Abstract
We present results from a systematic numerical study of the effect of turbulent velocity fluctuations on the thermal pressure distribution in thermally bistable flows. The turbulent fluctuations are characterized by their rms Mach number M (with respect to the warm medium) and the energy injection wavenumber, kfor. Our results are consistent with the picture that as either of these parameters is increased, the local ratio of turbulent crossing time to cooling time decreases, causing transient structures in which the effective behavior is intermediate between the thermal-equilibrium and adiabatic regimes. As a result, the effective polytropic exponent γe of the simulations ranges between ∼ 0.2 to ∼ 1.1, and the mean pressure of the diffuse gas is generally reduced below the thermal equilibrium pressure Peq, while that of the dense gas is increased with respect to Peq. The fraction of high-density zones (n > 7.1 cm-3) with P > 104 K cm-3 increases from roughly 0.1% at kfor = 2 and M = 0.5 to roughly 70% for kfor = 16 and M = 1.25. A preliminary comparison with the recent pressure measurements of Jenkins (2004) in CI favors our case with M = 0.5 and kfor = 2.
