Open Channel Flow Calculator

Water can be transported using one of two methods: pressure or gravity. We could use a big water pump to bring water up a building. The water pump would propel the water up the pipes by exerting a high amount of pressure on it via mechanical action, most commonly centrifugal force. As water moves upwards, it will fill the pipes. This is referred to as a closed channel since the pipe cross-section is completely enclosed and not exposed to air pressure.

When water flows from an upper to the lower elevation and the water surface is "open" or exposed to air pressure, we call it an open channel flow. Examples include rivers and canals. Water may flow due to gravity in some cases, but the channel or pipe may be full. 

We consider steady and uniform flow in this open channel flow calculator. The flow rate does not fluctuate in a channel with a constant cross-sectional shape, slope, or roughness in a steady uniform flow. As long as we have all of the other properties of the channel, we can compute the dimensions of the chosen uniform shape in this type of flow.

Manning's formula is as follows, with these considerations in mind: V = (1 / n) * R^2/3 * s1/2

• Where V - Velocity or mass flow rate of water
• n - Manning's roughness coefficient
• R - Hydraulic radius
• s - Slope of the channel

We can see from Manning's equation that the area and slope are directly proportional to the water flow rate, hence increasing the area and slope will increase the water flow rate. The roughness coefficient and the wetted perimeter are inversely proportional to the water flow rate, which means that raising their values reduces the water flow rate.

Aside from this flow rate, the volumetric flow rate, which is just the product of the mass flow rate and the cross-sectional area, can also be considered, as illustrated below: Q = V * A

• Where, Q - Volumetric flow rate
• V - Mass flow rate
• A - Cross-sectional area 

For custom-sized channel designs and the most cost-effective cross-sections, utilize our open channel flow calculator to calculate the water flow rate. You can input your chosen values for the channel dimensions when utilizing the custom design option in the design field. The water flow's cross-sectional area, as well as the channel's wetted perimeter, mass flow rate, hydraulic radius, and volumetric flow rate, will be calculated by the calculator.

When choosing the most efficient design choice, on the other hand, you can just input the water flow depth. You will view the results after selecting the channel surface roughness coefficient and entering a channel slope. We calculated efficient and affordable open-channel designs using the constants of a most efficient cross-section of the open channels.

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1. What is Manning's formula?

The Manning formula is an empirical method for calculating the average velocity of a liquid flowing through a conduit that does not entirely enclose the liquid, known as open channel flow.

2. What does R stand for in the Manning formula?

The hydraulic radius, R, is measured in feet. This is the variable that accounts for the channel shape in the equation. The hydraulic radius is calculated by dividing the flow's area by its wetted perimeter.

3. How can you find out how much water is in the channel?

The DCM is built around the area's uniform velocity. The main channel and floodplains are separated from the compound channel section in this method, and the total flow is computed by adding the discharge through the area.

4. Which channel is most effective?

When the discharge carrying capacity for a particular cross-section area is at its greatest, a section is said to be most efficient. The lining is the most expensive component of the entire building cost, and if the perimeter is kept to a minimum, the cost of lining will be minimal, making it the most cost-effective segment.

5. Is Manning's formula consistent in terms of dimensions?

The Chezy and Manning equations, which are at the heart of our current open channel hydraulics knowledge, are not dimensionally homogeneous. The author proposes a new derivation of these equations that reveals the individual elements of these coefficients, enabling more precise values to be calculated.