[1D] Provide reasonable default grid for CounterflowDiffusionFlame

doc/sphinx/cython/onedim.rst

@@ -21,7 +21,7 @@ BurnerFlame
 
 CounterflowDiffusionFlame
 ^^^^^^^^^^^^^^^^^^^^^^^^^
-.. autoclass:: CounterflowDiffusionFlame(gas, grid=None)
+.. autoclass:: CounterflowDiffusionFlame(gas, grid=None, width=None)
 
 CounterflowPremixedFlame
 ^^^^^^^^^^^^^^^^^^^^^^^^

interfaces/cython/cantera/examples/onedim/diffusion_flame.py

@@ -16,9 +16,7 @@ mdot_f = 0.24  # kg/m^2/s
 comp_o = 'O2:0.21, N2:0.78, AR:0.01'  # air composition
 comp_f = 'C2H6:1'  # fuel composition
 
-# Distance between inlets is 2 cm.
-# Start with an evenly-spaced 6-point grid.
-initial_grid = np.linspace(0, 0.02, 6)
+width = 0.02 # Distance between inlets is 2 cm
 
 tol_ss = [1.0e-5, 1.0e-12]  # [rtol, atol] for steady-state problem
 tol_ts = [5.0e-4, 1.0e-11]  # [rtol, atol] for time stepping
@@ -34,7 +32,7 @@ gas.TP = gas.T, p
 # Create an object representing the counterflow flame configuration,
 # which consists of a fuel inlet on the left, the flow in the middle,
 # and the oxidizer inlet on the right.
-f = ct.CounterflowDiffusionFlame(gas, initial_grid)
+f = ct.CounterflowDiffusionFlame(gas, width=width)
 
 # Set the state of the two inlets
 f.fuel_inlet.mdot = mdot_f

interfaces/cython/cantera/examples/onedim/diffusion_flame_batch.py

@@ -36,11 +36,10 @@ refine = True
 # Set up an initial hydrogen-oxygen counterflow flame at 1 bar and low strain
 # rate (maximum axial velocity gradient = 2414 1/s)
 
-# Initial grid: 18mm wide, 21 points
 reaction_mechanism = 'h2o2.xml'
 gas = ct.Solution(reaction_mechanism)
-initial_grid = np.linspace(0.0, 18e-3, 21)
-f = ct.CounterflowDiffusionFlame(gas, initial_grid)
+width = 18e-3 # 18mm wide
+f = ct.CounterflowDiffusionFlame(gas, width=width)
 
 # Define the operating pressure and boundary conditions
 f.P = 1.e5  # 1 bar

interfaces/cython/cantera/examples/onedim/diffusion_flame_extinction.py

@@ -29,11 +29,10 @@ if not os.path.exists(data_directory):
 # Set up an initial hydrogen-oxygen counterflow flame at 1 bar and low strain
 # rate (maximum axial velocity gradient = 2414 1/s)
 
-# Initial grid: 18mm wide, 21 points
 reaction_mechanism = 'h2o2.xml'
 gas = ct.Solution(reaction_mechanism)
-initial_grid = np.linspace(0.0, 18.e-3, 21)
-f = ct.CounterflowDiffusionFlame(gas, initial_grid)
+width = 18.e-3 # 18mm wide
+f = ct.CounterflowDiffusionFlame(gas, width=width)
 
 # Define the operating pressure and boundary conditions
 f.P = 1.e5  # 1 bar

interfaces/cython/cantera/onedim.py

@@ -506,13 +506,18 @@ class CounterflowDiffusionFlame(FlameBase):
     """ A counterflow diffusion flame """
     __slots__ = ('fuel_inlet', 'flame', 'oxidizer_inlet')
 
-    def __init__(self, gas, grid=None):
+    def __init__(self, gas, grid=None, width=None):
         """
         :param gas:
             `Solution` (using the IdealGas thermodynamic model) used to
             evaluate all gas properties and reaction rates.
         :param grid:
-            Array of initial grid points
+            A list of points to be used as the initial grid. Not recommended
+            unless solving only on a fixed grid; Use the `width` parameter
+            instead.
+        :param width:
+            Defines a grid on the interval [0, width] with internal points
+            determined automatically by the solver.
 
         A domain of class `AxisymmetricStagnationFlow` named ``flame`` will
         be created to represent the flame. The three domains comprising the
@@ -527,6 +532,9 @@ class CounterflowDiffusionFlame(FlameBase):
 
         self.flame = AxisymmetricStagnationFlow(gas, name='flame')
 
+        if width is not None:
+            grid = np.array([0.0, 0.2, 0.4, 0.6, 0.8, 1.0]) * width
+
         super(CounterflowDiffusionFlame, self).__init__(
                 (self.fuel_inlet, self.flame, self.oxidizer_inlet), gas, grid)
 

interfaces/cython/cantera/test/test_onedim.py

@@ -387,7 +387,7 @@ class TestDiffusionFlame(utilities.CanteraTest):
     def create_sim(self, p, fuel='H2:1.0, AR:1.0', T_fuel=300, mdot_fuel=0.24,
                    oxidizer='O2:0.2, AR:0.8', T_ox=300, mdot_ox=0.72):
 
-        initial_grid = np.linspace(0, 0.02, 6)  # m
+        width = 0.02 # m
         tol_ss = [2.0e-5, 1.0e-11]  # [rtol, atol] for steady-state problem
         tol_ts = [5.0e-4, 1.0e-11]  # [rtol, atol] for time stepping
 
@@ -396,7 +396,7 @@ class TestDiffusionFlame(utilities.CanteraTest):
         self.gas.TP = T_fuel, p
 
         # Flame object
-        self.sim = ct.CounterflowDiffusionFlame(self.gas, initial_grid)
+        self.sim = ct.CounterflowDiffusionFlame(self.gas, width=width)
         self.sim.flame.set_steady_tolerances(default=tol_ss)
         self.sim.flame.set_transient_tolerances(default=tol_ts)