Modelling turbulence in astrophysical fluids

Abstract

Turbulent flows are widespread in nature, appearing on length scales going from smoke emanating from incense sticks to plasma in intergalactic medium, and play a critical role in mixing, transport, and the creation of structures. Despite its significance, turbulent behaviour in classical physics remains largely an unanswered question. In recent years, tremendous progress has been made in our understanding of the complex physics of turbulence through the use of computer simulation. Here, we integrate a module that induces turbulence into the PLUTO code for Astrophysical gas dynamics, which is a piece of software that is available for free distribution, has a structure that is both modular and adaptable, and is capable of running on anywhere from a single CPU to several thousand processoring units at once by making use of the Message Passing Interface(MPI) to equip us with parallel performance that can scale very well. Incorporation of forced turbulence within PLUTO will provide for major benefits for the scientific computing community and will be essential in studies of ISM and IGM physics. We have augmented, tested and validated the module under di↵erent conditions and applied it to study the energy dissipation rate, the fractal morphology of the fluid at di↵erent driving acceleration fields. We employ a Helmholtz decomposition on a time correlated random acceleration field created using the Orstein Uhlenbeck process in the injection scale and solve fluid equations (Hydro-Dynamic and Magneto Hydro-Dynamic) under ideal or controlled viscosity conditions to stufy fluid flows in Astronomical envi ronments.