A flux-limited diffusion theory

Abstract.Solving radiative transfer problems with ray casting methods is compared with the commonly used 'Flux Limited Diffusion' approximation. Whereas ray casting produces solutions that converge to the exact one as the number of rays is increased, flux-limited-diffusion is fundamentally a 'look-alike' method, which produces solutions that are reminiscent of the correct solution but which cannot be made to converge to it.

Section: Flux Limited Diffusionmentioning

confidence: 56%

Section: Introductionmentioning

confidence: 99%

Ray Casting and Flux Limited Diffusion

Nordlund¹

2010

“…Many choices for the function λ are possible; the most common one in astrophysical applications is the Levermore & Pomraning (1981) …”

Section: Types Of Moment Methodsmentioning

confidence: 99%

Star Formation with Adaptive Mesh Refinement Radiation Hydrodynamics

Krumholz

2010

Abstract. I provide a pedagogic review of adaptive mesh refinement (AMR) radiation hydrodynamics (RHD) methods and codes used in simulations of star formation, at a level suitable for researchers who are not computational experts. I begin with a brief overview of the types of RHD processes that are most important to star formation, and then I formally introduce the equations of RHD and the approximations one uses to render them computationally tractable. I discuss strategies for solving these approximate equations on adaptive grids, with particular emphasis on identifying the main advantages and disadvantages of various approximations and numerical approaches. Finally, I conclude by discussing areas ripe for improvement.

“…The final ingredient for solving the energy balance in the atmosphere is a closure relation linking the flux F back to the radiation energy density. Here we utilize the flux-limited diffusion (FLD) approximation of Levermore & Pomraning (1981), where…”

Section: Navier-stokes Equationsmentioning

confidence: 99%

“…Between these limits, Equation 2.5 is chosen to approximate the full radiative transfer models of Levermore & Pomraning (1981).…”

Section: Navier-stokes Equationsmentioning

confidence: 99%

Radiative Hydrodynamical Studies of Irradiated Atmospheres

Dobbs-Dixon

2008

Abstract. Transiting planets provide a unique opportunity to study the atmospheres of extrasolar planets. Radiative hydrodynamical models of the atmosphere provide a crucial link between the physical characteristics of the atmosphere and the observed properties. Here I present results from 3D simulations which solve the full Navier-Stokes equations coupled to a flux-limited diffusion treatment of radiation transfer. Variations in opacity amongst models leads to a variation in the temperature differential across the planet, while atmospheric dynamics becomes much more variable at longer orbital periods. I also present 3D radiative simulations illustrating the importance of distinguishing between optical and infrared opacities.