The length of the perimeter in contact with the water. For a circular pipe of inside diameter “d”, flowing full, the wetted perimeter is the circumference, d. The same pipe flowing half full would have a wetted perimeter of d/2.
The length of the perimeter in contact with the water. For a circular pipe of inside diameter “d”, flowing full, the wetted perimeter is the circumference, d. The same pipe flowing half full would have a wetted perimeter of d/2.