This document summarizes the calibration of a subsonic wind tunnel. Calibration establishes the reliability and accuracy of measurements by comparing the wind tunnel's measurements to a standard. The specifications of the wind tunnel are provided, including a test section size of 600x600x2000 mm and maximum test section velocity of 50 m/s. The calibration procedure involves using a pitot tube connected to a manometer to measure total and static pressure at different fan speeds. These measurements are used to calculate flow velocity and plot a calibration chart comparing flow velocity to motor speed with less than 3% error.

1. Calibration of sub sonic wind
tunnel
By
ABHIJEET (1SJ17AE002)
AKASH (1SJ17AE004)
AKSHATA (1SJ17AE005)
AMRUTHA( 1SJ17AE006)
Jai shree gurudev

2. CALIBRATION
• CALIBRATION is a documented comparison of the measurement device
to be calibrated against a traceable reference standard or device
Need of calibration:
Making sure that instrument making consistent measurement and
displaying the correct readings
Establishing the instruments reliability
Maintaining adherence to industry standards , govt regulations ,
quality assurance norms like current good manufacturing practice
Determining the precision , deviation , and reliability of
measurements

3. WIND TUNNEL
Wind tunnels are large tubes with air blowing
through them
Need of wind tunnel:
tunnels are used to replicate the actions
of an object flying through the air or moving
along the ground
researchers use wind tunnels to learn
more about how aircraft will fly
the wind tunnel moves air around an
object making it seem as if the object is really
flying

4. Specifications of wind tunnel
• Type :low speed , subsonic , open circuit , suction type
• Contraction ratio : 9:1
• Test section size : 600*600*2000 mm
• Test section velocity : 50 m/s
• Velocity measurement : Pitot tube with digital indicator
• Speed measurement : Digital speed indicator with proximity sensor
• Fan type : Axial flow type
• No of blades : 18
• Motor capacity : 20 HP
• Power requirement : AC 3 phase , 440 volts , 32 amps ,with earth & neutral
connection

5. Pitot tube

6. Procedure
• Check the wind tunnel for any loose parts
• Check the level manometer liquid in multi manometer
• Connect the total and static pressure port of the pitot static tube to the
manometer tubes for measuring the total and static pressure
• Note down the initial reading in the manometer
• Run the tunnel at different speeds and note down the manometer reading
from the air velocity indicator
• Gradually shut down the wind tunnel
• Calculate the air velocity by using formula
• Draw the calibration chart between flow velocity and motor speed

7. Formulae:

8. TABULAR COLUMN
Serial no Speed (rpm) Actual
velocity Va
(m/s)
Manometer
differential
height Δh
(m)(10^-3)
Flow velocity
Vc=129.7√Δh
(m/s)
Frequency
(Hz)
% Error
=
((Va-Vc)/Va)*100
1 400 12.6 9.6 12.70 13.56 2.1
2 600 19.8 22.3 19.36 20.28 2.102
3 800 26.5 40.1 25.97 26.95 2.0
4 1000 33.3 63.2 32.60 33.7 2.2
5 1200 40 91.2 39.16 40.56 0.793

9. Calibration chart bw flow velocity & motor
speed
0
5
10
15
20
25
30
35
40
45
0 200 400 600 800 1000 1200 1400
Y-Values
Speed (rpm)
F
L
O
W
V
E
L
O
C
I
T
y