Computational astrophysics has rapidly developed in the recent years, enabling, since only recently, multi-scale, multi-physics simulations of entire stars, planets, galaxies, and cosmic explosions (see e.g. Mueller 2004). The main goal of the proposed workshop is to address several physical processes and computational methods which are common to the study of very different astrophysical problems. The main concerned fields are (i) multi-dimensional stellar structure and evolution, (ii) planetary atmospheric circulation, and (iii) explosive fate of stars. The common ground of these ields are multi-scale, magneto-hydrodynamical flows and turbulence in different facets. And all the topics are interdisciplinary with strong connections between different research areas. The research on all these fields is currently very active and fashionable, characterized by important investment from the national and international communities devoted to both observational (ground- and space- based instruments) and computational developments (developments of large computer facilities, such as IDRIS on the French national level, or PRACE on an European scale).

Within the past decade, computer facilities and development of computational methods have literally exploded, allowing huge progress in our understanding of star and planet formation, a complex field which combines radiative- and magneto-hydrodynamics, the physics of shocks, supersonic turbulence and elaborated computational methods such as adaptive mesh refinement techniques (see e.g Chabrier et al. 2007).  Also, recent numerical development devoted to the study of multi-dimensional hydrodynamical processes, such as turbulent convection, rotation, magnetic field and dynamo generation, mixing processes, now allows a better understanding of stellar structures through the development of new generations of multi-dimensional stellar models(Deaborn et al. 2006; Browning 2008; Mocak et al. 2009).

With the discovery of extrasolar planets, new laboratories for the physics of planet atmosphere has been found, opening new avenues for the understanding of atmospheric circulation and climatology, not only on Earth but also on these new worlds (Showman et al. 2008). This field is now extremely active and represents nowadays a perfect example of interdisciplinarity, requiring complementary expertises from fluid dynamics, radiative transfer, planetology, climatology and the development of sophisticated numerical simulations.

Cosmic explosion are driving the chemical evolution of the universe. There are two basic mechanism for this. The first one is based on nuclear detonation fronts in the degenerate matter of white dwarfs. The main computational problem here is to combine the flame scale with the global convection scale. To treat the flame propagation, different numerical techniques are applied, from direct numerical simulations (Zingale et al. 2005) to level set methods (Röpke, Woosley, & Hillebrandt 2007). The second mechanism is based on neutrino driven explosions of massive stars, requiring complex radiative transfer calculations on the basis of Boltzmann equations for photons (Janka et al. 2005) and a good treatment of the magnetic dynamo driven by the magnetic-rotational instability (Obergaulinger et al. 2006). A subclass of this process has a connection to Gamma-Ray-Bursts.

Turbulence is one of the physical processes present in all fields. Cosmic turbulence is is often highly compressible and even supersonic (e.g.  Kritsuket al. 2007). Turbulence models are starting to be developed for these environments (Schmidt et al 2006). While astrophysics can profit from the waste experience of engineering and fundamental physics, space provides an excellent laboratory for those regimes of turbulence not present on Earth.

The organizers have recognized expertises in different fields covered by the topics of the workshop, namely stellar physics and evolution (Chabrier & Baraffe 2000; Baraffe et al. 1998), star and planet formation (Chabrier et al. 2007), multi-dimensional simulations and computational astrophysics (Walder & Folini 2000; Walder et al. 2008) and code development (Walder & Folini 1999).