Piezoelectric Wind Energy Harvesting from Self-Excited Vibration of Square Cylinder

Figure 6

Vorticity contours of the vortex street: (a) the original position of the cylinder; (b) the cylinder moving to the top position in the flow; (c) the cylinder moving back to the original position; (d) the cylinder moving to the bottom position in the flow.

(a)

(b)

(c)

(d)