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LNCMI > Magneto-science > Magnetohydrodynamics

Magnetohydrodynamics

Description
Staff
Techniques
Publications

Description

Magnetohydrodynamics (MHD) studies the behavior of electrically conductive fluids in the presence of electromagnetic fields.

At the LNCMI both MHD of liquid metal and MHD of transparent media allowing direct optical observations, are developped. It permits to address various key questions including the one of turbulence under the influence of magnetic fields. Turbulence lies at the heart of an large variety of natural and industrial processes. Turbulence leads flows to exhibit intense, erratic fluctuations over a wide range of length scales, making them extremely difficult to predict. Our limited understanding of their dynamics limits the development of computationally effective models and impedes progress in some of the greatest challenges in physics and engineering: how does the motion of liquid iron in the Earth core sustain the Earth’s B ? What is the optimal design for liquid metal heat exchangers to efficiently extract heat from nuclear fusion or upcoming sodium/molten salts fast reactors ?
These challenges demand a profound understanding of how turbulence is affected by the Lorentz force, which arises within conducting fluids pervaded by a B.

Research staff

Dist of main collaborators :

  • Alban Potherat, Professor at Coventry University
  • Suzanne Horn, Professor at Coventry University
  • Samy Lalloz, assistant Professor at Coventry University (former Cotutelle PhD from 2021 to 2024)
  • Laurent Davoust, Professor at Grenoble-INP
  • Jürgen Spitznagel, Engineer at LNCMI
  • Martin Holdsworth, Engineer at Coventry University

Techniques

The LNCMI high field MHD activity is based on a ten year scientific collaboration gathering the Fluid Mechanics group at Coventry University (Prof. A. Potherat & Prof. S. Horn), the MHD group at SIMAP-G-INP (Prof. L. Davoust) and the LNCMI (Dr F. Debray, J. Spitznagel).

The FLOWCUBE Experiment

The FLOWCUBE experiments is using liquid metal and focus on studies on turbulence and the specific magneto-waves the so-called Alfven Waves. In this experiment mapping of the flow are reconstructed from voltage measurements at the wall combined, when necessary, with ultrasonic probing.

The FLOWCUBE Experiment for 2D/3D turbulence, Alfven waves

J X B drive a turbulent InGaSn  flow diagnosed

  • with electrical probes at the boundaries
  • with ultrasound velocimetry along B.

Main contributors :

Prof. A. Pothérat & S. Lalloz (Coventry Univ)
Prof. L. Davoust (SIMAP Grenoble-INP)
F. Debray & J. Spitznagel  (LNCMI)

The LEE experiments

The Little Earth Experiment (LEE) uses a transparent conductive media and aims at modeling the complex magneto-convection which occurs in the earth (and planetary) inner core.

One crucial issue for the development  of such a science is the avaibility of high magnetic  fields in large volumes  in order to observe the phenomena on a wide range of lengthscales to permit spectral analysis. LNCMI-Grenoble is today the only place worldwide where magnetic fields in excess of 10 teslas is made available to researchers in large bore configuration (in excess of 350 mm of diameter).

The LEE Experiments for Magnetoconvection in the Earth core

A half sphere filled with  acid  is rotating inside the magnet PIV is used to obtain the velocity field

Main contributors :

Prof. A. Pothérat, Prof . S. Horn, D. Keogh, M. Holdsworth (Coventry Univ)

F. Debray, J. Spitznagel, R. Pankow (LNCMI)

Publications

Selected publications

Four  key publications:

Alfvén waves at low magnetic Reynolds number: transitions between diffusion, dispersive Alfvén waves and nonlinear propagation. Journal of Fluid Mechanics, 2025, 1003, pp.A19.

⟨10.1017/jfm.2024.1165⟩. ⟨hal-04909131⟩

 

Magnetic Taylor-Proudman Constraint Explains Flows into the Tangent Cylinder. Physical Review Letters, 2024,

⟨10.1103/PhysRevLett.133.184101?_gl=1*1qah8v5*_ga*MTU1NDM3MTY1Ni4xNzI3NzcyNzIx*_ga_ZS5V2B2DR1*MTczOTQ0MTc3Ni43LjEuMTczOTQ0MTkwNy4wLjAuOTk2OTA5NjEz⟩. ⟨hal-04945388⟩

Inverse and Direct Energy Cascades in Three-Dimensional Magnetohydrodynamic Turbulence at Low Magnetic Reynolds Number. Physical Review Letters, 2018, 120 (22), ⟨10.1103/PhysRevLett.120.224502⟩. ⟨hal-01897904⟩

 

Experimental evidence of Alfvén wave propagation in a Gallium alloy. Physics of Fluids, 2011, 23 (9),

pp.096601. ⟨10.1063/1.3633090⟩. ⟨hal-00602640v2⟩