# Workshop ASTROFLU IV

## Motivations and objectives

the first two local events ‘ASTROFLU’ were principally organised by the Henri Bénard PC in Lyon, 12-13/11/2008 and 15/12/2011. The third one, which took place on November 20-21, 2013, attracted an European audience and was supported by ERCOFTAC with label and sholarships.

The aim of our new ASTROFLU IV workshop is to once again gather the fluid mechanics specialists from the physics, engineering, astrophysics, and mathematics communities in order to exchange ideas and collaborate on our common interests.

The main theme of our first event was pulsating stars, because of the shared interest on highly compressible flows, theory, computation and modelling, and with particular emphasis on shock / turbulence interactions. The second theme on rotating shear flows was addressed in ASTROFLU II. There is a strong parallel between (rotating) accretion discs in the astrophysical applications, and rotating shear flows in geophysics (ocean, atmosphere), and in engineering (turbomachinery). The tools we use are often very similar, but we use multiple terminologies, and, crucially, tend to publish in separate journals. To give an example, the use of the shearing sheet approximation in astrophysics is also very similar to the pseudo-spectral DNS (Orszag / Patterson) using coordinates comoving with the mean shear (from Rogallo 1982), with now the ‘snoopy’ code from Geoffroy Lesur (Grenoble) used in the astrophysical community. There is a large scientific network of astrophysicists engaged in the study of rotating accretion disks, possibly including the effects of stratification and MHD. In the last event ASTROFLU III, a large emphasis was also given to studies in geophysics, from the Earth to rapidly rotating giant planets.

We hope that ASTROFLU IV will mark a new orientation, with:

- Emphasis on plasmas physics, both in astrophysics / heliophysics and in engineering, as the studies for controlled nuclear fusion by electromagnetic confinment (ITER).
- To explore the analogy between radiation of acoustic waves and the very recent theory of gravitational wave turbulence, from aeroacoustics in Engineering to cosmology.

# Program

## January, the 23rd

- 10 h 00 - 10 h 30 Opening
- 10 h 30 - 11 h 10
*On gravitational wave turbulence*, Sébastien Galtier (Polytechnique and Université Paris sud) - 11 h 10 - 11 h 30
*re-creation (récréation !): Art and cosmology*, Marie Christine Cambon - 11 h 30 - 12 h 00
*Inertial wave turbulence in a shearless channel*, Julian Scott (LMFA, with Alexandr Eremin, Fabien S. Godeferd and Anne Cadiou) - 12 h 00 - 12 h 30
*Noise radiated from localized — or not! — vortical sources*, Christophe Bailly (LMFA, with Philippe Blanc-Benon and Claude Cambon) - 12 h 30 - 14 h 00 Lunch
- 14 h 00 - 14 h 30
*Subcritical turbulent condensate in rapidly rotating Rayleigh-Bénard convection*, Benjamin Favier (IRPHE, Marseille) - 14 h 30 - 15 h 00 Round Table on wave turbulence
- 15 h 00 - 16 h 30
*Magnetic self-organisation in protoplanetary discs*, by Geoffroy Lesur (Grenoble) - 16 h 30 - 17 h 00
*On compressible MHD*, Thierry Lehner (LUTH, Paris- Meudon) - 17 h 00 - 17 h 30
*On eddies in the ocean*, Philippe Fraunié (Toulon)

## January, the 24th

- 10 h 00 - 10 h 30
*Numerical methods for the multi-fluid plasma equations for space and laboratory plasmas*, Alejandro Alvarez Laguna (LPP Polytechnique, near Paris) - 10 h 30 - 11 h 00
*Turbulence and transport in edge plasmas for magnetic confinement fusion*, Eric Serre (M2P2, Marseille) - 11 h 00 - 11 h30
*Fluid mechanics of the RFP fusion plasma*, by Wouter Bos (LMFA) - 11 h 30 - 12 h 30 Round table on plasma physics, to be included in a new ‘geoastro’ SIG to be launched (Raffaele Marino)
- 12 h 30 - 13 h 00
*TBA*, Susan Kurien (LANL, Los Alamos, USA) - 13 h 00 - 14 h 30 Lunch
- 14 h 30 - 15 h 00
*Shallow water magnetohydrodynamics in astrophysical fluid dynamics*, Arakel Petrosyan (IKI, Russian Federation) - 15 h 00 - 15 h 30
*Buoyancy-driven flows from constant to periodic acceleration*, Antoine Briard (CMLA and CEA, near Paris) - 15 h 30 - 16 h 00
*On protoplanetary discs*, Héloı̈se Méheut (Observatoire de Nice) - 16 h 00 - 16 h 30
*Exchanges of energy in rotating MHD*, Aziz Salhi - 16 h 30 - 17 h 00
*Simulations of turbulent rotating flows using the PITM method*by Bruno Chaouat (ONERA, near Paris) - 17 h 00 - 17 h 30
*TBA*, Freddy Bouchet and Mickaël Bourgoin (ENS Lyon)