StiffenedGasTwoPhaseFluidPropertiesTest.C

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#include "StiffenedGasTwoPhaseFluidPropertiesTest.h"
#include "SinglePhaseFluidPropertiesTestUtils.h"

TEST_F(StiffenedGasTwoPhaseFluidPropertiesTest, test)
{
  Real p = 101325; // Pa

  /*
   * The following reference gives the saturation state to have equal Gibbs
   * free enthalpy between the 2 phases.
   *
   * Ray A. Berry, Richard Saurel, Olivier LeMetayer
   * The discrete equation method (DEM) for fully compressible, two-phase flow
   *   in ducts of spatially varying cross-section
   * Nuclear Engineering and Design 240 (2010) p. 3797-3818
   *
   * Therefore, it should be asserted that the nonlinear solver for the saturation
   * temperature returns a state for which this is true.
   */
  const Real T_sat = _fp->T_sat(p);
  // liquid
  const Real rho_liquid = _fp_liquid->rho_from_p_T(p, T_sat);
  const Real v_liquid = 1.0 / rho_liquid;
  const Real e_liquid = _fp_liquid->e_from_p_rho(p, rho_liquid);
  const Real g_liquid = _fp_liquid->g_from_v_e(v_liquid, e_liquid);
  // vapor
  const Real rho_vapor = _fp_vapor->rho_from_p_T(p, T_sat);
  const Real v_vapor = 1.0 / rho_vapor;
  const Real e_vapor = _fp_vapor->e_from_p_rho(p, rho_vapor);
  const Real g_vapor = _fp_vapor->g_from_v_e(v_vapor, e_vapor);

  REL_TEST(g_liquid, g_vapor, 1e-5);

  // ensure that p_sat(T_sat(p)) is the inverse of T_sat(p)
  REL_TEST(_fp->p_sat(T_sat), p, 1e-14);

  // test derivative along saturation curve using FD approximation
  Real dT_dPsat = _fp->dT_sat_dp(p);
  Real dp = 1e1;
  Real dT_dPsat_fd = (_fp->T_sat(p + dp) - _fp->T_sat(p - dp)) / (2 * dp);

  EXPECT_NEAR(dT_dPsat, dT_dPsat_fd, 1e-14);

  EXPECT_NEAR(_fp->p_critical(), 22.09e6, 1e-15);

  // This value was verified to match the value from IAPWS95 fluid properties
  REL_TEST(_fp->sigma_from_T(300.0), 0.0716859625271626, REL_TOL_SAVED_VALUE);

  {
    const Real T = 300.0;
    const Real T_pert = T * 1e-6;
    const Real dsigma_dT_fd =
        (_fp->sigma_from_T(T + T_pert) - _fp->sigma_from_T(T - T_pert)) / (2.0 * T_pert);
    REL_TEST(_fp->dsigma_dT_from_T(T), dsigma_dT_fd, REL_TOL_DERIVATIVE);
  }

  EXPECT_NEAR(_fp->T_triple(), _T_triple, 1e-14);
  EXPECT_NEAR(_fp->L_fusion(), _L_fusion, 1e-14);
}