Equation of State - hyschive/gamer-fork GitHub Wiki

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

EOS_GAMMA: constant-gamma EoS
EOS_ISOTHERMAL: isothermal EoS
EOS_COSMIC_RAY: cosmic-ray EoS
EOS_TAUBMATHEWS: special relativistic EoS
EOS_USER: user-specified 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.

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

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 .

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;
```
Make sure to set EOS=EOS_USER in the Makefile.