[Test] Switch real gas derivative tests to thermo consistency tests

Removed `getIsothermalCompressibility` and `getThermalExpansionCoeff` from `PengRobinson_Test` and `RedlichKwongMFTP_Test`.
Add finite difference tests to `TestConsistency` as `betaT_eq_minus_dmv_dP_const_T_div_mv` and `alphaV_eq_dmv_dT_const_P_div_mv`.

Author: corykinney

test/thermo/PengRobinson_Test.cpp

@@ -179,58 +179,6 @@ TEST_F(PengRobinson_Test, CoolPropValidate)
     }
 }
 
-TEST_F(PengRobinson_Test, getIsothermalCompressibility)
-{
-    const double isothermalCompressibility[10] = {
-        2.0565735288179827e-06, 
-        2.043354114849639e-06, 
-        2.0336631623657743e-06, 
-        2.0263828696824072e-06,
-        2.0208047779848385e-06, 
-        2.0164611841648566e-06,
-        2.0130329255806156e-06, 
-        2.010296131734592e-06, 
-        2.0080900822010764e-06, 
-        2.0062970726140575e-06
-    };
-
-    double p = 5e5;
-
-    for(int i=0; i<10; i++)
-    {
-        const double temp = 300 + i*25;
-        set_r(1.0);
-        test_phase->setState_TP(temp, p);
-        EXPECT_NEAR(test_phase->isothermalCompressibility(),isothermalCompressibility[i],1.e-12);
-    }
-}
-
-TEST_F(PengRobinson_Test, getThermalExpansionCoeff)
-{
-    const double thermalExpansionCoeff[10] = {
-        0.0036236953242238055, 
-        0.0032907286131624216, 
-        0.003018150217266326, 
-        0.0027901653673486353, 
-        0.0025961927676142714, 
-        0.0024288429329921953, 
-        0.0022827789874782295, 
-        0.0021540380684750378, 
-        0.0020396082523816846, 
-        0.0019371545393275069
-    };
-
-    double p = 5e5;
-
-    for(int i=0; i<10; i++)
-    {
-        const double temp = 300 + i*25;
-        set_r(1.0);
-        test_phase->setState_TP(temp, p);
-        EXPECT_NEAR(test_phase->thermalExpansionCoeff(),thermalExpansionCoeff[i],1.e-9);
-    }
-}
-
 TEST(PengRobinson, lookupSpeciesProperties)
 {
     AnyMap phase_def = AnyMap::fromYamlString(

test/thermo/RedlichKwongMFTP_Test.cpp

@@ -110,58 +110,6 @@ TEST_F(RedlichKwongMFTP_Test, setTP)
     }
 }
 
-TEST_F(RedlichKwongMFTP_Test, getIsothermalCompressibility)
-{
-    const double isothermalCompressibility[10] = {
-        2.050805848598598e-06, 
-        2.039662581125248e-06, 
-        2.0314744830510903e-06, 
-        2.0253016382569196e-06, 
-        2.020549462982612e-06, 
-        2.0168263925524153e-06, 
-        2.013865922214169e-06, 
-        2.0114815945776956e-06, 
-        2.009539860089652e-06,
-        2.0079431083026355e-06
-    };
-
-    double p = 5e5;
-
-    for(int i=0; i<10; i++)
-    {
-        const double temp = 300 + i*25;
-        set_r(1.0);
-        test_phase->setState_TP(temp, p);
-        EXPECT_NEAR(test_phase->isothermalCompressibility(),isothermalCompressibility[i],1.e-12);
-    }
-}
-
-TEST_F(RedlichKwongMFTP_Test, getThermalExpansionCoeff)
-{
-    const double thermalExpansionCoeff[10] = {
-        0.003578413284819209, 
-        0.003257292385643213, 
-        0.0029931405440041577, 
-        0.00277129023136564, 
-        0.0025818659337611253, 
-        0.002417938630670952, 
-        0.0022744816978795736, 
-        0.0021477468339320253, 
-        0.002034873745423023, 
-        0.0019336365732413633
-    };
-
-    double p = 5e5;
-
-    for(int i=0; i<10; i++)
-    {
-        const double temp = 300 + i*25;
-        set_r(1.0);
-        test_phase->setState_TP(temp, p);
-        EXPECT_NEAR(test_phase->thermalExpansionCoeff(),thermalExpansionCoeff[i],1.e-9);
-    }
-}
-
 TEST_F(RedlichKwongMFTP_Test, critPropLookup)
 {
     // Check to make sure that RedlichKwongMFTP is able to properly calculate a and b

test/thermo/consistency.cpp

@@ -345,6 +345,56 @@ TEST_P(TestConsistency, dSdv_const_T_eq_dPdT_const_V) {
     }
 }
 
+TEST_P(TestConsistency, betaT_eq_minus_dmv_dP_const_T_div_mv)
+{
+    double betaT1;
+    try {
+        betaT1 = phase->isothermalCompressibility();
+    } catch (NotImplementedError& err) {
+        GTEST_SKIP() << err.getMethod() << " threw NotImplementedError";
+    }
+
+    double T = phase->temperature();
+    double P1 = phase->pressure();
+    double mv1 = phase->molarVolume();
+    
+    double P2 = P1 * (1 + 1e-7);
+    phase->setState_TP(T, P2);
+    double betaT2 = phase->isothermalCompressibility();
+    double mv2 = phase->molarVolume();
+
+    double betaT_mid = 0.5 * (betaT1 + betaT2);
+    double mv_mid = 0.5 * (mv1 + mv2);
+    double betaT_fd = -1 / mv_mid * (mv2 - mv1) / (P2 - P1);
+
+    EXPECT_NEAR(betaT_fd, betaT_mid, max({rtol_fd * betaT_mid, rtol_fd * betaT_fd, atol}));
+}
+
+TEST_P(TestConsistency, alphaV_eq_dmv_dT_const_P_div_mv)
+{
+    double alphaV1;
+    try {
+        alphaV1 = phase->thermalExpansionCoeff();
+    } catch (NotImplementedError& err) {
+        GTEST_SKIP() << err.getMethod() << " threw NotImplementedError";
+    }
+
+    double P = phase->pressure();
+    double T1 = phase->temperature();
+    double mv1 = phase->molarVolume();
+
+    double T2 = T1 * (1 + 1e-7);
+    phase->setState_TP(T2, P);
+    double alphaV2 = phase->thermalExpansionCoeff();
+    double mv2 = phase->molarVolume();
+
+    double alphaV_mid = 0.5 * (alphaV1 + alphaV2);
+    double mv_mid = 0.5 * (mv1 + mv2);
+    double alphaV_fd = 1 / mv_mid * (mv2 - mv1) / (T2 - T1);
+
+    EXPECT_NEAR(alphaV_fd, alphaV_mid, max({rtol_fd * alphaV_mid, rtol_fd * alphaV_fd, atol}));
+}
+
 // ---------- Tests for consistency of standard state properties ---------------
 
 TEST_P(TestConsistency, hk0_eq_uk0_plus_p_vk0)