What is wetted perimeter?

The wetted perimeter is the length of the perimeter of a cross-sectional area of a channel that is in contact with water. It is an important factor in determining the hydraulic radius, which is used in various hydraulic calculations.

The wetted perimeter can vary depending on the shape of the channel or pipe, with different shapes having different wetted perimeters. For example, a circular pipe will have a smaller wetted perimeter compared to a rectangular channel of the same cross-sectional area.

The wetted perimeter is used in calculations related to flow velocity, flow resistance, and flow capacity of channels and pipes. It is also important in determining the friction factor, which is used in calculating head loss in pipes and channels.

In general, minimizing the wetted perimeter can help reduce frictional losses and improve the flow capacity of a channel or pipe. This can be achieved by using shapes with smaller wetted perimeters, maintaining smooth surfaces, and keeping the water level as close to the top of the channel or pipe as possible.