[FLASH-USERS] Question / potential bug in EOS

[Dean Townsley]

Hi Po-Yu,

Just putting your numbers into the equation for radiation pressure, 
(a*T^4)/3, it seems that you are not including the radiation pressure 
term in your other calculations of the pressure, but flash is.  I think 
it is not uncommon for some tabulations to assume that you will add the 
radiation pressure separately.  i.e. they only tabulate the gas 
contribution to the pressure.

I don't know a lot about the mult-T solver, but I expect it is pretty 
important that it include the radiation pressure for the photon field.

Dean

On 11/09/2015 11:25 AM, pchang wrote:
> Hi all,
> I am benchmarking Flash to a 1D code in our lab and the calculated 
> numbers and see if they give the same result. And I found some results 
> that indicates some issues / potential bug in EOS.
> In my test, I setup an initial temperature with an initial density of 
> D2 gas. To simplify the problem, I used fully ionized ideal gas model, 
> which I believe it's what eos_gam stand for. The eos mode I had were 
> eosModeInit="dens_temp_gather" and eosMode="dens_ie_gather". During 
> the test, I kept the gas density fixed to be 1.6mg/cc. Then I varied 
> the initial temperature. Since I used +mtmmmt in my setup, so I need 
> to give the electron, the ion, and the radiation temperature, but I 
> kept them all the same to each other during the test. When I had the 
> temperature equal to 2.9e2 Kelvin (0.025eV), it gave a pressure of  
> ~4e7 dyne/cm2. This number matches the 1D code and the calculated 
> pressure using the ideal gas model. Then, I increased the temperature 
> and see what's the pressure I got. In ideal gas model, the pressure 
> scales linearly versus temperature. However, when I had the 
> temperature of 2.9e6 Kelvin (250eV), the pressure deviated from our 1D 
> code and the ideal gas model. In stead of getting ~4e11 dyne/cm2, I 
> got 5.7e11 dyne/cm2. When I increased the temperature to 2.9e7 Kelvin 
> (2.5keV), the pressure was 1.8e15 dyne/cm2 instead of ~4e12 dyne/cm2 
> from ideal gas model. The much higher pressure can make big impact on 
> hydrodynamic! In fact I tried using tabulated sesame table, they gave 
> the same result!
>
> I don't know if any encounter this issues? Is it a potential bug in 
> the eos package?
>
> Thanks,
>
> Po-Yu
>
>