[FLASH-USERS] Question / potential bug in EOS

[pchang]

Hi Dean,
Thank you. The number seems to be reasonable. I thought by turning off 
the radiation, I don't need to worry about the radiation pressure. But I 
guess I am wrong.

Po-Yu

On 11/9/2015 1:50 PM, Dean Townsley wrote:
> 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
>>
>>
>


-- 
Po-Yu Chang

Postdoctoral Associate
The Department of Energy's Advanced Research Projects Agency-Energy (ARPA-E)
Department of Mechanical Engineering,
Fusion Science Center for Extreme States of Matter,
Laboratory for Laser Energetics
University of Rochester
250 East River Road
Rochester, New York 14623
Phone: (585) 273-5179
FAX: (585) 275-5960
pchang at lle.rochester.edu