15.4 Radiation-Flux-Limiter Aware Hydrodynamics

RadFLAH is a variant of hydrodynamics meant to be used together with an implementation of radiation transport that is based on flux-limited diffusion. The hydro is “aware” of the flux limiter and has modified and additional terms.

The implementation is included under physics/Hydro/HydroMain/unsplit_rad. This variant implements additional terms in the FLD Rad-Hydro equations to handle streaming and transition-to-streaming regimes better (including in particular effects of radiation pressure) than the regular version of unsplit Hydro used for HEDP simulations and similar applications.

Setup with shortcut +uhd3tR instead of +uhd3t . This has had limited testing, mostly in 1D spherical geometry.

The current implementation assumes that the fluid is described by two temperatures (matter+radiation), and thus the “electron” componenent really represents “matter”; we hope to remove reliance on this assumption in the future. With this assumption in place, this code has to be used together with a “MatRad3” implementation of multiTemp Eos. Ssee also physics/Eos/Eos/EosMain/multiTemp/MatRad3/README.

The current implementation assumes there is only one radiation group (gray opacities). We may extend this in the future.

Currently there is no equivalent variant for MHD - this should be straightforward to implement, and we plan to provide this in the future (probably under unsplit_rad/MHD_StaggeredMesh).

More information will be included here after draft publication of Chatzopoulos and Weide (2017).

Several example setups are available under Simulation/SimulationMain/radflaHD/.