Max Gronke

Gases in astrophysics are often multiphase, that is some colder clumps are embedded in a “bath” of hotter material. In addition, astrophysical gases are very commonly turbulent, that is, they are not standing still but there is some random motion in them.

In arXiv:2107.13012 we studied what happens to the gas clumps because of turbulence. To do so, we ran 3D hydrodynamical simulations in which we placed a cold gas clump, in a hot, turbulent box. Below, I uploaded some visualizations from these simulations.

As you can see the turbulence mixed the cold gas into the hot gas, and towards the end of the simulation no cold gas is left.

For a cloud that is 100 times bigger, the situation looks very different:

The cold gas does still fragment, but the pieces spread and survive, and in fact the total cold gas volume increases with time.

An interesting thing happens if we look at a gas cloud larger than the first, but smaller than the second one:

There, some clouds survive while others die. This is due to the stochastic nature of the turbulence they’re subject to.

If we place several very small clumps, they also die:

For larger overdensity (chi ~ 1000):