3.1. Finding Area and Wetted Perimeter

Try these first

1. 1.

   What is the formula to calculate the area of a trapezoidal channel?

   Hint

   Think about the shapes involved in a trapezoid.

2. 2.

   Define wetted perimeter.

   Hint

   Consider what boundaries are touched by the liquid in an open channel.

3. 3.

   What formula represents the hydraulic radius?

   Hint

   Remember the relationship between area and wetted perimeter.

4. 4.

   True or False: The wetted perimeter only includes the bottom width of a trapezoidal channel.

   Hint

   Think about the dimensions of the full channel.

5. 5.

   A trapezoidal channel has a bottom width of 8 meters and side slopes of 2:1. Given a flow depth of 2.5 meters, calculate the area, wetted perimeter, and discharge using Manning's equation.

   Hint

   Pay attention to depth and slope when calculating.

6. 6.

   A circular pipe has a diameter of 1.2 meters and is flowing at a depth of 0.4 meters. Derive the area of flow, wetted perimeter, and evaluate the discharge rate. What if the diameter were reduced by half?

   Hint

   Use trigonometric relationships for the circular portion.