NOTCHES AND WEIR

 

 NOTCH ,WEIR AND ITS TYPES

Notch

A notch may be defined as an obstruction over which the flow of liquid occurs

 In case of measuring tank or reservoir, the opening is provided at the side of the tank such that the liquid surface in the tank is below the top edge of the opening. Weir

A weir is a notch on a large scale used for measuring the flow of a river, canal etc. It is a concrete or masonry structure of substantial breadth built across the river in the direction of flow. This allows the excess water to flow over its entire length to the downstream side. Thus a weir is similar to a small dam constructed across the river, with a difference that the excess water flows downstream only through a small portion called spillway and in case of weir, the excess water flows over its entire length.

Nappe and crest

The sheet of water flowing through a notch or over a weir is known as nappe or vein. The bottom edge of the notch or the top of a weir over which water flows is known as sill or crest. The height above the bottom of the tank or channel is known as crest height.

 

Nappe and crest

Difference between orifice and notch

Orifice

Notch

An orifice may be defined as an opening provided in the side or bottom of tank or vessel such that the liquid flows through the entire orifice.

 


 

A notch may be defined as an opening provided in the side of tank or vessel such that the liquid surface in tank is below the top edge of opening.

  



 

 

Difference between notches and weirs

 

Notch

Weir

A notch may be defined as an opening provided in the side of tank or vessel such that the liquid surface in tank is below the top edge of opening.

 

A weir may be defined as any regular obstruction in open stream over which the flow takes place.

 

Small structure

Large structure

Made of metallic plates.

Made of concrete/bricks.

Measure small flow rate.

Measure large flow rate.

 

 Types of Weir

1.      Shape

�         Rectangular

�         Triangular

�         Trapezoidal



GO THROUGHNTHE VIDEO LINK FOR ANY CLARIFICATION: 

1.https://youtu.be/hjSaSkto7_c

2.https://youtu.be/Rwl1mu0TJmE

3.https://youtu.be/1wibPsHrzb0

 


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