[FLASH-USERS] different equations of states for different species

[liu zhigang]

Hi, Zhang
I am also interested in the simulation within a “cold start”. In my opinion, the main reason for these problems is that FLASH is based on the MHD equation in Eulerian coordinates. Accurate material interface tracking should be performed under the Lagrangian framework, of course, it will fail in the presence of large deformations. In Euler coordinates, a more accurate solution of multiphase flow requires the introduction of interface reconstruction, such as VOF and MOF method, which is not supported in FLASH. In addition, a thermodynamic closed model in the mixed cell needs to be given for the interface tracking problem, as mentioned by Maksim Kozlov. In FLASH, a simple weighted sum of different species is used. And there are some more completed closure models for multi-material cells in other publications, like the pressure relaxation model. However, to implement new physics model in FLASH, lots of code modifications will be required.

Regards,
Liu

发件人: Zhang Daoyuan<mailto:zdy0903 at stu.xjtu.edu.cn>
发送时间: 2021年2月21日 10:28
收件人: flash-users at flash.uchicago.edu<mailto:flash-users at flash.uchicago.edu>
主题: [FLASH-USERS] different equations of states for different species

Hi all!
  This question, which is brought by Maksim Kozlov is what I want to ask for a long time. FLASH can use tabulated 3T EOS in IONMIX4 format. However, as far I as know, the electron pressure is negative (Pele<0) in the liquid-vapor state (~2000K) for the materials like Al, Cu, etc. I find the negative electron pressure in PropaceEOS data (from Prism Company). And FLASH do not support the electron pressure, as mentioned in the previous question

“If either one of your pressures or one of your energies goes down to zero or below anywhere, you may be in trouble anyway. Various places in the implementation of Hydro, in particular, may fail when that happens.

Klaus”

  If we want to generate a simulation within a “cold start”, we need to deal with the material in liquid-vapor state. Maybe one solution is to use a 1T simulation (this is what I have done, change the ideal EOS file to an interpolation program and input a 1T EOS table. Just like Kozlov did). This is because total pressure is always positive in 1T EOS, and of course, we can assume Tele=Tion for the liquid-vapor material.
  I don’t know if it appropriate to do this. And is anybody knows how I can use 3T EOS if the electron pressure is negative.

  “A crucial question for this kind of thing: How do you want those "two different EoS" to be combined in cells that contain both species?”

  This is also a question that puzzled me. For the 3T simulations, like LaserSlab, it uses 2 species, “Al” and “He”. (However the “He” in LaserSlab is not the real helium gas, it is extremely low-density material which is treated as vacuum.) How can we understand the interface between these two species? Just like the attached picture shows, “1” is Al and “0” is gas, how can we understand “0.5”?

  Thank you very much for all the answers!

Yours

Zhang



[cid:13fc1012$1$177c26aaf14$Coremail$zdy0903$stu.xjtu.edu.cn]


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