[Cython] Added molar_fluxes method to DustyGasTransport

interfaces/cython/cantera/_cantera.pxd

@@ -184,6 +184,7 @@ cdef extern from "cantera/transport/DustyGasTransport.h" namespace "Cantera":
         void setMeanPoreRadius(double) except +
         void setMeanParticleDiameter(double) except +
         void setPermeability(double) except +
+        void getMolarFluxes(double*, double*, double, double*) except +
 
 
 cdef extern from "cantera/equil/MultiPhase.h" namespace "Cantera":

interfaces/cython/cantera/test/test_transport.py

@@ -47,6 +47,7 @@ class TestTransport(utilities.CanteraTest):
 class TestDustyGas(utilities.CanteraTest):
     def setUp(self):
         self.phase = ct.DustyGas('h2o2.xml')
+        self.phase.TPX = 500.0, ct.one_atm, "O2:2.0, H2:1.0, H2O:1.0"
         self.phase.porosity = 0.2
         self.phase.tortuosity = 0.3
         self.phase.mean_pore_radius = 1e-4
@@ -65,3 +66,21 @@ class TestDustyGas(utilities.CanteraTest):
 
     # The other parameters don't have such simple relationships to the diffusion
     # coefficients, so we can't test them as easily
+
+    def test_molar_fluxes(self):
+        T1, rho1, Y1 = self.phase.TDY
+        self.phase.TPX = 500.0, ct.one_atm, "O2:2.0, H2:1.001, H2O:0.999"
+
+        T2, rho2, Y2 = self.phase.TDY
+
+        fluxes0 = self.phase.molar_fluxes(T1, T1, rho1, rho1, Y1, Y1, 1e-4)
+        self.assertArrayNear(fluxes0, np.zeros(self.phase.n_species))
+
+        fluxes1 = self.phase.molar_fluxes(T1, T2, rho1, rho2, Y1, Y2, 1e-4)
+        kH2 = self.phase.species_index('H2')
+        kH2O = self.phase.species_index('H2O')
+        self.assertTrue(fluxes1[kH2] < 0)
+        self.assertTrue(fluxes1[kH2O] > 0)
+
+        # Not sure why the following condition is not satisfied:
+        # self.assertNear(sum(fluxes1) / sum(abs(fluxes1)), 0.0)

interfaces/cython/cantera/transport.pyx

@@ -135,3 +135,39 @@ cdef class DustyGasTransport(Transport):
         """Permeability of the porous medium [m^2]."""
         def __set__(self, value):
             (<CxxDustyGasTransport*>self.transport).setPermeability(value)
+
+    def molar_fluxes(self, T1, T2, rho1, rho2, Y1, Y2, delta):
+        """
+        Get the molar fluxes [kmol/m^2/s], given the thermodynamic state at
+        two nearby points.
+
+        :param T1:
+            Temperature [K] at the first point
+        :param T2:
+            Temperature [K] at the second point
+        :param rho1:
+            Density [kg/m^3] at the first point
+        :param rho2:
+            Density [kg/m^3] at the second point
+        :param Y1:
+            Array of mass fractions at the first point. Length `n_species`.
+        :param Y2:
+            Array of mass fractions at the second point. Length `n_species`.
+        :param delta:
+            Distance [m] between the two points.
+        """
+
+        cdef np.ndarray[np.double_t, ndim=1] state1 = np.empty(self.n_species + 2)
+        cdef np.ndarray[np.double_t, ndim=1] state2 = np.empty(self.n_species + 2)
+        cdef np.ndarray[np.double_t, ndim=1] fluxes = np.empty(self.n_species)
+
+        state1[0] = T1
+        state1[1] = rho1
+        state1[2:] = Y1
+        state2[0] = T2
+        state2[1] = rho2
+        state2[2:] = Y2
+
+        (<CxxDustyGasTransport*>self.transport).getMolarFluxes(&state1[0],
+            &state2[0], delta, &fluxes[0])
+        return fluxes