On the Structure of the Turbulent Interstellar Clouds
  {It is well established that the atomic interstellar hydrogen is filling the
galaxies and constitutes the building blocks of molecular clouds.} {To
understand the formation and the evolution of molecular clouds, it is necessary
to investigate the dynamics of turbulent and thermally bistable as well as
barotropic flows.} {We perform high resolution 3-dimensional hydrodynamical
simulations of 2-phase, isothermal and polytropic flows.} {We compare the
density PDF and Mach number density relation in the various simulations and
conclude that 2-phase flows behave rather differently than polytropic flows. We
also extract the clumps and study their statistical properties such as mass
spectrum, mass-size relation and internal velocity dispersion. In each case, it
is found that the behaviour is well represented by a simple powerlaw. While the
various exponents inferred are very similar for the 2-phase, isothermal and
polytropic flows, we nevertheless find significant differences, such as for
example the internal velocity dispersion which is smaller for 2-phase flows.}
{The structures statistics are very similar to what has been inferred from
observations, in particular the mass spectrum, the mass-size relation and the
velocity dispersion-size relation are all powerlaws whose indices well agree
with the observed values. Our results suggest that in spite of various
statistics being similar for 2-phase and polytropic flows, they nevertheless
present significant differences, stressing the necessity to consider the proper
thermal structure of the interstellar atomic hydrogen for computing its
dynamics as well as the formation of molecular clouds.}
