Issue |
A&A
Volume 539, March 2012
|
|
---|---|---|
Article Number | A147 | |
Number of page(s) | 14 | |
Section | Numerical methods and codes | |
DOI | https://doi.org/10.1051/0004-6361/201117984 | |
Published online | 08 March 2012 |
Accuracy and efficiency of raytracing photoionisation algorithms
Argelander-Institut für Astronomie, Auf dem Hügel 71, 53121 Bonn, Germany
e-mail: jmackey@astro.uni-bonn.de
Received: 31 August 2011
Accepted: 1 February 2012
Three non-equilibrium photoionisation algorithms for hydrodynamical grid-based simulation codes are compared in terms of accuracy, timestepping criteria, and parallel scaling. Explicit methods with first-order time accuracy for photon conservation must use very restrictive timestep criteria to accurately track R-type ionisation fronts. A second-order accurate algorithm is described which, although it requires more work per step, allows much longer timesteps and is consequently more efficient. Implicit methods allow ionisation fronts to cross many grid cells per timestep while maintaining photon conservation accuracy. It is shown, however, that errors are much larger for multi-frequency radiation than for monochromatic radiation with the implicit algorithm used here, and large errors accrue when an ionisation front crosses many optical depths in a single step. The accuracy and convergence rates of the different algorithms are tested with a large number of timestepping criteria to identify the best criterion for each algorithm. With these criteria selected, the second-order explicit algorithm is the most efficient of the three, and its parallel scaling is significantly better than that of the implicit algorithm. The upgrade from first- to second-order accuracy in explicit algorithms could be made very simply to fixed-grid and adaptive mesh-refinement codes which currently use a first-order method.
Key words: radiative transfer / methods: numerical / Hii regions
© ESO, 2012
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.