EXPERIMENT NO. 4:
REYNOLD’S NUMBER: LAMINAR, TURBULENT AND TRANSITIONAL FLOW
What is flow? How is flow described using the Reynold’s Number? What is its practical use in the real
world?
The objective of the experiment is to determine the Reynold’s Number in pipe flow and classify
whether the flow is laminar, turbulent or transitional.
What you need: Reynold’s number apparatus, ink, graduated cylinder, stopwatch
What to do:
1.
Note the inside diameter of the pipe.
2.
Measure the water temperature and determine the its kinematic viscosity from the table
below.
Temperature Kinematic Viscosity, π Temperature Kinematic Viscosity, π
°C
(m2/s)
°C
(m2/s)
15
1.138 X 10 -6
20
1.002 X 10 -6
-6
16
1.108 X 10
21
9.780 X 10 -7
-6
17
1.080 X 10
22
9.550 X 10 -7
18
1.053 X 10 -6
23
9.330 X 10 -7
19
1.027 X 10 -6
24
9.110 X 10 -7
3.
Fill the overhead tank with water. Once filled, turn
on the valve to produce a low but constant rate of
flow. The flow visualization pipe must be flowing full.
4.
With the dye control valve closed, fill in the dye
reservoir.
5.
Open the dye injector to allow it to flow in the pipe.
Adjust the discharge valve until slow flow is
achieved.
6.
When flow is constant, use a graduated cylinder to
collect water at the discharge pipe while taking
the time elapsed. The volumetric rate is then
computed as:
π=
ππππ’ππ
πΈππππ ππ ππππ
7.
Do at least 3 trials for this. Observe and note the dye patterns during this flow.
8.
Record the volume and time in the table.
9.
Compute the Reynold’s Number using the formula:
π =
π·π
π
Where:
π = Reynold’s Number
π· = pipe diameter
π = velocity = discharge divided by the cross-sectional area of the pipe =
π = kinematic viscosity of water
Indicate whether the flow is Laminar (π ≤ 2000), Turbulent (π ≥ 3000)
10.
Repeat this procedure for a faster flow and then for transitional flow.
11.
For transitional flow, slowly turn the pipe flow valve to establish laminar flow. The injected
dye will flow downstream in a threadlike pattern for very low flow rates.
12.
Once steady-state is achieved, open the valve slightly to increase the water flow rate.
Observe what happens to the dye. Its pattern may change yet the flow may still appear
to be laminar. This is the beginning of transition.
13.
Continue increasing the flow until flow becomes turbulent. This is the end of transition.
14.
Compute the Reynold’s Number. For transitional flow, 2000 < π <3000.
Show that Reynold’s Number is a dimensionless parameter. Describe the dye/ ink patterns created
by each type of flow. Would you be able to identify when and where these types of flow occur?
What significant value does this have in the civil engineering practice? These questions should be
answered in the Discussion of theory.
Research on how to compute for Reynold’s number when the fluid flow is not in a pipe. Give at
least two examples of this.
Prepare the Data and Results in the format shown below.
Data and Results:
Pipe Diameter:
Water temperature:
Trial
1
2
3
4
5
6
7
8
9
Volume,
cm3
1.286 cm
_____ °C (Refer to table in step 2 for π)
Time,
s
Discharge,
m3/s
Velocity, V
m/s
Reynold’s Number
π·π
π =
π
Type of Flow
LAMINAR
LAMINAR
LAMINAR
TRANSITIONAL
TRANSITIONAL
TRANSITIONAL
TURBULENT
TURBULENT
TURBULENT
The complete data and results table shall be shall be reflected on both the individual and group
reports. All computational problems shall be included in the problem set at the end of the individual
report. Please refer to Assignment Guide for the format and rubrics for assessment.
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