[FLASH-USERS] Problem with hydro

[Klaus Weide]

On Thu, 4 Dec 2014, pchang wrote:

> Hi all,
> I am using Flash to simulate the HEDP problem. Recently, I had following
> tests:
> Start with the LaserSlab example. Turn off the radiation, heat exchange,
> conduction, laser by setting:
> rt_useMGD=.false.
> useOpacity=.false.
> useEnergyDeposition=.false.
> ed_useLaserIO=.false.
> useDiffuse=.false.
> useConductivity=.false.
> diff_useEleCond=.false.
> useHeatexchange=.false.
> 
> I kept the hydro to be on by setting:
> useHydro=.true.
> 
> Since there was no energy in/out, I expected nothing would change in the
> simulation. However, the temperature in the low density gas right next to the
> target dropped!
> If I turned off the hydro by setting useHydro=.false. , the temperature did
> not change as expected. I tried different combinations of turning on and off
> of different physics. I found it's mainly from the hydro.

Po-Yu,

This appears to be as expected, if your initial conditions are such that 
there are regions with different pressures (for example, target material 
vs. gas or "vacuum" in many HEDP simulations). Hydro will start moving 
matter. Movement results in compression and/or expansion of material, 
which results in changes of temperature. (All this without even thinking 
of shocks).

Klaus