Documents published in Scipedia

• D5.3 Report on theoretical work to allow the use of MLMC with adaptive mesh refinement

  Q. Ayoul-Guilmard, S. Ganesh, M. Nuñez, R. Tosi, F. Nobile, R. Rossi, C. Soriano

  Open Access Repository of the ExaQUte project: Deliverables (2021). 10

  
  

  Abstract

  This documents describes several studies undertaken to assess the applicability of MultiLevel Monte Carlo (MLMC) methods to problems of interest; namely in turbulent fluid flow over civil engineering structures. Several numerical experiments are presented wherein the convergence of quantities of interest with mesh parameters are studied at different Reynolds’ numbers and geometries. It was found that MLMC methods could be used successfully for low Reynolds’ number flows when combined with appropriate Adaptive Mesh Refinement (AMR) strategies. However, the hypotheses for optimal MLMC performance were found to not be satisfied at higher turbulent Reynolds’ numbers despite the use of AMR strategies. Recommendations are made for future research directions based on these studies. A tentative outline for an MLMC algorithm with adapted meshes is made, as well as recommendations for alternatives to MLMC methods for cases where the underlying assumptions for optimal MLMC performance are not satisfied. 

  Abstract
  This documents describes several studies undertaken to assess the applicability of MultiLevel Monte Carlo (MLMC) methods to problems of interest; namely in turbulent fluid [...]

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• D6.4 Report on stochastic optimisation for unsteady problems

  Q. Ayoul-Guilmard, F. Nobile, S. Ganesh, M. Nuñez, A. Kodakkal, R. Rossi, C. Soriano

  Open Access Repository of the ExaQUte project: Deliverables (2021). 9

  
  

  Abstract

  This report brings together methodological research on stochastic optimisation and work on benchmark and target applications of the ExaQute project, with a focus on unsteady problems. A practical, general method for the optimisation of the conditional value at risk is proposed. Three different optimisation problems are described: an oscillator problem selected as a suitable trial and illustration case; the shape optimisation of an airfoil, chosen as a benchmark application in the project; the shape optimisation of a tall building, which is the challenging target application set for ExaQUte. For each problem, the current developments and results are presented, the application of the proposed method is discussed, and the work to be done until the end of the project is laid out. 

  Abstract
  This report brings together methodological research on stochastic optimisation and work on benchmark and target applications of the ExaQute project, with a focus on unsteady [...]

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• D3.2 Report on parallel in time methods and release of the solvers

  M. Caicedo, J. Principe, R. Codina, R. Rossi, C. Soriano

  Open Access Repository of the ExaQUte project: Deliverables (2021). 8

  
  

  Abstract

  In this deliverable we provide the details related to the design, implementation, and scalability analysis of Space Time Balancing Domain Decomposition by Constraints (STBDDC) preconditioners that have been implemented in the FEMPAR project [8]. First, we describe the state of the art of space-time methods in Sect. 2 and we then provide some details of our particular implementation in Sect. 3. Next, in Sect. 4, we present a detailed description of the numerical experiments performed during the project showing the excellent scalability results that these algorithms permit to achieve. At the same time, we show the limitations of these algorithms when dealing with nonlinear problems. Finally we draw some concluding remarks in Sect. 5. 

  Abstract
  In this deliverable we provide the details related to the design, implementation, and scalability analysis of Space Time Balancing Domain Decomposition by Constraints (STBDDC) [...]

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• D5.4 Report on MLMC for time dependent problems

  Q. Ayoul-Guilmard, S. Ganesh, M. Nuñez, R. Tosi, F. Nobile, R. Rossi, C. Soriano

  Open Access Repository of the ExaQUte project: Deliverables (2021). 7

  
  

  Abstract

  In this report, we study the use of Multi-Level Monte Carlo (MLMC) methods for time dependent problems. It was found that the usability of MLMC methods depends strongly on whether or not the underlying time dependent problem is chaotic in nature. Numerical experiments are conducted on both simple problems, as well as fluid flow problems of practical interest to the ExaQUte project, to demonstrate this. For the non-chaotic cases, the hypotheses that enable the use of MLMC methods were found to be satisfied. For the chaotic cases, especially the case of high Reynolds’ number fluid flow, the hypotheses were not satisfied. However, it was found that correlations between the different levels were high enough to merit the use of multi-fidelity or control-variate approaches. It was also noted that MLMC methods could work for chaotic problems if the time window of analysis were chosen to be small enough. Future studies are proposed to examine this possibility.

  Abstract
  In this report, we study the use of Multi-Level Monte Carlo (MLMC) methods for time dependent problems. It was found that the usability of MLMC methods depends strongly on [...]

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• D7.2 Finalization of "deterministic" verification and validation tests

  A. Apostolatos, R. Rossi, C. Soriano

  Open Access Repository of the ExaQUte project: Deliverables (2021). 6

  
  

  Abstract

  This deliverable focus on the verification and validation of the solvers of Kratos Multiphysics which are used within ExaQUte. These solvers comprise standard body-fitted approaches and novel embedded approaches for the Computational Fluid Dynamics (CFD) simulations carried out within ExaQUte. Firstly, the standard body-fitted CFD solver is validated on a benchmark problem of high rise building - CAARC benchmark and subsequently the novel embedded CFD solver is verified against the solution of the body-fitted solver. Especially for the novel embedded approach, a workflow is presented on which the exact parameterized Computer-Aided Design (CAD) model is used in an efficient manner for the underlying CFD simulations. It includes: A note on the space-time methods Verification results for the body-fitted solver based on the CAARC benchmark Workflow consisting of importing an exact CAD model, tessellating it and performing embedded CFD on it Verification results for the embedded solver based on a high-rise building API definition and usage 

  Abstract
  This deliverable focus on the verification and validation of the solvers of Kratos Multiphysics which are used within ExaQUte. These solvers comprise standard body-fitted [...]

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• D1.3 First public Release of the solver

  R. Badia, J. Ejarque, F. Nobile, M. Nuñez, C. Soriano, C. Roig, R. Rossi, R. Tosi

  Open Access Repository of the ExaQUte project: Deliverables (2021). 5

  
  

  Abstract

  This deliverable presents the software release of Kratos Multiphysics, together with the XMC library, Hyperloom and PyCOMPSs API definition [8]. This report is meant to serve as a supplement to the public release of the software. Kratos is “a framework for building parallel, multi-disciplinary simulation software, aiming at modularity, extensibility, and high performance. Kratos is written in C++, and counts with an extensive Python interface”. XMC is a python library for hierarchical Monte Carlo algorithms. Hyperloom and PyCOMPSs are environments for enabling parallel and distributed computation. 

  Abstract
  This deliverable presents the software release of Kratos Multiphysics, together with the XMC library, Hyperloom and PyCOMPSs API definition [8]. This report is meant to serve [...]

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• D1.1 Solvers "stub" implementation of the capabilities to be delivered

  R. Rossi, I. López, C. Soriano

  Open Access Repository of the ExaQUte project: Deliverables (2021). 4

  
  

  Abstract

  The current deliverable describes the initial API available for the solvers. The API is intended to be based on the Kratos Multiphysics fraemework and will evolve during the project. The current deliverable describes the essential features of the interface and provides an initial working implementation to be used as a basis for the future developements. The initial implementation described here is currently operative on the master branch of Kratos. As of the end of July 2018 (moment of handing in of current deliverable) the interface is operative and is being used “in production”. Nevertheless, it still does not fully support the model serialization capabilities that are needed for pyCompSS and HyperLoom. The interface is documented in the project wiki page [wiki]. The same documentation is also presented in the current deliverable.

  Abstract
  The current deliverable describes the initial API available for the solvers. The API is intended to be based on the Kratos Multiphysics fraemework and will evolve during the [...]

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• D1.4 Final public Release of the solver

  F. Nobile, R. Badia, J. Ejarque, L. Cirrottola, A. Froehly, B. Keith, A. Kodakkal, M. Nuñez, C. Roig, R. Tosi, R. Rossi, C. Soriano

  Open Access Repository of the ExaQUte project: Deliverables (2021). 3

  
  

  Abstract

  This deliverable presents the final software release of Kratos Multiphysics, together with the XMC library, Hyperloom and PyCOMPSs API definitions [13]. This release also contains the latest developements on MPI parallel remeshing in ParMmg. This report is meant to serve as a supplement to the public release of the software. Kratos is “a framework for building parallel, multi-disciplinary simulation software, aiming at modularity, extensibility, and high performance. Kratos is written in C++, and counts with an extensive Python interface”. XMC is “a Python library for parallel, adaptive, hierarchical Monte Carlo algorithms, aiming at reliability, modularity, extensibility and high performance“. Hyperloom and PyCOMPSs are environments for enabling parallel and distributed computation. ParMmg is an open source software which offers the parallel mesh adaptation of three dimensional volume meshes.

  Abstract
  This deliverable presents the final software release of Kratos Multiphysics, together with the XMC library, Hyperloom and PyCOMPSs API definitions [13]. This release also [...]

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• D2.2 First release of the octree mesh-generation capabilities and of the parallel mesh adaptation kernel

  A. Martín, L. Cirrottola, A. Froehly, R. Rossi, C. Soriano

  Open Access Repository of the ExaQUte project: Deliverables (2021). 2

  
  

  Abstract

  This document presents a description of the octree mesh-generation capabilities and of the parallel mesh adaptation kernel. As it is discussed in Section 1.3.2 of part B of the project proposal there are two parallel research lines aimed at developing scalable adaptive mesh refinement (AMR) algorithms and implementations. The first one is based on using octree-based mesh generation and adaptation for the whole simulation in combination with unfitted finite element methods (FEMs) and the use of algebraic constraints to deal with non-conformity of spaces. On the other hand the second strategy is based on the use of an initial octree mesh that, after make it conforming through the addition of templatebased tetrahedral refinements, is adapted anisotropically during the calculation. Regarding the first strategy the following items are included: Description of the octree-based AMR kernel with space-filling curves. Description of a outer, wrapping AMR layer supporting FEM needs. Numerical results in a distributed environment. Regarding the second strategy the following items are included: An outline of the anisotropic mesh adaptation algorithm. A description of the state of the art of the implementation. A discussion on the ongoing and future work.

  Abstract
  This document presents a description of the octree mesh-generation capabilities and of the parallel mesh adaptation kernel. As it is discussed in Section 1.3.2 of part B of [...]

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• D1.2 First realease of the softwares

  R. Tosi, R. Amela, M. Nuñez, C. Roig, R. Badia, R. Rossi, C. Soriano

  Open Access Repository of the ExaQUte project: Deliverables (2021). 1

  
  

  Abstract

  This deliverable presents the software release of the Kratos Multiphysics software [3], ”a framework for building parallel, multi-disciplinary simulation software, aiming at modularity, extensibility, and high performance. Kratos is written in C++, and counts with an extensive Python interface”. In this deliverable we focus on the development of Uncertainty Quantification inside Kratos. This takes place in the MultilevelMonteCarloApplication, a recent development inside the software that allows to deal with uncertainty quantification.

  Abstract
  This deliverable presents the software release of the Kratos Multiphysics software [3], ”a framework for building parallel, multi-disciplinary simulation software, aiming [...]

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