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Uncertainties

UQ at CERFACS

The activity on uncertainty quantification at CERFACS aims to estimate uncertainties in computational models requiring large computational resources.  We consider applications related to environmental risk, data assimilation and optimization in a high performance computing context.

The principal actions are:

  • Ensemble experimental design for calibration of uncertain model parameters
  • Development cost-effective Surrogate Model methodologies for computationally intensive problems
  • Sensitivity analysis, optimization and data assimilation
  • Development of efficient algorithms for stochastic parameter estimation

These actions are implemented for the following applications:

  • Surrogates for high dimensional problems in hydraulics and aerodynamics.
  • Efficient, scalable and resilient domain decomposition algorithms for exascale computing
  • Surrogate models for large-eddy simulations of pollution dispersion in the atmospheric boundary layer
  • Developing Multifidelity-MLMC algorithms for industrial CFD, multidisciplinary systems and geosciences.
  • Building simple climate models to explore data constraints on climate projections

Context

Models are approximations of systems.  Confidence in model simulations requires an understanding of their uncertainties.

Uncertainties are generally classified according to their nature. There are several sources of error:

  • errors related to simplifications of equations (dimensional reduction, empirical parameterization)
  • errors related to the numerical schemes
  • errors related to spatio-temporal discretization.

Models must be supplemented by data and parameters that describe the system, initial conditions and its boundary conditions. The physical parameters govern the  laws of the system – and sometimes, these data and parameters are only partially and approximately observed and known.

Errors can be further classified into two groups :

  • Epistemic errors linked to a lack of knowledge of system processes
  • Random errors linked to the stochastic nature of the system

Our aim is to understand and quantify the extent to which epistemic and random uncertainties affect the model response.  At CERFACS, we develop a suite of tools to better understand this propagation of uncertainty.

  • Multi-fidelity Monte-Carlo methods to allow the efficient estimation of probabilistic parameter distributions for industrial and geoscience applications
  • Novel surrogate models to allow rapid exploration of parameter response in global climate and CFD problems.
  • Risk assessment tools bridging scales for climate impacts, connecting global uncertainties to local impacts.

 

At CERFACS, these activity are transversal, with applications ranging from flood forecasting to wildland fire propagation, climate projection uncertainty and combustion chamber ignition models.

Partners

  • EDF
  • IRT
  • ONERA
  • LIMSI
  • CMAP
  • Inria
  • AIRBUS
  • SAFRAN

NEWS

CERFACS Combustion paper on rocket engines selected as Distinguished Paper at the last Int. Symp. on Comb. in Adelaide

superadmin |  14 April 2021

The paper of C. Laurent 'Heat-release dynamics in a doubly- transcritical LO2/LCH4 cryogenic coaxial jet flame subjected to fuel inflow acoustic modulation’  has been selected at the Distinguished Paper in the Gas Turbine and Rocket Engine Combustion colloquium for the 38th International Symposium on Combustion. This paper authored by Laurent, Staffelbach, Nicoud  and  T. Poinsot  is available here:  describes the first LES of a forced doubly transcritical flame.Read more


New Cerfacs’ Activity Report available

superadmin |  25 March 2021

The Cerfacs activity report covering the period from January 2019 to December 2020 is available.Read more

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