To determine Cd of a venturi flume

Object: To determine the Cd of a venturi flume.

Apparatus Required:

• S-4 Tilting flume consisting of the tilt control device, rotameter, and Venturi flume plates.
  

Perspex-sided S4 tilting flume

Theory:

For a convergence – divergence flume,

Qth

 b

h H  h1 / 2

(6.1)

When the convergence is sufficiently narrow the flow in it passes through critical phase

2g

1

 h  2

3 H1 , and the discharge becomes related to H1 as:





 11 / 2

2g 2

3

Qth = b

H₁  3 H 

i.eQth = 1.705 b

orQth = 17.05 b



3/ 2

H

1

3/ 2

H

1



(mks units)(6.2)

(cgs units)(6.3)

Approximating H1 to H,

Qac = 17.05 Cd b

H3/2

(6.4)

orCd =

Qac

17.05b H^3/2

(cgs units)(6.5)

Procedure:

Observations:

b = 4.7 cm

Results & Comments: