Comptes Rendus Physique

Michael Le Bars

Stephan Fauve

Comptes Rendus
Physique
Michael Le Bars and Stephan Fauve
Foreword to the special issue: Geophysical and astrophysical fluid dynamics in the
laboratory
Volume 25, Special Issue S3 (2024), p. 1-4
Online since: 6 June 2025
Part of Special Issue: Geophysical and astrophysical fluid dynamics in the laboratory
Guest editors: Stephan Fauve (Laboratoire de Physique de l’ENS, CNRS, PSL Research
University, Sorbonne Université, Université Paris Cité, Paris, France) and Michael Le
Bars (CNRS, Aix Marseille Univ, Centrale Marseille, IRPHE, Marseille, France)
https://doi.org/10.5802/crphys.253
This article is licensed under the
Creative Commons Attribution 4.0 International License.
http://creativecommons.org/licenses/by/4.0/
C EN T R E
MER S ENN E
The Comptes Rendus. Physique are a member of the
Mersenne Center for open scientific publishing
www.centre-mersenne.org — e-ISSN : 1878-1535
Comptes Rendus. Physique
2024, Vol. 25, Special issue S3, p. 1-4
https://doi.org/10.5802/crphys.253
Foreword / Avant-propos
Geophysical and astrophysical fluid dynamics in the laboratory /
Dynamique des fluides géophysiques et astrophysiques au
laboratoire
Foreword to the special issue: Geophysical
and astrophysical fluid dynamics in the
laboratory
Avant-propos du numéro spécial : Dynamique des
fluides géophysiques et astrophysiques au laboratoire
Michael Le Bars ,∗,a and Stephan Fauve ,b
a CNRS, Aix Marseille Univ, Centrale Marseille, IRPHE, Marseille, France
b Laboratoire de Physique de l’École Normale Supérieure, ENS, Université PSL, CNRS,
Sorbonne Université, Université de Paris, 75005 Paris, France
E-mails: michael.le-bars@cnrs.fr (M. Le Bars), stephan.fauve@phys.ens.fr (S. Fauve)
Abstract. This special issue brings together 19 review articles addressing a broad range of problems in
geophysical and astrophysical fluid dynamics, reflecting both the current state of the art and ongoing
research, with a special focus on the contribution of laboratory experiments. This foreword outlines the
general context and key challenges of the field, and places the individual contributions in perspective.
Résumé. Ce numéro spécial réunit 19 articles de revue couvrant un large spectre de problématiques en
dynamique des fluides géophysiques et astrophysiques, reflétant à la fois l’état de l’art et les recherches
en cours, avec un accent particulier sur l’apport des expériences en laboratoire. Cette préface présente le
contexte général et les principaux défis du domaine, et met en perspective les différentes contributions.
Keywords. Geophysical fluid dynamics, Astrophysical fluid dynamics, Laboratory experiments.
Mots-clés. Dynamique des fluides géophysiques, Dynamique des fluides astrophysiques, Expériences de
laboratoire.
Manuscript received and accepted 20 May 2025.
1. Introduction
Geophysical and Astrophysical Fluid Dynamics (GAFD) encompasses all types of flows occurring
in any natural system, from Earth’s atmosphere and oceans to the interiors of planets and stars,
and even toastrophysical structures such as accretion disks. These systems involve a wide
∗Corresponding author
ISSN (electronic): 1878-1535 https://comptes-rendus.academie-sciences.fr/physique/
2 Michael Le Bars and Stephan Fauve
range of fluids—air, water, liquid metals, plasmas—and span extensive spatial and temporal
scales. Despite this diversity, GAFD research is unified by a common set of governing equations
and a shared methodological framework: the construction of simplified models that isolate
fundamental physical mechanisms. This special issue explores how laboratory experiments
contribute to advancing our understanding of these generic mechanisms.
GAFD often involves extreme flow regimes and complex coupled physics that challenge nu-
merical and theoretical approaches. While computational tools have advanced rapidly, particu-
larly with the emergence of data-driven techniques, laboratory experiments remain indispens-
able. They give direct access to real systems, inherently including all physical effects, bound-
ary conditions, and spatial and temporal scales, without relying on parameterizations or clo-
sure models. Laboratory experiments allow systematic exploration of parameter space and sus-
tained operation in extreme regimes, thereby yielding statistically converged data. Laboratory
flows emerge directly from the fundamental equations with no a priori, and can thus reveal
rare, serendipitous and unexpected behaviors. These strengths coexist with inherent drawbacks:
quantitative measurements are always challenging and limited, and experiments are constrained
by practical restrictions on e.g. geometry, scale separation, and working fluid properties.
2. Topics overview
This special issue provides an overview of the state of the art and ongoing research in experi-
mental GAFD. The 19 review articles highlight the breadth of physical processes accessible in the
lab and underline the universality of the mechanisms across planetary and astrophysical con-
texts. The contributions demonstrate that progress stems from both large-scale experimental
platforms and small-scale analog models.
Convection is a classical and long-standing research topic in fluid mechanics, with particular
features in GAFD. Natural systems are often expected to operate in so-called ultimate regimes,
where diffusive effects become negligible. While the existence of such a regime remains a subject
of debate in the context of Rayleigh–Bénard convection, a radiatively driven convection setup
has recently demonstrated an ultimate regime in a novel configuration [1]. Rotation plays a
dominant role in GAFD, and its influence on convection has been studied experimentally for
over seventy years, remaining a very active area of research [2]. Furthermore, many natural
systems—including oceans, gas giants, and stellar interiors—feature multiple buoyancy sources,
leading to complex double-diffusive convection regimes that are especially prone to laboratory
investigation [3].
Phase-change dynamics are fundamental across planetary layers but remain challenging
to parameterize due to complex interactions between fluid mechanics and out-of-equilibrium
thermodynamics. Laboratory investigations address phenomena ranging from planetary surface
ablation [4] to core crystallization processes [5]. The resulting solid boundary topographies,
spanning multiple scales, increase the complexity of GAFD flows and offer a valuable platform
for controlled experimental studies [6].
Multiphase flows pose major challenges for numerical modeling and are ubiquitous in natural
systems. Experimental studies target applications ranging from marine plastic transport [7] and
dune morphodynamics [8] to soil erosion [9] and metal-silicate differentiation during planetary
accretion [10].
Stratification and rotation are fundamental components of GAFD, driving instabilities such as
baroclinic modes [11]. They govern complex flow regimes including jet dynamics [12] and mixing
in stratified turbulence [13]. They also sustain internal waves—gravity and inertial, respectively—
that share many characteristics but exhibit key differences [14]. Internal waves play a central
role in geophysical and astrophysical dynamics, particularly through their nonlinear interactions
Michael Le Bars and Stephan Fauve 3
that sustain wave turbulence [15] and generate mean flow oscillations, exemplified by the quasi-
biennial oscillation [16].
Magnetohydrodynamics (MHD) is a central component of GAFD, yet remains particularly
challenging to investigate experimentally. Ambitious laboratory setups, often pushing the lim-
its of current technology, have been developed to explore MHD phenomena. The dynamics of
accretion disks has been a subject of intense experimental effort [17]. Dynamo action remains
a long-standing goal, with several past attempts yielding limited success. Nonetheless, notable
progress includes the laboratory-scale observation of magnetic field reversals [18]. New experi-
mental platforms are now entering the arena offering new opportunities for exploration [19].
3. Conclusion
This special issue is intended for researchers in GAFD, scientists from adjacent disciplines,
and early-career or prospective students. It also aims to foster dialogue across traditionally
compartmentalized fields—including atmospheric sciences, oceanography, deep geophysics,
planetology, astrophysics, fluid mechanics, and nonlinear physics. Finally, it highlights the role
of experimental GAFD as a powerful tool for education and outreach, thanks to accessible and
illustrative setups that make complex processes tangible for students and the broader public.
In conclusion, laboratory experiments remain a cornerstone of GAFD. They complement
observations, theory, and numerical simulations, providing unique access to physical insight.
This role is increasingly critical as we seek to understand the changing dynamics of our planet
and the surprising behaviors emerging from newly explored planetary and stellar systems.
References
[1] G. Hadjerci, V. Bouillaut, B. Miquel, S. Aumaître and B. Gallet, “Radiatively driven convection: diffusivity-free
regimes of geophysical and astrophysical flows in the laboratory”, C. R. Phys. 25 (2024), no. S3, pp. 5–20.
[2] A. Pothérat and S. Horn, “Seven decades of exploring planetary interiors with rotating convection experiments”,
C. R. Phys. 25 (2024), no. S3, pp. 21–75.
[3] A. Tilgner, “Experiments on double diffusive convection”, C. R. Phys. 25 (2024), no. S3, pp. 77–94.
[4] S. Carpy, M. Berhanu, M. Chaigne and S. C. du Pont, “Fingerprints of surface flows on solid substrates ablated by
phase change: from laboratory experiments to planetary landscapes”, C. R. Phys. 25 (2024), no. S3, pp. 95–142.
[5] L. Huguet, Q. Kriaa, T. Alboussière and M. L. Bars, “Solid–liquid phase change in planetary cores”, C. R. Phys. 25
(2024), no. S3, pp. 143–181.
[6] J. Vidal, J. Noir, D. Cébron, F. Burmann, R. Monville, V. Giraud and Y. Charles, “Geophysical flows over topography,
a playground for laboratory experiments”, C. R. Phys. 25 (2024), no. S3, pp. 183–234.
[7] M. Poulain-Zarcos, N. Pujara, G. Verhille and M. J. Mercier, “Laboratory experiments related to marine plastic
pollution: a review of past work and future directions”, C. R. Phys. 25 (2024), no. S3, pp. 235–266.
[8] P. Claudin, S. C. du Pont and C. Narteau, “From lab to landscape-scale experiments for the morphodynamics of
sand dunes”, C. R. Phys. 25 (2024), no. S3, pp. 267–295.
[9] P. Philippe and N. Benahmed, “Quantifying soil surface erosion”, C. R. Phys. 25 (2024), no. S3, pp. 297–332.
[10] R. Deguen, L. Huguet, M. Landeau, V. Lherm, A. Maller and J.-B. Wacheul, “Fluid dynamics of planetary differen-
tiation”, C. R. Phys. 25 (2024), no. S3, pp. 333–377.
[11] U. Harlander, M. V. Kurgansky, K. Speer and M. Vincze, “Baroclinic instability from an experimental perspective”,
C. R. Phys. 25 (2024), no. S3, pp. 379–426.
[12] P. Read, Y. Afanasyev, J. Aurnou and D. Lemasquerier, “Eddy-driven zonal jet flows in the laboratory”, C. R. Phys.
25 (2024), no. S3, pp. 427–477.
[13] A. Lefauve, “Geophysical stratified turbulence and mixing in the laboratory”, C. R. Phys. 25 (2024), no. S3, pp. 479–
507.
[14] S. Joubaud, S. Boury and P. Odier, “Internal gravity waves versus inertial waves in the laboratory”, C. R. Phys. 25
(2024), no. S3, pp. 509–535.
[15] P.-P. Cortet and N. Lanchon, “Turbulence of internal gravity waves in the laboratory”, C. R. Phys. 25 (2024), no. S3,
pp. 537–556.
4 Michael Le Bars and Stephan Fauve
[16] B. Semin and F. Pétrelis, “Quasi-biennial oscillation: laboratory experiments”, C. R. Phys. 25 (2024), no. S3, pp. 557–
581.
[17] C. Gissinger, “Laboratory modeling of MHD accretion disks”, C. R. Phys. 25 (2024), no. S3, pp. 583–610.
[18] F. Pétrélis, “Experimental dynamos: from models to applications to the geodynamo”, C. R. Phys. 25 (2024), no. S3,
pp. 611–627.
[19] F. Stefani, S. Anders, S. Eckert, et al., “The DRESDYN precession experiment”, C. R. Phys. 25 (2024), no. S3, pp. 629–
647.


Foreword to the special issue: Geophysical and astrophysical fluid dynamics in the laboratory

Alban Pothérat

Susanne Horn

Seven decades of exploring planetary interiors with rotating convection experiments

Pierre Philippe

Nadia Benahmed

Quantifying soil surface erosion

Christophe Gissinger

Laboratory modeling of MHD accretion disks

Karyn Le Hur

Sariah Al Saati

Quantum Hall and Light Responses in a 2D Topological Semimetal

Marc Gabay

Topological phases driven by orbital entanglement in Transition Metal Oxide Perovskite interfaces

Marie Poulain-Zarcos

Nimish Pujara

Gautier Verhille

Matthieu J. Mercier

Laboratory experiments related to marine plastic pollution: a review of past work and future directions

Benoît Semin

François Pétrelis

Quasi-biennial oscillation: laboratory experiments

Félix Werner

Xavier Leyronas

Three-body contact for fermions.  I. General relations

Emmanuelle Conil

François Costa

Lionel Pichon

Comptes Rendus
Physique
Emmanuelle Conil, François Costa and Lionel Pichon
Energy in the heart of EM waves: modelling, measurements and
management—Foreword
Volume 25, Special Issue S1 (2024), p. 1-3
Online since: 23 October 2024
Issue date: 19 December 2024
Part of Special Issue: Energy in the heart of EM waves: modelling, measurements and
management
Guest editors: Emmanuelle Conil (ANFR, France), François Costa (ENS Paris-Saclay,
Université Paris-Saclay, Université Paris-Est Créteil, France) and Lionel Pichon (CNRS,
CentraleSupélec, Université Paris-Saclay, Sorbonne Université, France)
https://doi.org/10.5802/crphys.209
This article is licensed under the
Creative Commons Attribution 4.0 International License.
http://creativecommons.org/licenses/by/4.0/
C EN T R E
MER S ENN E
The Comptes Rendus. Physique are a member of the
Mersenne Center for open scientific publishing
www.centre-mersenne.org — e-ISSN : 1878-1535
Comptes Rendus. Physique
2024, Vol. 25, Special issue S1, p. 1-3
https://doi.org/10.5802/crphys.209
Energy in the heart of EM waves: modelling, measurements and
management / L’énergie au cœur des ondes électromagnétiques :
modélisation, mesures et gestion
Energy in the heart of EM waves: modelling,
measurements and management—Foreword
L’énergie au cœur des ondes électromagnétiques :
modélisation, mesures et gestion — Avant-propos
Emmanuelle Conil ,a, François Costa ,b and Lionel Pichon ,∗,c
a Agence nationale des fréquences, ANFR, Maisons-Alfort, France
b ENS Paris-Saclay, Université Paris-Saclay, Université Paris-Est Créteil, France
c CNRS, CentraleSupélec, Université Paris-Saclay, Sorbonne Université, France
E-mail: Lionel.Pichon@centralesupelec.fr (L. Pichon)
Energy is more relevant than ever: modes of transmission, harvesting, conversion, storage as
well as associated materials and systems are interdisciplinary issues in many sectors of activity
(mobility, communication, etc.). Electromagnetic waves play an increasing role in the transmis-
sion, control and management of energy, both through fundamental aspects, technological de-
velopments and analysis tools.
Electromagnetics engineering related to waves involves appropriate numerical modeling and
simulation tools for analysis and design. Experimental protocols are simultaneously required to
measure electromagnetic fields according to energy levels, frequencies, etc., particularly in case
of human exposure considerations and biomedical engineering. Also, management strategies
including virtual prototyping and electromagnetic compatibility analysis (EMC) are currently
widely adopted in the design of electrical and electronic systems over a wide range of frequencies
from DC to hundreds of GHz.
The URSI-France 2023 workshop, organized under the auspices of the French Academy of Sci-
ences, focused on “Energy in the heart of waves”. It was jointly organized by SATIE (Information
and Energy Technology, Systems and Applications) and GeePs (Group of electrical engineering—
Paris). The workshop was held on the campus of CentraleSupélec, in Gif-sur-Yvette (France),
from March 21 to March 22, 2023.
The following special issue is organized in 9 papers covering different aspects and challenges
related to electromagnetic waves including: modelling, measurement and management.
∗Corresponding author
ISSN (electronic): 1878-1535 https://comptes-rendus.academie-sciences.fr/physique/
2 Emmanuelle Conil et al.
This special issue is introduced by an invited “review paper” from Prof. Stavros Koulouridis
(University of Patras) dealing with wireless power transfer in biomedical engineering. It presents
an analysis of implantable antenna systems using the scattering matrices formalism.
Electromagnetic fields interact with living matter driving an exhaustive research related to hu-
man exposure. A first group of four papers is related to public exposure to electromagnetic waves
including in-situ measurement techniques and dedicated simulation tools. These contributions
cover both public area in case of radio-communications systems (5G for example) and industrial
workplaces in case of electromagnetic fields radiated by power systems (in the kHz range).
The first paper entitled “A Simulation Method Suited for the Whole French Territory Electro-
magnetic Waves Exposure” and authored by Nicolas Noé, Lydia Sefsouf, Jean-Benoit Dufour,
Samuel Carré, Emmanuelle Conil, Nabila Bounoua and Jean-Benoit Agnani presents a dedicated
simulation method for the numerical modeling of the whole French territory’s exposure to Elec-
tromagnetic fields. The method accounts for EMF exposure everywhere (outdoors and inside
buildings), while performing fast enough to fulfill operational constraints.
The second paper entitled “Monitoring of the exposure to electromagnetic fields with au-
tonomous probes installed outdoors in France” is authored by Ourouk Jawad, Emmanuelle Conil,
Jean-Benoît Agnani, Shanshan Wang and Joe Wiart. It draws statistical conclusions on the expo-
sure of the population based on temporal analysis of exposure monitored by autonomous broad-
band probes. It shows that monitoring probes are able to detect the seasonality of the exposure
and provide analysis of correlation between monitoring probes and radio environment.
The third paper entitled “Extensive 5G measurement campaign to monitor EMF exposure in
France” is authored by Lydia Sefsouf, Emmanuelle Conil and Jean-Benoît Agnani. It focuses on
the exposure evolution related to the deployment of 5G on the French national territory during
the year 2021. More than 5000 measurements were part of a large exposure monitoring program
at nearly 2000 sites.
The fourth paper entitled “Electromagnetic compatibility of active cardiovascular implants to
occupational magnetic field environments: impact of the field direction” is authored by Lucien
Hammen, Lionel Pichon, Yann Le Bihan, Mohamed Bensetti and Gérard Fleury. It presents a
new testing method to assess the electromagnetic compatibility method of active implantable
medical devices against occupational magnetic field sources. It is based on an experimental
approach using a specific test bench able to generate a controlled magnetic field in all space
directions up to the high occupational exposure limits between 50 Hz and 3 kHz.
Appropriate 3D modeling approaches and computational methods are required to understand
the interaction between electromagnetic fields and the environment and also to design and op-
timize complex structures. A second group of four papers shows dedicated numerical methods
and simulation tools for investigations in realistic environments.
The fifth paper entitled “3D Computation of Lightning Leader Stepped Propagation Inside a
Realistic Cloud” is authored by Philippe Dessante. It studies the propagation of leaders in clouds
or toward the ground and structures. It describes a modeling approach involving a macro model
and a heuristic based on the electric potential’s maximization to find a leader’s direction in case
of a real cloud space charge repartition.
The sixth paper entitled “Multi-label classification with deep learning techniques applied to
the B-Scan images of GPR” is authored by Soukayna El Karakhi, Alain Reineix and Christophe
Guiffaut. It is related to object detection with ground penetrating radar. It presents a multi-
label classification model based on transfer learning and data augmentation dedicated to B-scan
images.
The seventh paper entitled “Design and optimization of inductive power transfer systems by
metamodeling techniques” is authored by Yao Pei, Lionel Pichon, Mohamed Bensetti and Yann Le
Bihan. It addresses wireless power transfer for charging batteries of electric vehicles. It presents
Emmanuelle Conil et al. 3
a fast design and optimization methodology of a power transfer systems based of metamodeling
techniques.
The eighth paper entitled “Matching of an observed event and its virtual model in relation to
smart theories, coupled models and supervision of complex procedures—A review” is authored by
Adel Razek. It aims to illustrate the nature of the observation–modeling (or real–virtual) link, the
importance of the exact model in the matching involved in this link and the use of this link in the
supervision of complex procedures via the digital twin concept.
We believe that this Special Issue will provide readers with a valuable opportunity to have an
overview of the challenges and progress in the field of electromagnetics and waves. We hope that
all contents of this Special Issue demonstrate useful and insightful knowledge to the community.
First, we thank the authors who decided to submit their work and contribute to this Special
Issue. Second, we are indebted with anonymous expert reviewers, who devoted considerable
time and efforts in the review of the submitted manuscripts, providing always valuable feedback
to the authors. Finally, we would like to thank the scientific committee of the URSI-France
2023 workshop for its contribution to the development of the program and the Comptes Rendus
Physique editorial committee for agreeing to publish this special issue.


Energy in the heart of EM waves: modelling, measurements and management—Foreword

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