Subgrid modelling of Rayleigh-Taylor and Richtmyer-Meshkov instabilities in astrophysical contexts

• Applicant: Professor Marcus Brüggen, Ph.D.
• Subject Area: Astrophysics and Astronomy
• Term: from 2009 to 2013
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 97993990

The Rayleigh-Taylor (RT) instability occurs when a fluid of density pH is accelerated or supported against gravity by a fluid of lower density pL. It affects phenomena from inertial confinement fusion to supernova explosions in the regime of large Reynolds number (Re). The Richtmyer-Meshkov (RM) instability occurs when a shock encounters a discontinuity in acoustic impedance such as at a density step. Today s three-dimensional numerical simulations can fully resolve these instabilities for Re ~104, at least as long as the flow involves simple hydrodynamics. However, many astrophysical flows have very large Reynolds numbers (> 106) and the simulations cannot properly resolve the hydrodynamical instabilities. In many cases, the instabilities become nonlinear and produce turbulence. Examples for such flows include the turbulent flames in type la Supernovae and the evolution of AGN-blown cavities in galaxy clusters. Such flows evolve self-similarly with an eddy length scale that grows in proportion to the width of the mixing region. Then, subgrid or turbulence models are necessary to describe the evolution of the flow. This is an issue that is routinely neglected in astrophysical applications but, yet, crucially important. We propose to implement and test a state-of-the-art subgrid model into an adaptive-mesh code and apply it to astrophysical settings. The code developed in the framework of this proposal will be made public to the community.

• DFG Programme: Research Grants
• Participating Person: Professor Dr. Stephan Rosswog