References of "Besseron, Xavier 50000761"
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See detailBuffer XDEM
Mainassara Chekaraou, Abdoul Wahid UL; Besseron, Xavier UL; Rousset, Alban UL et al

Scientific Conference (in press)

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See detailProcess analysis in thermal process engineering with high-performance computing using the example of grate firing
Peters, Bernhard UL; Rousset, Alban UL; Besseron, Xavier UL et al

in Process analysis in thermal process engineering with high- performance computing using the example of grate firing (in press)

Biomass as a renewable energy source continues to grow in popularity to reduce fossil fuel consumption for environmental and economic benefits. In the present contribution, the combustion chamber of a 16 ... [more ▼]

Biomass as a renewable energy source continues to grow in popularity to reduce fossil fuel consumption for environmental and economic benefits. In the present contribution, the combustion chamber of a 16 MW geothermal steam super-heater, which is part of the Enel Green Power "Cornia 2" power plant, is being investigated with high-performance computing methods. For this purpose, the extended discrete element method (XDEM) developed at the University of Luxembourg is used in a high-performance computing environment, which includes both the moving wooden bed and the combustion chamber above it. The XDEM simulation platform is based on a hybrid four-way coupling between the Discrete Element Method (DEM) and Computational Fluid Dynamics (CFD). In this approach, particles are treated as discrete elements that are coupled by heat, mass, and momentum transfer to the surrounding gas as a continuous phase. For individual wood particles, besides the equations of motion, the differential conservation equations for mass, heat, and momentum are solved, which describe the thermodynamic state during thermal conversion. The consistency of the numerical results with the actual system performance is discussed in this paper to determine the potentials and limitations of the approach. [less ▲]

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See detail6-way coupling of DEM+CFD+FEM with preCICE
Besseron, Xavier UL; Rousset, Alban UL; Peyraut, Alice et al

Presentation (2020, February)

In this work, we present our preliminary results on the 6-way coupling of 3 numerical solvers: XDEM for the Discrete Element Method (DEM), OpenFOAM for Computation Fluid Dynamics (CFD), and deal.II for ... [more ▼]

In this work, we present our preliminary results on the 6-way coupling of 3 numerical solvers: XDEM for the Discrete Element Method (DEM), OpenFOAM for Computation Fluid Dynamics (CFD), and deal.II for Finite Element Method (FEM). We relied on the existing preCICE adapters for OpenFOAM and deal.II and we have implemented a new preCICE adapter for the eXtended Discrete Element Method (XDEM), an innovative DEM software developed at the University of Luxembourg. The XDEM adapter permits coupling of the particulate phase of DEM with CFD and FEM: - DEM+FEM is a surface coupling that performs the exchange of surface forces and displacement between the particles and a deformable solid; - DEM+CFD is a volume coupling that performs the exchange of porosity, momentum, drag force and buoyancy between the particles and the fluid. Put together with the pre-existing CFD+FEM coupling, we obtain a 6-way coupled multi-physics solver for particles, fluid and deformable solids. We have tested and evaluated our multi-physics solver on the tutorial case “Cylinder with a flap” derived from the benchmarking case of Turek and Hron, that we extended to include a particulate phase solved by XDEM. [less ▲]

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See detailHigh Performance Parallel Coupling of OpenFOAM+XDEM
Besseron, Xavier UL; Pozzetti, Gabriele; Rousset, Alban UL et al

Presentation (2019, June 21)

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See detailShort Introduction to the Roofline Model
Besseron, Xavier UL

Presentation (2019, June 20)

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See detailA parallel dual-grid multiscale approach to CFD-DEM couplings
Pozzetti, Gabriele UL; Jasak, Hrvoje; Besseron, Xavier UL et al

in Journal of Computational Physics (2019), 378

In this work, a new parallel dual-grid multiscale approach for CFD-DEM couplings is investigated. Dual- grid multiscale CFD-DEM couplings have been recently developed and successfully adopted in different ... [more ▼]

In this work, a new parallel dual-grid multiscale approach for CFD-DEM couplings is investigated. Dual- grid multiscale CFD-DEM couplings have been recently developed and successfully adopted in different applications still, an efficient parallelization for such a numerical method represents an open issue. Despite its ability to provide grid convergent solutions and more accurate results than standard CFD-DEM couplings, this young numerical method requires good parallel performances in order to be applied to large-scale problems and, therefore, extend its range of application. The parallelization strategy here proposed aims to take advantage of the enhanced complexity of a dual-grid coupling to gain more flexibility in the domain partitioning while keeping a low inter-process communication cost. In particular, it allows avoiding inter- process communication between CFD and DEM software and still allows adopting complex partitioning strategies thanks to an optimized grid-based communication. It is shown how the parallelized multiscale coupling holds all its natural advantages over a mono-scale coupling and can also have better parallel performance. Three benchmark cases are presented to assess the accuracy and performance of the strategy. It is shown how the proposed method allows maintaining good parallel performance when operated over 1000 processes. [less ▲]

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See detailSecurity, reliability and regulation compliance in Ultrascale Computing System
Bouvry, Pascal UL; Varrette, Sébastien UL; Wasim, Muhammad Umer UL et al

in Zomaya, A. Y.; Carretero, J.; Jeannot, E. (Eds.) Ultrascale Computing Systems (2019)

Ultrascale Computing Systems (UCSs) are envisioned as large-scale complex systems joining parallel and distributed computing systems that will be two to three orders of magnitude larger than today’s ... [more ▼]

Ultrascale Computing Systems (UCSs) are envisioned as large-scale complex systems joining parallel and distributed computing systems that will be two to three orders of magnitude larger than today’s systems (considering the number of Central Process Unit (CPU) cores). It is very challenging to find sustainable solutions for UCSs due to their scale and a wide range of possible applications and involved technologies. For example, we need to deal with heterogeneity and cross fertilization among HPC, large-scale distributed systems, and big data management. One of the challenges regarding sustainable UCSs is resilience. Another one, which attracted less interest in the literature but becomes more and more crucial with the expected convergence with the Cloud computing paradigm, is the notion of regulation in such system to assess the Quality of Service (QoS) and Service Level Agreement (SLA) proposed for the use of these platforms. This chapter covers both aspects through the reproduction of two articles: [1] and [2]. [less ▲]

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See detailThe XDEM Multi-physics and Multi-scale Simulation Technology: Review on DEM-CFD Coupling, Methodology and Engineering Applications
Peters, Bernhard UL; Baniasadi, Maryam UL; Baniasadi, Mehdi UL et al

in Particuology (2019), 44

The XDEM multi-physics and multi-scale simulation platform roots in the Ex- tended Discrete Element Method (XDEM) and is being developed at the In- stitute of Computational Engineering at the University ... [more ▼]

The XDEM multi-physics and multi-scale simulation platform roots in the Ex- tended Discrete Element Method (XDEM) and is being developed at the In- stitute of Computational Engineering at the University of Luxembourg. The platform is an advanced multi- physics simulation technology that combines flexibility and versatility to establish the next generation of multi-physics and multi-scale simulation tools. For this purpose the simulation framework relies on coupling various predictive tools based on both an Eulerian and Lagrangian approach. Eulerian approaches represent the wide field of continuum models while the Lagrange approach is perfectly suited to characterise discrete phases. Thus, continuum models include classical simulation tools such as Computa- tional Fluid Dynamics (CFD) or Finite Element Analysis (FEA) while an ex- tended configuration of the classical Discrete Element Method (DEM) addresses the discrete e.g. particulate phase. Apart from predicting the trajectories of individual particles, XDEM extends the application to estimating the thermo- dynamic state of each particle by advanced and optimised algorithms. The thermodynamic state may include temperature and species distributions due to chemical reaction and external heat sources. Hence, coupling these extended features with either CFD or FEA opens up a wide range of applications as diverse as pharmaceutical industry e.g. drug production, agriculture food and processing industry, mining, construction and agricultural machinery, metals manufacturing, energy production and systems biology. [less ▲]

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See detailVerlet buffer for broad phase interaction detection in Discrete Element Method
Mainassara Chekaraou, Abdoul Wahid UL; Rousset, Alban UL; Besseron, Xavier UL et al

Poster (2018, September 24)

The Extended Discrete Element Method (XDEM) is a novel and innovative numerical simulation technique that extends the dynamics of granular materials or particles as described through the classical ... [more ▼]

The Extended Discrete Element Method (XDEM) is a novel and innovative numerical simulation technique that extends the dynamics of granular materials or particles as described through the classical discrete element method (DEM) by additional properties such as the thermodynamic state, stress/strain for each particle. Such DEM simulations used by industries to set up their experimental processes are complexes and heavy in computation time. Therefore, simulations have to be precise, efficient and fast in order to be able to process hundreds of millions of particles. To tackle this issue, such DEM simulations are usually parallelized with MPI. One of the most expensive computation parts of a DEM simulation is the collision detection of particles. It is classically divided into two steps: the broad phase and the narrow phase. The broad phase uses simplified bounding volumes to perform an approximated but fast collision detection. It returns a list of particle pairs that could interact. The narrow phase is applied to the result of the broad phase and returns the exact list of colliding particles. The goal of this research is to apply a Verlet buffer method to (X)DEM simulations regardless of which broad phase algorithm is used. We rely on the fact that such DEM simulations are temporal coherent: the neighborhood only changes slightly from the last time-step to the current time-step. We use the Verlet buffer method to extend the list of pairs returned by the broad phase by stretching the particles bounding volume with an extension range. This allows re-using the result of the broad phase for several time-steps before an update is required once again and thereby its reduce the number of times the broad phase is executed. We have implemented a condition based on particles displacements to ensure the validity of the broad phase: a new one is executed to update the list of colliding particles only when necessary. This guarantees identical results because approximations introduced in the broad phase by our approach are corrected in the narrow phase which is executed at every time-steps anyway. We perform an extensive study to evaluate the influence of the Verlet extension range on the performance of the execution in terms of computation time and memory consumption. We consider different test-cases, partitioners (ORB, Zoltan, METIS, SCOTCH, ...), broad phase algorithms (Link cell, Sweep and prune, ...) and grid configurations (fine, coarse), sequential and parallel (up to 280 cores). While a larger Verlet buffer increases the cost of the broad phase and narrow phase, it also allows skipping a significant number of broad phase execution (> 99 \%). As a consequence, our first results show that this approach can speeds up the total .execution time up to a factor of 5 for sequential executions, and up to a factor of 3 parallel executions on 280 cores while maintaining a reasonable memory consumption. [less ▲]

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See detailA co-located partitions strategy for parallel CFD-DEM couplings
Pozzetti, Gabriele UL; Besseron, Xavier UL; Rousset, Alban UL et al

in Advanced Powder Technology (2018)

In this work, a new partition-collocation strategy for the parallel execution of CFD–DEM couplings is investigated. Having a good parallel performance is a key issue for an Eulerian-Lagrangian software ... [more ▼]

In this work, a new partition-collocation strategy for the parallel execution of CFD–DEM couplings is investigated. Having a good parallel performance is a key issue for an Eulerian-Lagrangian software that aims to be applied to solve industrially significant problems, as the computational cost of these couplings is one of their main drawback. The approach presented here consists in co-locating the overlapping parts of the simulation domain of each software on the same MPI process, in order to reduce the cost of the data exchanges. It is shown how this strategy allows reducing memory consumption and inter-process communication between CFD and DEM to a minimum and therefore to overcome an important parallelization bottleneck identified in the literature. Three benchmarks are proposed to assess the consistency and scalability of this approach. A coupled execution on 280 cores shows that less than 0.1% of the time is used to perform inter-physics data exchange. [less ▲]

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See detailHybrid MPI+OpenMP Implementation of eXtended Discrete Element Method
Mainassara Chekaraou, Abdoul Wahid UL; Rousset, Alban UL; Besseron, Xavier UL et al

in Proc. of the 9th Workshop on Applications for Multi-Core Architectures (WAMCA'18), part of 30th Intl. Symp. on Computer Architecture and High Performance Computing (SBAC-PAD 2018) (2018, September)

The Extended Discrete Element Method (XDEM) is a novel and innovative numerical simulation technique that ex- tends classical Discrete Element Method (DEM) (which simulates the motion of granular material ... [more ▼]

The Extended Discrete Element Method (XDEM) is a novel and innovative numerical simulation technique that ex- tends classical Discrete Element Method (DEM) (which simulates the motion of granular material), by additional properties such as the chemical composition, thermodynamic state, stress/strain for each particle. It has been applied successfully to numerous industries involving the processing of granular materials such as sand, rock, wood or coke [16], [17]. In this context, computational simulation with (X)DEM has become a more and more essential tool for researchers and scientific engineers to set up and explore their experimental processes. However, increasing the size or the accuracy of a model requires the use of High Performance Computing (HPC) platforms over a parallelized implementation to accommodate the growing needs in terms of memory and computation time. In practice, such a parallelization is traditionally obtained using either MPI (distributed memory computing), OpenMP (shared memory computing) or hybrid approaches combining both of them. In this paper, we present the results of our effort to implement an OpenMP version of XDEM allowing hybrid MPI+OpenMP simulations (XDEM being already parallelized with MPI). Far from the basic OpenMP paradigm and recommendations (which simply summarizes by decorating the main computation loops with a set of OpenMP pragma), the OpenMP parallelization of XDEM required a fundamental code re-factoring and careful tuning in order to reach good performance. There are two main reasons for those difficulties. Firstly, XDEM is a legacy code devel- oped for more than 10 years, initially focused on accuracy rather than performance. Secondly, the particles in a DEM simulation are highly dynamic: they can be added, deleted and interaction relations can change at any timestep of the simulation. Thus this article details the multiple layers of optimization applied, such as a deep data structure profiling and reorganization, the usage of fast multithreaded memory allocators and of advanced process/thread-to-core pinning techniques. Experimental results evaluate the benefit of each optimization individually and validate the implementation using a real-world application executed on the HPC platform of the University of Luxembourg. Finally, we present our Hybrid MPI+OpenMP results with a 15%-20% performance gain and how it overcomes scalability limits (by increasing the number of compute cores without dropping of performances) of XDEM-based pure MPI simulations. [less ▲]

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See detailParallel Coupling of CFD-DEM simulations
Besseron, Xavier UL; Pozzetti, Gabriele UL; Rousset, Alban UL et al

Presentation (2018, August 20)

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See detailParallel Coupling of CFD-DEM simulations
Pozzetti, Gabriele UL; Besseron, Xavier UL; Rousset, Alban UL et al

Presentation (2018, August)

Eulerian-Lagrangian couplings are nowadays widely used to address engineering and technical problems. In particular, CFD-DEM couplings have been successfully applied to study several configurations ... [more ▼]

Eulerian-Lagrangian couplings are nowadays widely used to address engineering and technical problems. In particular, CFD-DEM couplings have been successfully applied to study several configurations ranging from mechanical, to chemical and environmental engineering. However, such simulations are normally very computationally intensive, and the execution time represents a major issue for the applicability of this numerical approach to complex scenarios. With this work, we introduce a novel coupling approach aiming at improving the performance of the parallel CFD-DEM simulations. This strategy relies on two points. First, we propose a new partition-collocation strategy for the parallel execution of CFD–DEM couplings, which can considerably reduce the amount of inter-process communication between the CFD and DEM parts. However, this strategy imposes some alignment constraints on the CFD mesh. Secondly, we adopt a dual-grid multiscale scheme for the CFD-DEM coupling, that is known to offer better numerical properties, and that allows us to obtain more flexibility on the domain partitioning overcoming the alignment constraints. We assess the correctness and performance of our approach on elementary benchmarks and at a large scale with a realistic test-case. The results show a significant performance improvement compared to other state-of-art CFD-DEM couplings presented in the literature. [less ▲]

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See detailHigh Performance Computing and Big Data analytics in Luxembourg: Overview and Challenges in the EuroHPC horizon
Besseron, Xavier UL; Varrette, Sébastien UL

Presentation (2018, August)

Accelerating modelling and simulation in the data deluge era requires the appropriate hardware and infrastructure at scale. The University of Luxembourg is active since 2007 to develop its own ... [more ▼]

Accelerating modelling and simulation in the data deluge era requires the appropriate hardware and infrastructure at scale. The University of Luxembourg is active since 2007 to develop its own infrastructure and expertise in the HPC and BD domains. The current state of developments will be briefly reviewed in the context of the national and European HPC strategy in which Luxembourg is starting to play a role. [less ▲]

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See detailHydrodynamic Analysis of Gas-Liquid-Liquid-Solid Reactors using the XDEM Numerical Approach
Baniasadi, Maryam UL; Peters, Bernhard UL; Baniasadi, Mehdi UL et al

in Canadian Journal of Chemical Engineering (2018)

Multiphase reactors are abundantly used in many industries. Among them, few reactors deal with four phases called gas-liquid-liquid-solid systems, which received less attention due to their complex ... [more ▼]

Multiphase reactors are abundantly used in many industries. Among them, few reactors deal with four phases called gas-liquid-liquid-solid systems, which received less attention due to their complex situation. Numerical study of such complex systems is not easy and requires loads of computational effort. In this study, a discrete-continuous numerical model known as eXtended discrete element method (XDEM) is proposed to investigate the hydrodynamic behaviour of fluid phases passing through the packed bed of solid particles. This model is applied to the dripping zone of a blast furnace. In this zone, two distinct liquid phases, namely liquid iron and slag, flow through a pile of coke particles while exchanging momentum. In this work, besides the solid-fluid and gas-liquid interactions, the liquid-liquid interactions are also studied and the phases' mutual effects are discussed. In addition, a sensitivity study on the slag viscosity is performed, which shows the importance of liquid phase properties on the system behaviour. The results evaluation shows that the liquid iron accelerates the downward flow of the slag and the slag decelerates the downward flow of the liquid iron phase due to the resistance force caused by their relative velocity. [less ▲]

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See detailA Parallel Multiscale DEM-VOF Method For Large-Scale Simulations Of Three-Phase Flows
Pozzetti, Gabriele UL; Besseron, Xavier UL; Rousset, Alban UL et al

in Proceedings of ECCM-ECFD 2018 (2018)

A parallel dual-grid multiscale DEM-VOF coupling is here investigated. Dual- grid multiscale couplings have been recently used to address different engineering problems involving the interaction between ... [more ▼]

A parallel dual-grid multiscale DEM-VOF coupling is here investigated. Dual- grid multiscale couplings have been recently used to address different engineering problems involving the interaction between granular phases and complex fluid flows. Nevertheless, previous studies did not focus on the parallel performance of such a coupling and were, therefore, limited to relatively small applications. In this contribution, we propose an insight into the performance of the dual-grid multiscale DEM-VOF method for three- phase flows when operated in parallel. In particular,we focus on a famous benchmark case for three-phase flows and assess the influence of the partitioning algorithm on the scalability of the dual-grid algorithm. [less ▲]

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See detailRapidRMSD: Rapid determination of RMSDs corresponding to motions of flexible molecules
Neveu, Emilie; Popov, Petr; Hoffmann, Alexandre et al

in Bioinformatics (2018)

Detailed reference viewed: 136 (20 UL)