Reynolds Demo
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Transcript of Reynolds Demo
TOPIC 6: OSBORNE REYNOLDS DEMONSTRATION
6.1 THEORY
The theory is named in honour of Osborne Reynolds, a British engineer who
discovers the variables that can be used as a criterion to distinguish between
laminar and turbulent flow.
The Reynolds number is widely used dimensionless parameters in fluid
mechanics.
Reynolds number formula:
R = VLv
Where; R = Reynolds number
V = Fluid velocity (m/s)
L = characteristic length or diameter (m)
v = Kinematic viscosity (m2/s)
Reynolds number R is independent of pressure, P.
6.2 APPARATUS:
The Osborne Reynolds Demonstration apparatus is equipped with a
visualization tube for students to observe the flow condition. The rock inside the
stilling tank are to calm the inflow water so that there will not be any turbulence to
interfere with the experiment. The water inlet/outlet valve and dye injector are
utilized to generate the required flow.
1 Dye reservoir 2 Dye injector
3 Stilling tank 4 Observation tube
5 Water inlet valve 6 Bell mouth
7 Water outlet valve 8 Overflow tube
6.3 MAINTENANCE AND SAFETY PRECAUTIONS
1. Place the unit on a level ground.
2. Beware with the observation tube.
6.4 EXPERIMENTAL PROCEDURES
6.4.1 Experiment 1: Observation of Flow Regimes
Objective
To compute Reynolds number and to observe the laminar, transitional and
turbulent flow.
Procedures
1. The dye injector is lowered until it is seen in the glass tube.
2. The inlet valve is opened and water is allowed to enter the stilling tank.
3. A small overflow spillage through the over flow tube is ensured to
maintain a constant level.
4. The flow control valve is opened fractionally to let water flow through
the visualizing tube.
5. The dye control needle valve is slowly adjusted until a slow flow with
dye injection is achieved.
6. The water inlet and outlet valve are regulated until an identifiable dye
line is achieved. The type of the flow is identified and the picture of
the flow is taken.
7. The flow rate is measured.
8. The experiment is repeated to produce a few different types of flow.
9. The development of different flow in pipe is discussed.
6.4.2 Experiment 2: Loss Coefficient
Objective
To determine the Reynolds number and to determine the upper and lower
critical velocities at transitional flow.
Procedures
1. The dye injector is lowered until it is seen in the glass tube.
2. The inlet valve is opened and water is allowed to enter stilling tank.
3. A small overflow spillage through the over flow tube is ensured to
maintain a constant level.
4. Water is allowed to settle for a few minutes.
5. The flow control valve is opened fractionally to let water flow through
the visualizing tube.
6. The dye control needle valve is slowly adjusted until flow with dye
injection is achieved.
7. Small disturbance or eddied are produced to determine the lower
critical velocity.
8. The experiment is repeated by first introducing a turbulent flow and
produce the laminar flow to determine the upper critical velocity.
9. The findings from the results are summarized.
B) RESULTS, DISCUSSION, CONCLUSION, OPEN ENDED QUESTIONS,
REFERENCES
Name: Mohammad Iskandar Zulkarnain b. Roslan Matric No. : 42188
7. RESULTS
7.1 Experiment 1: Observation of Flow Regimes
Volume of water: 1L = 1 x 10-3 m3/s
Temperature = 270C
Diameter of the observation tube, D = 15.6 x10-3 m
Area of the observation tube, A = π4
D2
= 1.9113 x 10-4 m2
Flow t1 (s) t2 (s) t3 (s)
average
t (s)
Flow
rate, Q
(m3/s)
Laminar 119 80 72 90.33 1.1070 x
10-5
Transitio
n
62 60 63 61.67 1.6216 x
10-5
Turbulent 43 46 47 45.33 2.2059 x
10-5
SAMPLE CALCULATIONS
Volume flow rate, Q = Volume / time
For laminar flow,
Q = 1L / 90.33s
= 1.1070 x 10-5 m3/s
OBSERVATIONS
Laminar flow Transition flow
Turbulent flow
7.2 Experiment 2: Loss Coefficient
Forward (Laminar to Transition to Turbulent)
Flow
t1 (s) t2 (s) t3 (s) average
t (s)
Flow
rate, Q
(m3/s)
Fluid
velocity,
V (m/s)
Reynolds
number
Laminar 119 80 72 90.33 1.1070
x 10-5
0.05792 1058.02
Transitional 62 60 63 61.67 1.6216
x 10-5
0.08484 1549.77
Turbulent 43 46 47 45.33 2.2059
x 10-5
0.11541 2108.19
Backward (Turbulent to Transition to Laminar)
Flow t1 (s) t2 (s) t3 (s)
average
t (s)
Flow
rate, Q
(m3/s)
Fluid
velocity,
V (m/s)
Reynolds
number
Turbulent 44 46 47 45.67 2.1896
x 10-5
0.11456 2092.67
Transitional 64 60 63 62.33 1.6044
x 10-5
0.08394 1533.33
Laminar 80 72 72 74.67 1.3392
x 10-5
0.07007 1279.97
SAMPLE CALCULATIONS
Kinematic viscosity, v of water at 27oC = 8.54 x 10-7 m2/s
1. Forward
Laminar flow:
Velocity, V = Q/A
= (1.1070 x 10-5) / (1.9113 x 10-4 m2)
= 0.05792 m/s
Reynolds number, Re = VDv
= 0.05792 x 15.6E-3
8.54E-7
= 1058.02
2. Backward
Turbulent flow:
Velocity, V = Q/A
= (2.1896 x 10-5) / (1.9113 x 10-4 m2)
= 0.11456 m/s
Reynolds number, Re = VDv
= 0.11456 x15.6E-3
8.54E-7
= 2092.67
To determine upper and lower critical velocities,
1. Forward
Lower boundary
V = Q/A
= [1.6216 x 10-5] / [1.911 x 10-4]
= 0.08484 m/s
Upper boundary
V = Q/A
= [2.2059 x 10-5] / [1.911 x 10-4]
= 0.11541 m/s
2. Backward
Lower boundary
V = Q/A
= [1.6044 x 10-5] / [1.911 x 10-4]
= 0.08394 m/s
Upper boundary
V = Q/A
= [1.3392 x 10-5] / [1.911 x 10-4]
= 0.07007 m/s
Flow Upper boundary (m/s) Lower boundary (m/s)
Forward 0.11541 0.08484
Backward 0.07007 0.08394