On the Description of Waves in TwoPhase Gaseous Systems
Abstract
We summarize the properties of waves in a mixture of a diffuse phase (phase I [P I]) and a dense phase (phase II [P II]) by linear analysis, introducing a method of multiphase fluid dynamics (MPFD). Each phase has different density and temperature, but pressure balance is assumed among them. This condition corresponds to the twophase model of interstellar matter.
First, we show that two distinct modes coexist in a twophase mixture. One mode (the fmode) corresponds to a sound wave, and the other mode (the smode) to a void wave. Void waves are known to be fundamental waves in multiphase flows. In particular, our smode appears when the P I medium compressed by blobs (P II) repels the blobs. According to a recent work by the present author, through this smode of void waves, it is suggested that smallscale structures appear in a selfgravitating twophase gas mixture.
Next, we perform numerical analysis and summarize the properties of both modes. In particular, in the smode, the phase velocity is not varied even if the γ_{I} (adiabatic exponent of P I gas) has various values. However, for large α, the phase velocity of the smode is reduced. Here α denotes the volume fraction of phase I. Thus, we find not only that the smode is insensitive to the intrinsic compressibility of the ambient gas around the blobs (γ_{I} effect) but also that the amount of P I medium compressed by ballistic motions of P II (the α effect) is effective in propagation of the smode in a twophase interstellar gas mixture.
 Publication:

The Astrophysical Journal
 Pub Date:
 January 1997
 DOI:
 10.1086/303429
 Bibcode:
 1997ApJ...474..308K
 Keywords:

 Hydrodynamics;
 ISM: General;
 Waves