[Python/Examples] Added option to plot results for premixed twin flame

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

@@ -8,6 +8,7 @@ latter simulates a jet of reactants shooting into products.
 
 import cantera as ct
 import numpy as np
+import sys
 
 # Differentiation function for data that has variable grid spacing Used here to
 # compute normal strain-rate
@@ -112,3 +113,39 @@ print("Peak temperature: {0:.1f} K".format(T))
 print("Strain Rate: {0:.1f} 1/s".format(K))
 print("Consumption Speed: {0:.2f} cm/s".format(Sc*100))
 oppFlame.write_csv("premixed_twin_flame.csv", quiet=False)
+
+# Generate plots to see results, if user desires
+if '--plot' in sys.argv:
+
+    import matplotlib.pyplot as plt
+
+    plt.figure(figsize=(8,6), facecolor='white')
+
+    # Axial Velocity Plot
+    plt.subplot(1,2,1)
+    plt.plot(oppFlame.grid, oppFlame.u, 'r', lw=2)
+    plt.xlim(oppFlame.grid[0], oppFlame.grid[-1])
+    plt.xlabel('Distance (m)')
+    plt.ylabel('Axial Velocity (m/s)')
+
+    # Identify the point where the strain rate is calculated
+    plt.plot(oppFlame.grid[strainRatePoint], oppFlame.u[strainRatePoint],'gs')
+    plt.annotate('Strain-Rate point',
+                 xy=(oppFlame.grid[strainRatePoint], oppFlame.u[strainRatePoint]),
+                 xytext=(0.001, 0.1),
+                 arrowprops={'arrowstyle':'->'})
+
+    # Temperature Plot
+    plt.subplot(1,2,2)
+    plt.plot(oppFlame.grid, oppFlame.T, 'b', lw=2)
+    plt.xlim(oppFlame.grid[0], oppFlame.grid[-1])
+    plt.xlabel('Distance (m)')
+    plt.ylabel('Temperature (K)')
+
+    plt.tight_layout()
+    plt.show()
+
+else:
+    print('************')
+    print('Plotting option not enabled. Re-run script with --plot to see key plots.')
+    print('************')