# How to calculate the wetted perimeter

• theBEAST
In summary, the wetted perimeter is the total length of the surface of a body of water that is in contact with the bed or banks. It is important to calculate it for determining flow rate and for engineering projects. The formula for a rectangular channel is 2*(width + height), and for a triangular channel it is (base length/2) + (height of the triangle * 2). Factors such as shape and roughness of the channel can also affect the wetted perimeter.
theBEAST

## Homework Statement

So I have been taught that the wetted perimeter is the perimeter in which the surface is wet. So in the case for internal forced convection of a thick wall pipe I would have thought the perimeter would be 2*pi*r where r is the inner radius of the pipe. However, doing a bit of googling, this answer is clearly wrong as shown in the image below:

Does anyone know why?

Yes. This is not a thick walled pipe calculation. It is a calculation of axial flow along an annular channel (between two concentric cylinders).

Chet

## What is the wetted perimeter?

The wetted perimeter is the total length of the surface of a body of water that is in contact with the bed or banks of the water body.

## Why is it important to calculate the wetted perimeter?

Calculating the wetted perimeter is important for determining the flow rate of a body of water, which is crucial for understanding and managing water resources. It is also used in engineering projects such as designing canals, culverts, and bridges.

## How do you calculate the wetted perimeter of a rectangular channel?

The wetted perimeter of a rectangular channel is equal to the sum of the width and height of the channel. So, the formula for calculating the wetted perimeter is 2*(width + height).

## What is the formula for calculating the wetted perimeter of a triangular channel?

The formula for calculating the wetted perimeter of a triangular channel is (base length/2) + (height of the triangle * 2). This formula takes into account the hypotenuse of the triangle as well as the two sides that make up the base.

## Are there any other factors to consider when calculating the wetted perimeter?

Yes, the shape and roughness of the channel can also affect the wetted perimeter. For example, a channel with a rougher surface will have a larger wetted perimeter compared to a smooth channel of the same dimensions.

Replies
63
Views
3K
Replies
8
Views
2K
Replies
43
Views
3K
Replies
3
Views
654
Replies
7
Views
2K
Replies
8
Views
4K
Replies
18
Views
5K
Replies
4
Views
2K
Replies
3
Views
981
Replies
4
Views
961