Radiative gas dynamics in the transonic regime
Abstract
The three equations specifying conservations of mass, momentum, and energy in radiating gases, coupled to the equation of radiative transfer, are examined for flow velocities approaching the local speed of sound. It is found that time-dependent terms are essential to any analysis of this transonic regime. In particular, it is found that wave-type perturbations start to amplify, rather than damp, when the flow velocity exceeds a critical value v(crit), where v(crit) is approximately 80 percent of the local thermal speed. These amplifications exhibit an e factor increase over a time scale of order 40 s for solar-type atmospheres, and eventually reach a magnitude which invalidates the concept of a steady state gaseous flow. Further, the work done by pressure forces during a cycle of these wave disturbances generates a nonzero heating of the gas when the temperature fluctuations lead the velocity fluctuations as is the case when the gas radiates. This heating mechanism could explain some aspects of stellar chromospheric temperature increases.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- February 1985
- DOI:
- 10.1086/162896
- Bibcode:
- 1985ApJ...289..363C
- Keywords:
-
- Computational Astrophysics;
- Gas Dynamics;
- Radiative Transfer;
- Stellar Atmospheres;
- Chromosphere;
- Conservation Equations;
- Damping;
- Energy Transfer;
- Flow Velocity;
- Subsonic Flow;
- Transonic Flow;
- Astrophysics