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Fix Redlich-Kwong partial molar properties #1218

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merged 2 commits into from
Mar 18, 2022
Merged

Fix Redlich-Kwong partial molar properties #1218

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b7f40b2
[Thermo] Remove incorrect partialMolarCp from RedlichKwong
speth Mar 14, 2022
c72f095
[Thermo] Correct RedlichKwong::getPartialMolarIntEnergies
speth Mar 14, 2022
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4 changes: 3 additions & 1 deletion include/cantera/thermo/RedlichKwongMFTP.h
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Original file line number Diff line number Diff line change
Expand Up @@ -117,7 +117,9 @@ class RedlichKwongMFTP : public MixtureFugacityTP
virtual void getPartialMolarEnthalpies(doublereal* hbar) const;
virtual void getPartialMolarEntropies(doublereal* sbar) const;
virtual void getPartialMolarIntEnergies(doublereal* ubar) const;
virtual void getPartialMolarCp(doublereal* cpbar) const;
virtual void getPartialMolarCp(double* cpbar) const {
throw NotImplementedError("RedlichKwongMFTP::getPartialMolarCp");
}
virtual void getPartialMolarVolumes(doublereal* vbar) const;
//! @}

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35 changes: 23 additions & 12 deletions interfaces/cython/cantera/test/test_convert.py
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Original file line number Diff line number Diff line change
Expand Up @@ -663,20 +663,25 @@ def checkConversion(self, basename, cls=ct.Solution, ctiphases=(),

return ctiPhase, yamlPhase

def checkThermo(self, ctiPhase, yamlPhase, temperatures, tol=1e-7):
def checkThermo(self, ctiPhase, yamlPhase, temperatures, tol=1e-7, check_cp=True):
for T in temperatures:
ctiPhase.TP = T, ct.one_atm
yamlPhase.TP = T, ct.one_atm
cp_cti = ctiPhase.partial_molar_cp
cp_yaml = yamlPhase.partial_molar_cp
if check_cp:
cp_cti = ctiPhase.partial_molar_cp
cp_yaml = yamlPhase.partial_molar_cp
else:
with pytest.raises(ct.CanteraError):
yamlPhase.partial_molar_cp
h_cti = ctiPhase.partial_molar_enthalpies
h_yaml = yamlPhase.partial_molar_enthalpies
s_cti = ctiPhase.partial_molar_entropies
s_yaml = yamlPhase.partial_molar_entropies
self.assertNear(ctiPhase.density, yamlPhase.density)
for i in range(ctiPhase.n_species):
message = ' for species {0} at T = {1}'.format(i, T)
self.assertNear(cp_cti[i], cp_yaml[i], tol, msg='cp'+message)
if check_cp:
self.assertNear(cp_cti[i], cp_yaml[i], tol, msg='cp'+message)
self.assertNear(h_cti[i], h_yaml[i], tol, msg='h'+message)
self.assertNear(s_cti[i], s_yaml[i], tol, msg='s'+message)

Expand Down Expand Up @@ -779,13 +784,13 @@ def test_Redlich_Kwong_CO2(self):
ctiGas, yamlGas = self.checkConversion('co2_RK_example')
for P in [1e5, 2e6, 1.3e7]:
yamlGas.TP = ctiGas.TP = 300, P
self.checkThermo(ctiGas, yamlGas, [300, 400, 500])
self.checkThermo(ctiGas, yamlGas, [300, 400, 500], check_cp=False)

@utilities.slow_test
def test_Redlich_Kwong_ndodecane(self):
self.convert("nDodecane_Reitz", self.cantera_data_path)
ctiGas, yamlGas = self.checkConversion('nDodecane_Reitz')
self.checkThermo(ctiGas, yamlGas, [300, 400, 500])
self.checkThermo(ctiGas, yamlGas, [300, 400, 500], check_cp=False)
self.checkKinetics(ctiGas, yamlGas, [300, 500, 1300], [1e5, 2e6, 1.4e7],
1e-6)

Expand Down Expand Up @@ -889,20 +894,26 @@ def checkConversion(self, basename, cls=ct.Solution, ctmlphases=(),

return ctmlPhase, yamlPhase

def checkThermo(self, ctmlPhase, yamlPhase, temperatures, pressure=ct.one_atm, tol=1e-7):
def checkThermo(self, ctmlPhase, yamlPhase, temperatures, pressure=ct.one_atm,
tol=1e-7, check_cp=True):
for T in temperatures:
ctmlPhase.TP = T, pressure
yamlPhase.TP = T, pressure
cp_ctml = ctmlPhase.partial_molar_cp
cp_yaml = yamlPhase.partial_molar_cp
if check_cp:
cp_ctml = ctmlPhase.partial_molar_cp
cp_yaml = yamlPhase.partial_molar_cp
else:
with pytest.raises(ct.CanteraError):
yamlPhase.partial_molar_cp
h_ctml = ctmlPhase.partial_molar_enthalpies
h_yaml = yamlPhase.partial_molar_enthalpies
s_ctml = ctmlPhase.partial_molar_entropies
s_yaml = yamlPhase.partial_molar_entropies
self.assertNear(ctmlPhase.density, yamlPhase.density)
for i in range(ctmlPhase.n_species):
message = ' for species {0} at T = {1}'.format(ctmlPhase.species_names[i], T)
self.assertNear(cp_ctml[i], cp_yaml[i], tol, msg='cp'+message)
if check_cp:
self.assertNear(cp_ctml[i], cp_yaml[i], tol, msg='cp'+message)
self.assertNear(h_ctml[i], h_yaml[i], tol, msg='h'+message)
self.assertNear(s_ctml[i], s_yaml[i], tol, msg='s'+message)

Expand Down Expand Up @@ -1002,13 +1013,13 @@ def test_Redlich_Kwong_CO2(self):
ctmlGas, yamlGas = self.checkConversion('co2_RK_example')
for P in [1e5, 2e6, 1.3e7]:
yamlGas.TP = ctmlGas.TP = 300, P
self.checkThermo(ctmlGas, yamlGas, [300, 400, 500])
self.checkThermo(ctmlGas, yamlGas, [300, 400, 500], check_cp=False)

@utilities.slow_test
def test_Redlich_Kwong_ndodecane(self):
self.convert("nDodecane_Reitz", self.cantera_data_path)
ctmlGas, yamlGas = self.checkConversion('nDodecane_Reitz')
self.checkThermo(ctmlGas, yamlGas, [300, 400, 500])
self.checkThermo(ctmlGas, yamlGas, [300, 400, 500], check_cp=False)
self.checkKinetics(ctmlGas, yamlGas, [300, 500, 1300], [1e5, 2e6, 1.4e7],
1e-6)

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15 changes: 7 additions & 8 deletions src/thermo/RedlichKwongMFTP.cpp
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Expand Up @@ -337,14 +337,13 @@ void RedlichKwongMFTP::getPartialMolarEntropies(doublereal* sbar) const

void RedlichKwongMFTP::getPartialMolarIntEnergies(doublereal* ubar) const
{
getIntEnergy_RT(ubar);
scale(ubar, ubar+m_kk, ubar, RT());
}

void RedlichKwongMFTP::getPartialMolarCp(doublereal* cpbar) const
{
getCp_R(cpbar);
scale(cpbar, cpbar+m_kk, cpbar, GasConstant);
// u_k = h_k - P * v_k
getPartialMolarVolumes(m_partialMolarVolumes.data());
getPartialMolarEnthalpies(ubar);
double p = pressure();
for (size_t k = 0; k < nSpecies(); k++) {
ubar[k] -= p * m_partialMolarVolumes[k];
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Nice! I was fearing some long derivation on which I'd have to go and run due diligence to check 😂

}
}

void RedlichKwongMFTP::getPartialMolarVolumes(doublereal* vbar) const
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18 changes: 18 additions & 0 deletions test/thermo/RedlichKwongMFTP_Test.cpp
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Expand Up @@ -204,4 +204,22 @@ TEST_F(RedlichKwongMFTP_Test, localCritProperties)
EXPECT_NEAR(test_phase->critPressure(), 22.064e6, 1e-4);
}

TEST_F(RedlichKwongMFTP_Test, partialMolarIntEnergy)
{
// Check that sum(X_k * u) = u
set_r(0.4);
test_phase->setState_TP(400, 1.3e7);
double u_ref = test_phase->intEnergy_mole();
size_t kk = test_phase->nSpecies();
vector_fp uk(kk);
vector_fp X(kk);
test_phase->getMoleFractions(X.data());
test_phase->getPartialMolarIntEnergies(uk.data());
double u_test = 0;
for (size_t k = 0; k < kk; k++) {
u_test += uk[k] * X[k];
}
EXPECT_NEAR(u_ref, u_test, 1e-13 * std::abs(u_ref));
}

};