU, fully exploiting its computational power. The code faces all three main components of an SPH simulation: neighbor list constructions, force computation, integration of the equation of motion. The simulation speed achieved is one to two orders of magnitude higher than the equivalent CPU code. Applications are shown for simulating the paths of lava flows during volcano eruptions. Both static problems with purely thermal effects (such as lava lake solidification) and dynamic problems with a complete lava flow were simulated.157 35 - PublicationOpen AccessSimulating complex fluids with smoothed particle hydrodynamics(2017)
; ; ; ; ; ; ; ; ; ; ; ; ;; ;Complex fluid dynamics encompasses a large variety of flows, such as fluids with non-Newtonian rheology, multiphase and multi-fluid flows (suspensions, lather, solid/fluid interaction with floating objects, etc.), violent flows breaking waves, dam-breaks, etc.), fluids with thermal dependencies and phase transition or free-surface flows. Correctly modeling the behavior of such flows can be quite challenging, and has led to significant advances in the field of Computational Fluid Dynamics (CFD). Recently, the Smoothed Particle Hydrodynamics (SPH) method has emerged as a powerful alternative to more classic CFD methods (such as finite volumes or finite elements) in many fields, including oceanography, volcanology, structural engineering, nuclear physics and medicine. With SPH, the fluid is discretized by means of particles and thanks to the meshless, Lagrangian nature of the model, it easily allows the modeling and simulation of both simple and complex fluids, simplifying the treatment of aspects that can be challenging with more traditional methods: dynamic free surfaces, large deformations, phase transition, fluid/solid interaction and complex geometries. In addition, the most common SPH formulations are fully parallelizable, which favors implementation on high-performance parallel computing hardware, such as modern Graphics Processing Units (GPUs). We present here how GPUSPH, an implementation of the SPH method that runs on GPUs, can model a variety of complex fluids, highlighting the computational challenges that arise in its applications to problem of great interest in volcanology.704 159 - PublicationRestrictedGPUSPH: a Smoothed Particle Hydrodynamics model for the thermal and rheological evolution of lava flows(2015-11-09)
; ; ; ; ; ;Bilotta, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Herault, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Cappello, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Ganci, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Del Negro, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; ; ; ; GPUSPH is a fully three-dimensional model for the simulation of the thermal and rheological evolution of lava flows that relies on the Smoothed Particle Hydrodynamics (SPH) numerical method. Thanks to the Lagrangian, meshless nature of SPH, the model incorporates a more complete physical description of the emplacement process and rheology of lava that considers the free surface, the irregular boundaries represented by the topography, the solidification fronts and the non-Newtonian rheology with temperature-dependent parameters. GPUSPH follows the very general Herschel–Bulkley rheological model, which encompasses Newtonian, power-law and Bingham flow behaviours, with both constant and temperature-dependent parameters, and can thus be used to explore in detail the impact of rheology on the behaviour of lava flows and on their emplacement. To illustrate this possibility, we present some preliminary applications of the model for studying the rheology of lava flows with different constitutive relationships and thermal regimes using the real topography of the Mt Etna volcano.211 37 - PublicationOpen AccessNumerical simulation of lava flow using a GPU SPH model(2011)
; ; ; ; ; ;Herault, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Bilotta, G.; Università di Catania, Dipartimento di Matematica e Informatica, Catania, Italy ;Vicari, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Rustico, E.; Università di Catania, Dipartimento di Matematica e Informatica, Catania, Italy ;Del Negro, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; ; ; ; A smoothed particle hydrodynamics (SPH) method for lava-flow modeling was implemented on a graphical processing unit (GPU) using the compute unified device architecture (CUDA) developed by NVIDIA. This resulted in speed-ups of up to two orders of magnitude. The three-dimensional model can simulate lava flow on a real topography with free-surface, non- Newtonian fluids, and with phase change. The entire SPH code has three main components, neighbor list construction, force computation, and integration of the equation of motion, and it is computed on the GPU, fully exploiting the computational power. The simulation speed achieved is one to two orders of magnitude faster than the equivalent central processing unit (CPU) code. This GPU implementation of SPH allows high resolution SPH modeling in hours and days, rather than in weeks and months, on inexpensive and readily available hardware.361 253 - PublicationRestrictedSimulation of Nearshore Tsunami Breaking by Smoothed Particle Hydrodynamics MethodThis study applies the numerical model GPUSPH, an implementation of the weakly compressible smoothed particle hydrodynamics (SPH) method on graphics processing units, to simulate nearshore tsunami processes. Two sets of laboratory experiments that involve violent wave breaking are simulated by the three-dimensional numerical model. The first set of experiments addresses tsunamilike solitary wave breaking on and overtopping an impermeable seawall. Comparison with free-surface profiles and laboratory images shows that GPUSPH satisfactorily reproduces the complicated wave processes involving wave plunging, collapsing, splash-up, and overtopping. The other set of experiments investigates tsunamilike solitary wave breaking and inundation over shallow water reefs. The performance of GPUSPH is evaluated by comparing its results with (1) experimental data including free-surface measurements and cross-shore velocity profiles, and (2) published numerical results obtained in two mesh-based wave models: the nonhydrostatic wave model CCHE2D and the Boussinesq-type wave model FUNWAVE. The capability of GPUSPH to simulate nonlinear wave phenomena, such as wave shoaling, reflection, and refraction, is confirmed by comparing the wave field predicted by CCHE2D. Although all three models correctly simulate the solitary wave propagation offshore and the bore due to the broken wave run-up nearshore, GPUSPH outperforms CCHE2D and FUNWAVE in terms of resolving wave plunging and collapsing. The conducted two case studies show that the meshless SPH method is reliable for predicting tsunami breaking in the nearshore zone.
85 1 - PublicationRestrictedSpectral properties of the SPH Laplacian operatorIn order to address the question of the SPH (Smoothed Particle Hydrodynamics) Laplacian conditioning, a spectral analysis of this discrete operator is performed. In the case of periodic Cartesian particle network, the eigenfunctions and eigenvalues of the SPH Laplacian are found on theoretical grounds. The theory agrees well with numerical eigenvalues. The effects of particle disorder and non-periodicity conditions are then investigated from numerical viewpoint. It is found that the matrix condition number is proportional to the square of the particle number per unit length, irrespective of the space dimension and kernel choice.
45 1 - PublicationRestrictedHOTSAT: a multiplatform system for the thermal monitoring of volcanic activity using satellite data(2015-10-29)
; ; ; ; ; ;Ganci, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Bilotta, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Cappello, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Herault, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Del Negro, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; ; ; ; The HOTSAT multiplatform system for the analysis of infrared data from satellites provides a framework that allows the detection of volcanic hotspots and an output of their associated radiative power. This multiplatform system can operate on both Moderate Resolution Imaging spectroradiometer and Spinning Enhanced Visible and Infrared Imager data. The new version of the system is now implemented on graphics processing units and its interface is available on the internet under restricted access conditions. Combining the estimation of time-varying discharge rates using HOTSAT with the MAGFLOW physics-based model to simulate lava flow paths resulted in the first operational system in which satellite observations drive the modelling of lava flow emplacement. This allows the timely definition of the parameters and maps essential for hazard assessment, including the propagation time of lava flows and the maximum run-out distance. The system was first used in an operational context during the paroxysmal episode at Mt Etna on 12–13 January 2011, when we produced real-time predictions of the areas likely to be inundated by lava flows while the eruption was still ongoing. This allowed key at-risk areas to be rapidly and appropriately identified.163 34 - PublicationRestrictedMAGFLOW: a physics-based model for the dynamics of lava-flow emplacement(2015-07-30)
; ; ; ; ; ;Cappello, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Herault, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Bilotta, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Ganci, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Del Negro, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; ; ; ; The MAGFLOW model for lava-flow simulations is based on the cellular automaton (CA) approach, and uses a physical model for the thermal and rheological evolution of the flowing lava. We discuss the potential of MAGFLOW to improve our understanding of the dynamics of lava-flow emplacement and our ability to assess lava-flow hazards. Sensitivity analysis of the input parameters controlling the evolution function of the automaton demonstrates that water content and solidus temperatures are the parameters to which MAGFLOW is most sensitive. Additional tests also indicate that temporal changes in effusion rate strongly influence the accuracy of the predictive modelling of lava-flow paths. The parallel implementation of MAGFLOW on graphic processing units (GPUs) can achieve speed-ups of two orders of magnitude relative to the corresponding serial implementation, providing a lava-flow simulation spanning several days of eruption in just a few minutes. We describe and demonstrate the operation of MAGFLOW using two case studies from Mt Etna: one is a reconstruction of the detailed chronology of the lava-flow emplacement during the 2006 flank eruption; and the other is the production of the lava-flow hazard map of the persistent eruptive activity at the summit craters.190 35