The stiffened gas equation of state models liquids using assumptions of an ideal gas with respect to a reference pressure, assuming that \(C_p\) and \(C_v\) are constant. For the current implementation this results in an EOS that is independent of the gas species. The EOS can be described with \(\gamma, C_p\) and \(p^0\).

Input Default Value Argument
\(\gamma\) 1.932 -gamma
\(C_p\) 8095.08 J/kg/K -Cp
\(p^0\) \(1.1645 \times 10^9\) Pa -p0

Decode State

The decode state function computes the required values to compute fluxes from the Euler conserved variables.

Internal Energy

\[\begin{eqnarray} e = e_t - KE \end{eqnarray}\]


\[\begin{eqnarray} p = (\gamma - 1.0) \rho e - \gamma p^0 \end{eqnarray}\]

Speed of Sound

\[\begin{eqnarray} a = \sqrt{\gamma (p+p^0)/\rho} \end{eqnarray}\]


The temperature function computes T from \(e_t\), \(\rho\vector{u}\), and \(\rho\).

\[\begin{eqnarray} T = (e - \frac{p^0}{\rho}) \frac{\gamma}{C_p} \end{eqnarray}\]


  • Chang, C. H. and Liou, M. S. (2007), “A robust and accurate approach to computing compressible multiphase flow: Stratified flow model and AUSM+up scheme.” Journal of Computational Physics, 225, 840-873.