4.
EXPERIMENTS
4.1 Cussons P6231 Bernoulli's Apparatus allows two experiments to be
conducted
Experiment 1 Verification of Bernoulli's Equation
Experiment 2 Demonstration of Laminar and Turbulent Flow
4.2 Equipment Preparation
Position the Inlet Head Tank and the Variable Head Outlet Tank on the mounting studs
provided on the Hydraulic Bench working surface and connect the Bernoulli Apparatus
between them using the union connections. Connect the Bench Feed hose to the Inlet Head
Tank and attach an overflow hose to the overflow outlet of the Inlet Head Tank. Attach the
Dye Reservoir to the top of the Inlet Head Tank using the attached mounting clip and ensure
that the spring clip is attached to the rubber hose so that ink cannot flow to the injector
needle. Fill the ink reservoir with a water miscible dye, washable blue ink is recommended.
Make sure that the dye is free to flow through the dye injector needle when the spring clip is
adjusted. If a blockage of the ink does occur in the injector needle, this is usually caused by
a failure to wash out all the ink when the equipment has been previously used. The
blockage can normally be rectified by flushing the dye injection system thoroughly with clean
water. Remove the brass blanking plug from the side of the Inlet Head Tank and insert the
Dye Injector Needle so that the tip protrudes approximately 20mm into the transparent
Bernoulli Test section. In order to record the height of the water level in each of the
manometer tubes, a sheet of paper should be positioned as in figure 1.
EXPERIMENT 1 - VERIFICATION OF BERNOULLI'S EQUATION
Aim. To verify Bernoulli's equation by demonstrating the relationship between pressure
head and kinetic head.
Equipment Preparation. Prepare the equipment to the following specification
Inlet P6103 Constant Head Inlet Tank with overflow extension fitted.
Test Section P6231 Bernoulli's Apparatus
Exit P6104 Variable Head Outlet Tank
Manometer Insert a sheet of graph paper 440mm high by 325mm wide behind the manometer
tubes to provide an easy method of obtaining a record of the results.
Experimental Procedure.
1. Start the pump and initiate a flow of water through the test section. Regulate the
flow to the inlet head tank so that there is a small but steady overflow from the
reservoir. Adjust the swivel tube of the outlet tank to obtain a differential head.
2. Measure the height of the water level in each manometer tube by marking the paper
positioned behind the tubes and record on the test sheet. Measure the time taken to
fill the bench measuring tank from zero to 10 litres and record.
3. Increase the differential head between the inlet and outlet head tanks by 50mm
increments, until the water level in the centre manometer tubes drops off the scale.
For each condition record the heights of liquid in the manometer tubes by once
again marking the paper positioned behind the tubes and measure the flow rate.
Results and Analysis.
1. Record the results on a copy of the result sheet provided.
2. Calculate the flow rate for each set of results.
3. For each set of results calculate at the cross-section adjacent to each manometer
tube, the flow velocity and the Reynolds number.
4. Plot a graph of head against distance and also H + V2 / 2g against distance.
EXPERIMENT 2 - DEMONSTRATION OF LAMINAR AND TURBULENT FLOW
Aim. To demonstrate visually laminar (or streamlined) flow and its transition to turbulent flow
at a particular velocity.
Equipment Preparation. Prepare the equipment to the following specification
Inlet P6103 Constant Head Inlet Tank with overflow extension fitted.
Test Section P6231 Bernoulli's Apparatus
Exit P6104 Variable Head Outlet Tank
Manometer Insert a sheet of graph paper 440mm high by 325mm wide behind the manometer
tubes to provide an easy method of obtaining a record of the results.
Dye injection Fitted
Experimental Procedure.
1. Start the pump and initiate a flow of water through the test section. Regulate the
flow to the inlet head tank so that there is a small but steady overflow from P6103.
Adjust the swivel tube of the outlet tank to obtain a differential head of 20mm.
2. Raise the dye reservoir to the top of its column (the spring loaded bracket can be
freed by squeezing the two ends together between the fingers) and open the tube
clip.
3. Open the small cock on the base of the reservoir to permit dye to flow from the
nozzle at the entrance to the channel. This will be visible as a coloured stream
along the passage. If the dye accumulates around the nozzle, increase the velocity
of flow in the passage and/or check the flow from the dye reservoir.
4. Under laminar flow conditions the stream will be visible along the whole length of
the passage. If this is not so, reduce the flow until a continuous stream of dye is
visible along the passage.
5. Steadily increase the flow rate by increasing the total differential head, while
carefully observing the condition of the fluid in the channel. When instability occurs
leading to the break-up of the dye stream, note the position in the passage and
measure the corresponding value of the flow rate.
6. Continue to maintain close observation of the passage while further increasing the
flow rate until the whole system is turbulent with no visible dye stream at any point.
7. Reduce the flow rate to the point at which turbulence disappears and stable laminar
flow conditions are regained along the whole passage. Measure the flow rate and
position of the last traces of turbulence.
8. Continuous manipulation of the flow rate while observing the flow conditions may be
conducted as a useful visual aid to the appreciation of laminar and turbulent flow
conditions.
9. Switch off the pump and allow the apparatus to drain back to the main reservoir.
Note : Continuous use of the dye will tint the circulating water. When this becomes
severe the water should be changed. Do not use water containing dye in other
apparatus
10. Completely clean all the apparatus of any trace of water containing dye before
returning the apparatus to store.
Results and Analysis.
1. Record the results on a copy of the result sheet provided.
2. Calculate the flow rate for each set of results.
3. For each set of results calculate at the cross-section adjacent to each manometer
tube, the flow velocity and the Reynolds number.
4. For a set of results in which the flow changed from laminar to turbulent determine
the higher critical Reynolds number.
RESULTS SHEET P6231 BERNOULLI'S APPARATUS
EXPERIMENT 1 VERIFICATION OF BERNOULLI'S EQUATION
Results and Analysis
Water Temperature 3 Vicosity of Water
o Density of Water kg/m 2
C Ns/m
Quantity of Water Time to Collect Water Volumetric Flow Rate
Collected litres sec Q litres/min
1 2 3 4 5 6 7 8 9 10 11
Tapping Number
2 102.56 90.11 77.66 65.22 52.77 40.32 52.77 65.22 77.66 90.11 102.56
Flow Area mm
Static Head mm
Velocity m/s
Reynolds Number
Observations
RESULTS SHEET P6231 BERNOULLI'S APPARATUS
EXPERIMENT 1 VERIFICATION OF BERNOULLI'S EQUATION
Results and Analysis
Water Temperature 3 Vicosity of Water
o Density of Water kg/m 2
C Ns/m
Quantity of Water Time to Collect Water Volumetric Flow Rate
Collected litres sec Q litres/min
1 2 3 4 5 6 7 8 9 10 11
Tapping Number
2 102.56 90.11 77.66 65.22 52.77 40.32 52.77 65.22 77.66 90.11 102.56
Flow Area mm
Static Head mm
Velocity m/s
Reynolds Number
Observations
