A presentation on orifice and mouthpiece. useful to understand basic concept.

1. A presentation
On
Fluid mechanics
Topic : orifices and mouthpieces
Mechanical Department

2. What is Orifice?
• Orifice is a small opening of cross-section on
the side at the bottom of a tank.
• Used for measuring the rate of flow of fluid.

3. Classification Orifice:
Orifice
1. Depending upon the size of orifice.
2. Depending upon their cross-sectional area.
3. Depending upon the shape of upstream edge.
4. Depending upon the nature of discharge.

4.  Applying Bernoulli's
equation at points 1 & 2,
 We get
𝑝1
𝜌𝑔
+
𝑣1
2
2𝑔
+𝑧1 =
𝑝2
𝜌𝑔
+
𝑣2
2
2𝑔
+𝑧2
But 𝑧1 = 𝑧2
so, 𝑝1
𝜌𝑔
+
𝑣1
2
2𝑔
= 𝑝2
𝜌𝑔
+
𝑣2
2
2𝑔
Flow through Orifice:

5. Now, 𝑝1
𝜌𝑔
=H and 𝑝2
𝜌𝑔
= 0 (atmospheric pressure)
Here, 𝑣1 is very small i.c.t. 𝑣2 .
So H + 0 = 0 +
𝑣2
2
2𝑔
𝑣2= 2𝑔𝐻
This is theoretical velocity.

6. HYDRAULIC CO-EFFICIENTS
• Co-efficient of velocity, Cv
• Co-efficient of contraction, Cc
• Co-efficient of discharge, Cd

7. Cv =
actual velocity of jet at vena−contracta
theoretical velocity
Cv =
𝑉
2𝑔𝐻
The value of Cv varies from 0.95 to 0.99 for different
orifices.
1. Co-efficient of Velocity, Cv

8. 2. Co-efficient of Contraction, Cc
Cc =
area of the jet at vena−contracta
area of the orifice
Cc =
𝑎𝑐
𝑎
The value of Cc varies from 0.61 to 0.69 for different
orifices.

9. 3. Co-efficient of Discharge, Cd
Cd =
𝑄
𝑄 𝑡ℎ
=
actual velocity ∗ actual area
theoretical velocity ∗ theoretical area
Cd = Cc* Cv
The value of Cd varies from 0.61 to 0.65 for different
orifices.

10. Thank You 