# How do you calculate water flow over a weir?

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## How do you calculate water flow over a weir?

The equation recommended by the Bureau of Reclamation in their Water Measurement Manual, for use with a suppressed rectangular weir is: Q = 3.33 B H3/2, where Q is the water flow rate in ft3/sec, B is the length of the weir (and the channel width) in ft, and H is the head over the weir in ft.

What happens when the water flows approaching a weir?

As the liquid approaches the weir, the liquid level gradually drops and the flow velocity increases. Downstream from the weir, a jet is formed. This is called the nappe and it is ventilated underneath to enable it to spring free from the weir crest [Barna (1969)].

What are the limitations of the theory flow over weirs?

The empirical equation and discharge coefficients were found for the rectangular and V-shaped weir and compared with the literature and vendor values. The limitations of the theory is that it has to be level so the only force on the water is gravity, there has to be a constant flow, and constant pressure.

### What is the difference between weir and notch?

Basically there is no difference between a notch and a weir, except that a notch is of small size while a weir is of large size. A notch is usually made of metal plate whereas a weir is made of masonry or concrete. The bottom edge over which the water flows is called the sill or the crest of water the notch.

What is end contraction of weir?

An end contraction is when the length of the weir (L) is less than the width of the Channel and a nappe contracts either one or both sides of the weir. The effective length of the weir in SWMM 5 is: L = Original Length – Number of End Contractions * Head over the Weir.

Does the length of weir affect the discharge coefficient?

A comparison of the obtained results with the values of the discharge coefficient of the same BCW using the methods of Kumin and Hager indicates that this coefficient depends on both the height of the wall and the length of the weir.

## What is the point of a weir?

A weir is a small dam built across a body of water, such as a river. We use them to help control the flow of water. Weirs can help raise the water level so that boats can pass through, and they can also reduce the flow of water to prevent flooding.

What is meant by end contraction effect on notches and weirs?

An end contraction is when the length of the weir (L) is less than the width of the Channel and a nappe contracts either one or both sides of the weir.

How to determine the coefficient of discharge from a flow over Weir?

The coefficients of discharge are determined by measuring the height of the water surface above the notch base and the corresponding flow rate. The general features of the flow can be determined by direct observation. 5. Equipment The following equipment is required to perform the flow over weirs experiment: F1-13 rectangular and triangular weirs;

### Can a weir be used as a flow-measuring device?

Since there is a unique relationship between the critical depth and discharge, a weir can be designed as a flow-measuring device. Weirs are also built to raise the water level in a channel to divert the flow to irrigation systems that are located at higher elevations. 3. Objective The objectives of this experiment are to:

Who are the instructors of the flow over weirs experiment?

1Instructors : Dr. Khalil M. Alastal Eng. Mohammed Y. Mousa Experiment (6): Flow over weirs Introduction:

How does a weir work?

Since there is a unique relationship between the critical depth and discharge, a weir can be designed as a flow-measuring device. Weirs are also built to raise the water level in a channel to divert the flow to irrigation systems that are located at higher elevations. 3.

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