Zusammenfassung
To make relevant predictions about observable emission, hydrodynamical
simulation codes must employ schemes that account for radiative losses, but the
large dimensionality of accurate radiative transfer schemes is often
prohibitive. Stamatellos and collaborators introduced a scheme for smoothed
particle hydrodynamics (SPH) simulations based on the notion of polytropic
pseudo-clouds that uses only local quantities to estimate cooling rates. The
computational approach is extremely efficient and works well in cases close to
spherical symmetry, such as in star formation problems. Unfortunately, the
method, which takes the local gravitational potential as an input, can be
inaccurate when applied to non-spherical configurations, limiting its
usefulness when studying disks or stellar collisions, among other situations of
interest. Here, we introduce the "pressure scale height method," which
incorporates the fluid pressure scale height into the determination of column
densities and cooling rates, and show that it produces more accurate results
across a wide range of physical scenarios while retaining the computational
efficiency of the original method. The tested models include spherical
polytropes as well as disks with specified density and temperature profiles. We
focus on applying our techniques within an SPH code, although our method can be
implemented within any particle-based Lagrangian or grid-based Eulerian
hydrodynamic scheme. Our new method may be applied in a broad range of
situations, including within the realm of stellar interactions, collisions, and
mergers.
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