Reynolds Experiment - Slide/Image Title Audio/Text
Introduction and
Objectives
Music starts
1
Text: This video will explain how to use the apparatus for Reynold’s experiment as well as some of the theory behind the experiment.
Music ends
2
Osborne Reynolds Osborne Reynolds, a British engineer was the first to observe and classify the different flow regimes for pipe flow.
3
His experiment involved running water through a transparent pipe at various flow rates injecting a small amount of dye at each flow rate and observing the resulting flow patterns.
4
Type of Flows For relatively small flow rates the dye streak will remain a well defined line as it flows along; this is known as Laminar Flow.
5
Page 1 of 7

6
7
8
9
10
Visual Observations
Reynolds Numbers
For an intermediate flow rate the dye streak fluctuates through time and space and intermittent bursts of irregular behaviour appear along the stream; this is known as transitional flow
For relatively large flow rates the dye streak almost immediately becomes blurred and spreads across the entire pipe in a random fashion.
This is known as turbulent flow.
To quantify his visual observations, Reynolds developed a dimensionilist parameter known as Reynolds’ number. Reynolds’ number physically represents the ratio of inertial forces to viscous forces and is defined as shown where
V is the average velocity, d is the characteristic length represented by the pipe diameter p “row” is the density of the fluid, u“mew is the … viscosity of the fluid, and v “new” is the kinematic viscosity of the fluid.
A low Reynolds number is considered to be laminar flow, a high
Reynolds number is turbulent flow and a number in between is transitional flow.
In general, for pipe flow a Reynolds number of less than 2100 indicate laminar flow, and a number greater than 4000 indicates turbulent flow.
Page 2 of 7

13
14
11
12
15
Setup the equipment
16
17
18
19
Before setting up the experiment, make sure you have all the required equipment:
The main apparatus, the constant head reservoir, red dye, a ruler, a graduated cylinder, a stop watch and a thermometer.
To setup the apparatus:
1.
place the white board on a bench and adjust the level using the small screw in the front
2.
Place the bucket on the same bench.
3.
Take the red tube labeled “inflow from tap” and put the free end over the tap.
4.
Take the inflow tube from the apparatus and attach it to the nozzle labeled “outflow to apparatus” on the bucket
5.
Place the overflow tube from the bucket into sink, place the outflow tube from the apparatus into the sink as well
6.
to fill the syringe with dye, take the plunger out , put the needle together and fill it with red dye.
7.
empty the needle into the syringe and repeat this if necessary place the plunger back onto the syringe without pressing down so that none of the dye runs out
Page 3 of 7

20
21
22
23
24
Before allowing water to enter the system, make sure the outflow valve is closed
Turn the tap on to fill the bucket and tubing with water.
When the tubing is full, open the valve to flush the system of any air bubbles then close it again.
Collect Data and
Measurements
A constant head is established when water starts exiting the overflow tube. A this point the apparatus is fully setup and your almost ready to begin the experiment. Leave the tap running
Before starting the experiment you should collect data and measurements that you will need later on for your analysis. Determine the temperature and head loss of the system.
Page 4 of 7

27
28
25
26
29
30
To calculate the head loss, measure the elevation of the water on both piezometers and subtract to get the difference.
Measure the length between the two piezometers. Divide the head loss by this length to determine the head loss per unit length.
Start Experiment
Measure and record the diameter of the tube for future reference
To start the experiment, turn the outflow valve to the first black mark.
This should create a small stream of water flowing through the system.
Slowly push down on the syringe to inject dye into the system.
Sketch the observed behaviour.
Page 5 of 7

33
34
31
32
35
36
Once that is complete, determine the head loss in the system again by measuring the elevation of water in the piezometers next determine the flow rate through the system
Measurement of Flow
Rate
The flow rate is measured using a graduated cylinder and a watch.
Place the outflow tube into the graduated cylinder keeping the tube at a constant elevation
After one minute take the outflow tube out. Measure and record the volume of water obtained in the specific time.
For turbulent flow the water may be moving too fast so the time period may need to be reduced to 30 seconds
Measure the flow rate three times to get an accurate reading.
Page 6 of 7

39
40
37
38
Once the sketch, head loss and flow rate for this setting have been determined, turn the outflow valve to the next black mark.
Do this for all five marks on the outflow valve. Repeat the entire experiment again to ensure that you have the correct data.
Closing Instructions Discussion questions are outlined in your lab handout. If you have any questions please see your TA’s.
Closing Credits Closing Credits
Page 7 of 7