Geophysical complex systems

Particles, flows and patterns

Cyril Gadal

Institut de Mécanique des Fluides de Toulouse (IMFT), France

General background

  • CPGE Physics/Chemistry
  • License of Physics, major Geosciences
  • Master of Geosciences, major Geophysical Fluid Dynamics
  • Master of Physics, major Fluid Dynamics and Soft Matter

PhD thesis: Sand dunes

(IPGP, 2017 – 2020)

Dunes gathering at the bottom of a small mountain in the Taklamacan desert, in China.

PostDoc: Turbidity currents

(IMFT, 2021 – 2023)

Powder snow avalanche at the Zinal ski station, in Switzerland. (@Zacharie Grossen)

General background

PostDoc: Riverbed clogging

(IMFT, 2023 – 2024)

Underwater view of the River Tara riverbed, in Montenegro. (@LiquiArt)

PostDoc: Cohesive granular flows

(Manchester, starting 2024)

Dense snow avalanche at the Grand-Bornand ski station, in France.

From a hydrodynamic instability to dune patterns shaping sand seas

Dunes gathering at the bottom of a small mountain in the Taklamacan desert, in China.

supervised by Clément Narteau (IPGP) and Philippe Claudin (PMMH)

Dunes – General questions

  • Inference/constraints, where measurements are not possible or available (winds, grain size)
  • Risks, land management in arid, coastal areas

Dune patterns on Mars. (@NASA)

Dune moving over a road, Egypt. (@Yann Arthus-Bertrand)

→ Need for a quantitative understanding of dune morphodynamics, in real conditions

Dunes – Focus of my PhD

  • Multidirectional wind regimes
  • Boundary conditions

Emergence and instabilities

Theory, Experiments, Numerical simulations, Field data

Mature and non-linear patterns

Numerical simulations, Field data

Large scale mecanisms

Theory, Field data

Turbidity currents: lock-release and steady influx systems

Powder snow avalanche at the Zinal ski station, in Switzerland. (@Zacharie Grossen)

in collaboration with Matthieu Mercier (IMFT) and Laurent Lacaze (IMFT)

Turbidity currents – General questions

  • Natural hazards, risks
  • Geological constraints, inference from deposits

Pyroclastic flow, Sinabung, Indonesia (@Jean-Guillaume Feignon)

Turbidity current deposit (Wilkin et al. 2023)
  • Fundamental questions:
    • particle/something (turbulence, wall) interactions
    • entrainment in particle-laden flows

Turbidity currents – Focus of my work

  • Influence of particle buoyancy
  • Influence of bottom slope

Lock-release turbidity current

Experiments

Steady influx turbidity current

Experiments

Depth-averaged models

Theory

Particle flow in porous media: the example of riverbed clogging

Underwater view of the River Tara riverbed, in Montenegro. (@LiquiArt)

in collaboration with Matthieu Mercier (IMFT) and Laurent Lacaze (IMFT)

Riverbed clogging – General questions

  • Risks, Land managment: flood, impacts of dam presence
  • Ecosystem preservation: life, transfer across the riverbed (pollution, nutrients)

Photograph of the Sanmenxia Dam during silt flushing. (@RolfMueller)

Salmon eggs buried in riverbed gravels. (@Olympic National Park)
  • Fundamental questions:
    • clogging and unclogging (if possible ?) thresholds
    • spatio-temporal dynamics
    • particle dynanimcs inside the porous media

Riverbed clogging – Focus of my work

  • Spatio-temporal dynamics of the percolation
  • Clogging and unclogging (if possible ?) thresholds

Development of flume experiments

Experiments

Associated Metrology

Ultrasound velocity measurements

Quantitative measurements within the hydrogel bead matrix

Work in progress …

Self-organization in cohesive granular flows

in collaboration with Nico Gray (Manchester) and Chris Johnson (Manchester)

  • Prediction (risk, natural hazards, efficiency in industrial contexts)

→ Need for fast models, validated on experiments

Example: Self-channelization of a cohesive granular avalanche

Miscalleneous

Other current research projects:

  • Impacts in viscoplastic fluids (J. Neufeld and S. Dalziel, DAMTP, Cambridge)
  • Reaction-diffusion patterns in LCTEM experiments (IPGP, Paris – LMSC, Paris)

Other interests:

  • Open science, FAIR principles
  • helping in developping/maintaining some Python libs (matplotlib, lmfit)