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Equation of State

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Actionbot edited this page Oct 22, 2024 · 13 revisions

This page describes various equation of states (EoS) supported by the compilation option EOS.

EOS_GAMMA

An ideal-gas EoS with a constant adiabatic index GAMMA.

EOS_ISOTHERMAL

An isothermal EoS with a constant sound speed set by MOLECULAR_WEIGHT and ISO_TEMP.

EOS_COSMIC_RAY

A cosmic-ray EoS with an adiabatic index for fluid GAMMA and an effective adiabatic index for cosmic rays GAMMA_CR. Must enable COSMIC_RAY.

EOS_TAUBMATHEWS

A special relativistic EoS with a variable gamma by Taub 1948 and Mathews 1971. Must enable SRHD.

EOS_USER

Follow the steps below to define your EoS when adding a new simulation named NewProblem.

  1. Go to the new test problem folder and copy the EoS template.

    cd src/TestProblem/Hydro/NewProblem
cp ../../../EoS/User_Template/CPU_EoS_User_Template.cpp CPU_EoS_NewProblem.cpp
ln -s CPU_EoS_NewProblem.cpp GPU_EoS_NewProblem.cu # CPU/GPU share the same source file

  2. Edit the EoS source file CPU_EoS_NewProblem.cpp.

    1. Rename User_Template as NewProblem. For example, with the vim editor you can do %s/User_Template/NewProblem/g in the command line mode.

    2. [Optional] Set the auxiliary array AuxArray[] in void EoS_SetAuxArray_NewProblem(). This array must be constant across the simulation period and domain and will be passed to all EoS conversion functions (see below) automatically. The array size is set by EOS_NAUX_MAX in include/Macro.h (default is 10).

    3. Implement the following EoS conversion functions.

      • EoS_DensEint2Pres_NewProblem(): convert gas mass density and internal energy density to gas pressure.
      • EoS_DensPres2Eint_NewProblem(): convert gas mass density and pressure to gas internal energy density.
      • EoS_DensPres2CSqr_NewProblem(): convert gas mass density and pressure to sound speed squared.
      • EoS_DensEint2Temp_NewProblem(): convert gas mass density and internal energy to gas temperature [OPTIONAL].
      • EoS_DensTemp2Pres_NewProblem(): convert gas mass density and temperature to gas pressure [OPTIONAL].
      • EoS_General_NewProblem(): general conversion between user-specified input and output variables [OPTIONAL].

      Caution:

      • All conversion functions must be thread-safe and not use any global variable.
      • When a conversion function fails, it is recommended to return NAN in order to trigger auto-corrections such as OPT__1ST_FLUX_CORR and AUTO_REDUCE_DT.

  3. Edit the problem source file Init_TestProb_Hydro_NewProblem.cpp to enable this new EoS.

    1. Put the following function prototype on the top of this file.

      void EoS_Init_NewProblem();

    2. Set the EoS function pointer in Init_TestProb_Hydro_NewProblem().

    EoS_Init_Ptr = EoS_Init_NewProblem;

  4. Make sure to set EOS=EOS_USER in the Makefile.


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