Notch and Weir, definition, classification, types, difference.

Notch:-

• A notch is an opening in the side of a tank or a vessel in such away that the liquid surface is below the top edge of the opening. 
• In other words, it is a device used to measure the rate of a liquid through a tank or a small channel. 
• Mitch is a very thin structure, usually made of a metallic plate. 

Weir:-

• A weir I'd an obstruction constructed over the channel, which causes the upstream level to rise until the flow across. 
• In other words, a weir is a concrete or masonry structure across a stream or an open channel over which the liquid flow across. 
• A weir is a notch on a large scale. 
• It has a substantial breadth in the direction of flow. 

* The terms related to notch and weir are:-

Nappe or Vein:-

                                The sheet of water flowing through a notch or weir is known as nappe or vein. 

Crest or Sill:-

                            The bottom edge of a notch or the top edge of a weir over a which water flows is known as Crest or sill. 

☆ Classification of Notches and Weirs:-

1. Notches:-

                         Notches are classified as:-

i. On the basis of their shape of opening:-

a. Rectangular notch

b. Triangular notch ( V- Notch)

c. Trapezoidal notch

d. Stepped notch.

ii. On the basis of effect of the sides of notch on the napple:-

a. Notch with end contraction. 

b. Suppressed notch that is Notch without abby end contraction.

Must read:- Measurement of pressure, Absolute, Atmospheric and vaccum gauge.

2. Weirs:-

                  Weir's are classified as:-

i. On ther basis of shape:-

a. Rectangular weir

b. Triangular weir

c. Trapezoidal weir

ii. On the basis of shape of Crest:-

a. Narrow crested weir

b. Broad crested weir

c. Sharp crested weir

d. Ogee shaped weir

iii. On the basis of effect of sides of weir on               the nappel:-

a. Contacted weir 

b. Suppressed weir 

iv. On the basis of discharge condition:-

a. Ordinary weir

b. Drowned or submerged weir.