Public thesis defense of Alexandre Puyguiraud in the Montpellier University

We communicate that Alexandre Puyguiraud defends his PhD Thesis on 25th April in the Montpellier University

Title: "Upscaling Transport in Heterogeneous Media: from Pore to Darcy scale through Continuous Time Random Walks"
PhD Thesis: Alexandre Puyguiraud
Location: Conference Room of the IEM building - Montpellier University
300 Avenue du Professeur Emile Jeanbrau, 34090 Montpellier, France
Date: Wednesday, 25th April 2019 – 2:15 pm


The responsible mechanisms for anomalous (non-Fickian) hydrodynamic transport can be traced back to the complexity of the medium geometry at the pore-scale. In this thesis, we investigate the dynamics of pore-scale particle velocities. Using particle tracking simulations performed on a digitized Berea sandstone sample, we present a detailed analysis of the evolution of the Lagrangian and Eulerian evolution and their dependence on the initial conditions. The particles experience a complex intermittent temporal velocity signal along their streamline while their spatial velocity series exhibit regular fluctuations. The spatial velocity distribution of the particles converges quickly to the steady-state. These results lead naturally to Markov processes for the prediction of these velocity series.

These processes, together with the tortuosity and the velocity correlation distance that are properties of the medium, allow the parameterization of a continuous time random walk (CTRW) for the upscaling of the transport. The model, like any upscaled model, relies on the definition of a representative elementary volume (REV). We show that an REV based on the velocity statistics allows defining a pertinent support for modeling pre-asymptotic to asymptotic hydrodynamic transport at Darcy scale using, for instance, CTRW, thus overcoming the limitations associated with the Fickian advection dispersion equation. Finally, we investigate the impact of pore-scale heterogeneity on a bimolecular reaction and explore a methodology for the prediction of the mixing volume and the chemical mass produced.

Composition of the Jury:

  • Dr Alberto GUADAGNINI Professor, Politecnico di Milano
  • Dr Philippe ACKERER Head of Research, University of Strasbourg
  • Dr Séverin PISTRE Professor, CNRS, University of Montpellier
  • Dr Michel QUINTARD Head of Research, Institute of Fluid Mechanics of Toulouse
  • Dr Insa NEUWEILER Professor, University of Hannover
  • Dr Markus HOLZNER Professor, ETH Zürich
  • Dr Philippe GOUZE Head of Research, CNRS, University of Montpellier
  • Dr Marco DENTZ Professor, Spanich National Research Council (IDAEA-CSIC), Barcelona


Alexandre Puyguiraud Thesi


 Announcement in the Montpellier University


Miércoles, 24 de Abril de 2019