Object: To investigate relation between head over sill of a rectangular notch and the flow rate through the notch.
Here, you will learn about:
- Notches, flow rate, and cd.
- Experimental and graphical procedure of finding the relationship between head and discharge.
Apparatus Required:
Hydraulic Bench with (orifice and) notch apparatus, measuring cylinder, and stop-watch.

Arrangement of apparatus for measuring flow through Rectangular Notch
Theory:
Q C Td
x 2 / 3 xL
x H 3 / 2
(5.1)
where = Vol. of water collected
2g
T = Time in which is collected Q = Actual discharge
Cd = Coeff. of discharge for the notch L = Length of the notch
H = Head over the notch
Cd 2
1
L
3
. Qac H 3 / 2
(5.2)
Cd
2g
orC
0.033
L
0.011
Qac H 3 / 2
Qac
(cgsunits)
if L 3
(cgs mits)
(5.3)
(5.4)
dH 3 / 2
Procedure:
Observations:
Length of the notch, L = 3cm
S. No | H (cm) | H3/2 (cm3/2) | Qac | C 0.011 Qac dH 3 / 2 | ||
(cm3) | T (sec) | Qac= /T (cm3/ sec) | ||||
1 2 3 4 | Mean | |||||
… |

Results & Comments: