VETTAM: A scheme for radiation hydrodynamics with adaptive mesh refinement using the variable Eddington tensor method

Abstract

We present Variable Eddington Tensor-closed Transport on Adaptive Meshes (\texttt{VETTAM}), a new algorithm to solve the equations of radiation hydrodynamics (RHD) with support for adaptive mesh refinement (AMR) in a frequency-integrated, two-moment formulation. The method is based on a non-local Variable Eddington Tensor (VET) closure computed with a hybrid characteristics scheme for ray tracing. We use a Godunov method for the hyperbolic transport of radiation with an implicit backwards-Euler temporal update to avoid the explicit timestep constraint imposed by the light-crossing time, and a fixed-point Picard iteration scheme to handle the nonlinear gas-radiation exchange term, with the two implicit update stages jointly iterated to convergence. We also develop a modified wave-speed correction method for AMR, which we find to be crucial for obtaining accurate results in the diffusion regime. We demonstrate the robustness of our scheme with a suite of pure radiation and RHD tests, and show that it successfully captures the streaming, static diffusion, and dynamic diffusion regimes and the spatial transitions between them, casts sharp shadows, and yields accurate results for rates of momentum and energy exchange between radiation and gas. A comparison between different closures for the radiation moment equations, with the Eddington approximation (0th-moment closure) and the $M_1$ approximation (1st-moment closure), demonstrates the advantages of the VET method (2nd-moment closure) over the simpler closure schemes. \texttt{VETTAM} has been coupled to the AMR \texttt{FLASH} (magneto-)hydrodynamics code and we summarize by reporting performance features and bottlenecks of our implementation.

23 pages, 15 figures. Accepted for publication in MNRAS

References in corpus (22)

• Array Programming with NumPy
• Theory of Core-Collapse Supernovae
• Modeling Collapse and Accretion in Turbulent Gas Clouds: Implementation and Comparison of Sink Particles in AMR and SPH
• The RAGE radiation-hydrodynamic code
• A scheme for radiation pressure and photon diffusion with the M1 closure in RAMSES-RT
• Equations and Algorithms for Mixed Frame Flux-Limited Diffusion Radiation Hydrodynamics
• A radiative transfer scheme for cosmological reionization based on a local Eddington tensor
• Magnetohydrodynamic Simulations of Active Galactic Nucleus Disks and Jets
• Magnetohydronamic Evolution of HII Regions in Molecular Clouds: Simulation Methodology, Tests, and Uniform Media
• An Unstable Truth: How Massive Stars get their Mass
• Atmospheric Regimes and Trends on Exoplanets and Brown Dwarfs
• Radiation Feedback in ULIRGS: Are Photons Movers and Shakers?
• Formation and Evolution of Disks around Young Stellar Objects
• An Implicit Finite Volume Scheme to Solve the Time Dependent Radiation Transport Equation Based on Discrete Ordinates
• Zooming in on Individual Star Formation: Low- and High-mass Stars
• Radiation-hydrodynamical simulations of massive star formation using Monte Carlo radiative transfer: I. Algorithms and numerical methods
• Hybrid Adaptive Ray-Moment Method (HARM${}^2$): A Highly Parallel Method for Radiation Hydrodynamics on Adaptive Grids
• Saturation of the MRI in Strongly Radiation Dominated Accretion Disks
• A general hybrid radiation transport scheme for star formation simulations on an adaptive grid
• Makemake + Sedna: A Continuum Radiation Transport and Photoionization Framework for Astrophysical Newtonian Fluid Dynamics
• Radiation hydrodynamics including irradiation and adaptive mesh refinement with AZEuS. I. Methods
• A high-performance and portable asymptotic preserving radiation hydrodynamics code with the M1 model