From Fluids Wiki
Jump to: navigation, search
phase pendulum.jpg

The image on the right is the phase portrait for a simple pendulum. The horizontal axis is the angle of the pendulum and the vertical is the rate of change of the angle. Inside the eye-shaped black lines the dynamics are oscillations along the yellow lines. Outside the black lines we have the pendulum spinning left or right, not oscillating. The black lines form the separatrix for the system.