432 research outputs found
The Density Probability Distribution in Compressible Isothermal Turbulence: Solenoidal versus Compressive Forcing
The probability density function (PDF) of the gas density in turbulent
supersonic flows is investigated with high-resolution numerical simulations. In
a systematic study, we compare the density statistics of compressible
turbulence driven by the usually adopted solenoidal forcing (divergence-free)
and by compressive forcing (curl-free). Our results are in agreement with
studies using solenoidal forcing. However, compressive forcing yields a
significantly broader density distribution with standard deviation ~3 times
larger at the same rms Mach number. The standard deviation-Mach number relation
used in analytical models of star formation is reviewed and a modification of
the existing expression is proposed, which takes into account the ratio of
solenoidal and compressive modes of the turbulence forcing.Comment: 5 pages, 3 figures, accepted to ApJL, simulation movies available at
http://www.ita.uni-heidelberg.de/~chfeder/videos.shtml?lang=e
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