1D Weirs

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Introduction

A weir is a barrier across a designated flow path that is designed to alter flow characteristics. Most common weirs act as an obstruction, smaller but similar to a dam, that pools water behind it while allowing water to steadily flow over the top. Weirs within TUFLOW, like bridges, do not require data for length, Manning's n, divergence or bed slope so they are zero-length channels effectively.

Weir types that can be used within TUFLOW

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• Broad-crested weir

If the height of water above the weir crest is not greater than two times of the width of the crest of weir, the weir is called a Broad Crested weir.

• Crump weir

The Crump Weir models a triangular profile weir with a 1:2 sloping front face and a 1:5 sloping back face. This type of weir are used as measuring structures within open channel.

https://ecofactireland.files.wordpress.com/2014/04/lamprey-barrier.jpg

• Ogee-crested weir

An ogee-crested weir is a special type of weir, generally used as a spillway of a dam as shown in figure. The crest of an ogee weir slightly rises up from the inside edge (i.e., a slight hump on top of the weir) and after reaching the maximum rise of 0.115 H (where H is the height of the water above the inside edge) falls in a parabolic form over the edge of the weir.

http://www.ancold.org.au/wp-content/uploads/2014/08/Figure-2Harvey-Dam-Ogee-crest-over-flowing-for-the-first-time.jpg

• Rectangular weir

• Trapezoidal or Cippoletti weir

The "Cippoletti" weir is a trapezoidal shaped weir. The purpose of the slope, on the sides, is to obtain an increased discharge through the triangular portions of the weir, which otherwise would have been decreased due to end contractions in the case of rectangular weirs.

http://www.codecogs.com/library/engineering/fluid_mechanics/weirs/discharge.php

• V-notch weir

• Spillway

Bath, UK (pht: Rohan King)

Irregular shaped weirs

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Operational Control

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Typical check files used

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Any further questions please email TUFLOW support: support@tuflow.com

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