Added use of GridFunctions to an example (#59)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

CONTRIBUTORS.md

@@ -7,6 +7,7 @@
 ## Individual Contributors
 
 * [Alejandro Fernández Luces](https://github.com/AlejandroFernandezLuces)
+* [Augusto Finger Pacheco](https://github.com/fingeraugusto)
 * [Gustavo Corrêa Martins](https://github.com/gcmartins)
 * [Jorge Martínez Garrido](https://github.com/jorgepiloto)
 * [Roberto Pastor Muela](https://github.com/RobPasMue)

examples/basic_examples/particle_wall_interaction_with_motion.py

@@ -114,20 +114,38 @@
 times, mass_flow_in = particles.GetNumpyCurve("Particles Mass Flow In", unit="t/h")
 times, mass_flow_out = particles.GetNumpyCurve("Particles Mass Flow Out", unit="t/h")
 
+# Obtain the maximum and minimum velocities of the particles at each time step.
+import numpy as np
+
+simulation_times = study.GetTimeSet()
+velocity_gf = particles.GetGridFunction("Velocity : Translational : Absolute")
+velocity_max = np.array(
+    [velocity_gf.GetMax(unit="m/s", time_step=i) for i in range(len(simulation_times))]
+)
+velocity_min = np.array(
+    [velocity_gf.GetMin(unit="m/s", time_step=i) for i in range(len(simulation_times))]
+)
+
 
 #################################################################################
 # Plot curves
 # +++++++++++
 
 import matplotlib.pyplot as plt
 
-fig, ax = plt.subplots(1)
+fig, (ax1, ax2) = plt.subplots(2, 1)
+
+ax1.plot(times, mass_flow_in, "b", label="Mass Flow In")
+ax1.plot(times, mass_flow_out, "r", label="Mass Flow Out")
+ax1.set_xlabel("Time [s]")
+ax1.set_ylabel("Mass Flow [t/h]")
+ax1.legend(loc="upper left")
 
-ax.plot(times, mass_flow_in, "b", label="Mass Flow In")
-ax.plot(times, mass_flow_out, "r", label="Mass Flow Out")
-ax.set_xlabel("Time [s]")
-ax.set_ylabel("Mass Flow [t/h]")
-ax.legend(loc="upper left")
+ax2.plot(simulation_times, velocity_max, "b", label="Max Velocity")
+ax2.plot(simulation_times, velocity_min, "r", label="Min Velocity")
+ax2.set_xlabel("Time [s]")
+ax2.set_ylabel("Velocity [m/s]")
+ax2.legend(loc="upper left")
 
 plt.draw()