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CC 303 hydraulics 1
APPRECIATION
Thanks God, we give thanks to the Almighty for His grace and we can set up a report entitled
‘highway laboratary (CC 302)'. Appreciation and gratitude goes to Pn. Hazilah as lecturer
highway engineering for their help, cooperation, guidance, advice and practical ideas that poured
along the run.
Thankfully we have colleagues who help others and help each other work, here are our group
members, Hilmi, Syahiruddin, Zaim, Luqman, Nurul Shafiqa, Noor Syafiqah, Asyikin, and
Amiera are always striving to complete this highway laboratary work.
Moreover, not least thank you to friends, colleagues and all those who have helped us either
directly or indirectly. Hopefully reports this produced a certain extent helped to increase the
effectiveness student learning and enhance students' knowledge in the subjects studied civil
engineering in general and in particular Highway Engineering.
Thank you.
REYNOLDS NUMBER 1
CC 303 hydraulics 1
INTRODUCTION
The purpose of this experiment is to illustrate the influence of Reynolds number on pipe flows.
Reynolds number is a very useful dimensionless quantity (the ratio of dynamic forces to viscous
forces) that aids in classifying certain flows. For incompressible flow in a pipe Reynolds number
based on the pipe diameter, ReD = VaveDρ/μ, serves well. Generally, laminar flows correspond
to ReD < 2100, transitional flows occur in the range 2100 < ReD < 4000, and turbulent flows
exist for ReD > 4000. However, disturbances in the flow from various sources may cause the
flow to deviate from this pattern. This experiment will illustrate laminar, transitional, and
turbulent flows in a pipe.
The apparatus used here to demonstrate ‘critical velocity’ is based on that used by Professor
Reynolds who demonstrated the nature of the two modes of motion flowing in a tube, example
laminar and turbulent. The unit is designed to be mounted on P6100 hydraulic Bench and the
quantity of water flowing through it can be measured and timed using the Hydraulic Bench
Volumetric Tank and a suitable stopwatch. A bell mounted glass tube 790mm long overall by
16mm bore is mounted horizontally and concentrically in a much larger diameter tube fitted with
baffles. A uniform supply of water can then be made to flow along the 16mm bore tube.
The unit is fitted with a constant head tank and the flow rate which can be varied by adjustment
to the head tank height, can be measured using the volumetric tank.
A dye injector is situated at the entrance to the 16 mm bore tube and thus it is possible to detect
whether the flow is streamline or turbulent.
REYNOLDS NUMBER 2
CC 303 hydraulics 1
Critical velocities and Reynolds number
Reynolds obtained the loss of pressure head in a pipe at different flow rates by measuring the
loss head (hf) over a known length of pipe (l), from this slope of the hydraulic gradient (i) was
obtained.
i=hfl
When Reynolds plotted the results of his investigation of how energy head loss varied with the
velocity of flow, he obtained two distinct regions separated by a transition zone. In the laminar
region the energy loss per unit length of pipe is directly proportional to the mean velocity. In the
turbulent flow region the energy loss per unit length of pipe is proportional to the mean velocity
raised to some power, ƞ. The value of ƞ being influenced by the roughness of the pipe wall.
hflα v1.7 For smooth pipes in this region but
hflα v2 for very rough pipes.
Examplehflα v1.7¿2.¿. The dimensionless unit Reynolds number (Re) = ρvd/μ and has a value
below 2000 for laminar flow and above 4000 for turbulent flow (when any consistent set of units
is used) – the transition zone lying in the region of Re 2000 – 4000 (example ‘lower critical
velocity’ LCV at Reynolds number of 2000 and ‘upper critical velocity’ UCV at a Reynolds
number of 4000)
Note that the value of Re obtained in experiments made with ‘increasing’ rates of flow will
depend on the degree of care which has been taken to eliminate disturbance in the supply and
along the pipe. On the other hand, experiment made with ‘decreasing’ flow rates will show a
value of Re which is very much less dependent on initial disturbance.
REYNOLDS NUMBER 3
CC 303 hydraulics 1
OBJECTIVE
The objective of the experiment are :
To observe the characteristics of the flow of a fluid in a pipe, this may be laminar, transitional or turbulent flow by measuring the Reynolds number and the behavior of the flow.
To calculate and identify Reynolds number (Re) for the laminar, transitional and turbulent flow.
To demonstrate the differences between laminar, turbulent, and transitional fluid flow, and the Reynolds’s numbers at which each occurs.
REYNOLDS NUMBER 4
CC 303 hydraulics 1
THEORY
Osborne Reynolds in 1883 conducted a number of experiments to determine the Laws of
Resistance in pipes to classify types of flow. Reynolds number 'Re' is the ratio of inertia force to
the viscous force where viscous force is shear stress multiplied area and inertia force is mass
multiplied acceleration. Reynolds determined that the transition from laminar to turbulent flow
occurs at a definite value of the dimensionally property, called Reynolds number :
Where:
v = flow velocity (m/s)
ρ = density (kg/m³)
d = inside diameter of pipe section (m)
μ = dynamic viscosity of the fluid (kg/ms)
Q = volumetric flow rate (m³/s)
A = cross sectional area of the pipe (m²)
ν = kinematics viscosity (m²/s)
REYNOLDS NUMBER 5
CC 303 hydraulics 1
Reynolds carried out experiments to decide limiting value of Reynold's number to a quantitatively decide whether the flow is laminar or turbulent. The limits are as given below:
Laminar when Re < 2300 Transition when 2300 < Re < 4000 Turbulent when Re > 4000
Figure 2 : Three flow regimes: (a) laminar, (b) transitional & (c) turbulent
The motion is laminar or turbulent according to the value of Re is less than or greater than a certain value. If experiments are made with decreasing rate of flow, the value of Re depends on degree of care which is taken to eliminate the disturbances in the supply or along the pipe. On the others hand, if experiments are made with decreasing flow, transition from turbulent to laminar flow takes place at a value of Re which is very much depends on initial disturbances. The valve of Re is about 2000 for flow through circular pipe and below this the flow is laminar
REYNOLDS NUMBER 6
CC 303 hydraulics 1
in nature. The velocity at which the flow in the pipe changes from one type of motion to the other is known as critical velocity.
APPARATUS
The following apparatus is required.
NO NAMES INSTRUMENT
1) Hydraulic bench
2) Osborne Reynolds Demonstration Apparatus
3) Stop watch
4) Dye
REYNOLDS NUMBER 7
CC 303 hydraulics 1
5) Thermometer
6) Measuring cylinder
REYNOLDS NUMBER 8
CC 303 hydraulics 1
Figure 1: Osborne Reynolds Demonstration Apparatus
1. Base Plate 8. Test Pipe Section
2. Water Reservoir 9. Ball Block
3. Overflow Section 10. Waste Water Discharge
4. Aluminium Well 11. Connections for Water Supply
5. Metering Tap 12. Drain Cock
6. Brass Inflow Tip 13. Control valve
REYNOLDS NUMBER 9
CC 303 hydraulics 1
7. Flow-Optimised Inflow
PROCEDURE
(After choosing a suitable sampling site, follow the procedures below)
1. Firstly, the apparatus is set up and measure and note down diameter of pipe and also
room temperature. Fill the aluminium well with dye, the metering tap (dye flow control
valve) and drain cock must be closed.
2. Switch on the pump, carefully open the control valve above the pump and adjust the tap
to produce a constant water level in the reservoir. After a time the test pipe section is
completely filled.
3. Open the drain cock slightly to produce a low rate of flow into the test pipe section.
4. Open the metering tap and the dye is allowed to flow from the nozzle at the
entrance of the channel until a coloured stream is visible along the test pipe section. The
velocity of water flow should be increased if the dye accumulates around the nozzle.
5. Adjust the water flow until a laminar flow pattern which is a straight thin line or
streamline of dye is able to be seen along the whole test pipe section.
6. Collect the time in seconds for the 10 liters volume of coloured waste water that flows
down at the outlet pipe. The volume flow rate is calculated from the volume and a known
time.
7. Repeat step 5-6 with increasing rate of flow by opening the drain cock and the flow
pattern of the fluid is observed as the flow changes from laminar to transition and
turbulent. Take five to six readings till the dye stream in the test pipe section breaks up
and gets diffused in water.
8. Clean all the apparatus after the experiment is done.
REYNOLDS NUMBER 10
CC 303 hydraulics 1
RESULT
END RESULTS
Inside diameter of pipe section,d = 0.010 m
Cross sectional area of the pipe, A = 7.854x10−3 m²
Density of water, ρ = 1000 kg/m3
Kinematics viscosity of water at room temperature, ν = 0.697 m²/s (see Table 1)
Average room temperature,Ө = 37 ºC
Run No.
Volume, V ( m3)
Time, t (S)
Flow rate, Q(m3/s)
Velocity, v (m/s)
Reynolds Number(RE)
Type of Flow
1 0.01 2.55 4 x 10−3 0.51 7.32 x 10−3 Laminar
2 0.01 2.85 3.51 x 10−3 0.45 6.46 x 10−3 Laminar
3 0.01 3.25 3.125 x 10−3 0.40 5.73 x 10−3 Laminar
4 0.01 3.35 3.030 x 10−3 0.39 5.60 x 10−3 Laminar
5 0.01 3.75 2.703 x 10−3 0.34 4.88 x 10−3 Laminar
6 0.01 3.95 2.564 x 10−3 0.33 4.73 x 10−3 Laminar
Formula :
REYNOLDS NUMBER 11
CC 303 hydraulics 1
CALCULATION
Bell mounted glass tube (length =790 mm, diameter=16mm)
Therefore the area,A = πd²/4 = 2.01×10-4 m²
Reynolds number (dimensionless constant)
Q = ѵs
(m³/s)
Q = volumetric flowrateѴ= volume s= time
V = QA
V=VelocityA=Area of the pipe
Re = ρvdμ
Where,
ρ = density (kg/m³ )
d = diameter (m)
V = velocity (m/s)
µ = viscosity (kg/ms)
Water density,ρ = 1000 kg/m³
Water viscosity, µ = 1.0× 10ˉ³kg/ms
REYNOLDS NUMBER 12
CC 303 hydraulics 1
No. Flow Rate & Velocity Re = v dν
Description
1
V = 0.01m³
Q = 0.01m ³2.55 s
= 4 x 10−3 m³/s
v = 4 x10−3m ³ /s
7.854 x10−3m2
= 0.51 m/s
Re = (0.51)(0.010)
0.697
= 7.32 x 10−3
Laminar
2
V = 0.01m³
Q = 0.01m ³2.85 s
= 3.51 x 10−3 m³/s
v = 3.51x 10−3m ³/s7.854 x10−3m2
= 0.45 m/s
Re = (0.45)(0.010)
0.697
= 6.46 x 10−3
Laminar
3
V = 0.01m³
Q = 0.01m ³3.25 s
= 3.125 x 10−3m³/s
v = 3.125x 10−3m ³/ s
7.854 x10−3m2
= 0.40 m/s
Re = (0.40)(0.010)
0.697
=5.73 x 10−3
Laminar
V = 0.01m³
REYNOLDS NUMBER 13
CC 303 hydraulics 1
4
Q = 0.01m ³3.35 s
= 3.030 x 10−3m³/s
v = 3.030x 10−3m ³/ s
7.854 x10−3m2
= 0.39 m/s
Re = (0.39)(0.010)
0.697
= 5.60 x 10−3
Laminar
5
V = 0.01m³
Q = 0.01m ³3.75 s
= 2.703 x 10−3 m³/s
v = 2.703x 10−3m ³/ s
7.854 x10−3m2
= 0.34 m/s
Re = (0.34 )(0.010)
0.697
= 4.88 x 10−3
Laminar
6
V = 0.01m³
Q = 0.01m ³3.95 s
= 2.564 x 10−3 m³/s
v = 2.564 x10−3m ³ /s
7.854 x 10−3m2
= 0.33 m/s
Re = (0.33)(0.010)
0.697
= 4.73 x 10−3
Laminar
REYNOLDS NUMBER 14
CC 303 hydraulics 1
REYNOLDS NUMBER 15
CC 303 hydraulics 1
DISCUSSION
Laminar flow- highly ordered fluid motion with smooth streamlines.
Transition flow -a flow that contains both laminar and turbulent regions.
Turbulent flow -a highly disordered fluid motion characterized by velocity and
fluctuations and eddies.
According to the Reynolds`s experiment, laminar flow will occur when a thin filament of dye
injected into laminar flow appears as a single line. There is no dispersion of dye throughout the
flow, except the slow dispersion due to molecular motion. While for turbulent flow, if a dye
filament injected into a turbulent flow, it disperse quickly throughout the flow field, the lines of
dye breaks into myriad entangled threads of dye.
In this experiment we have to firstly is to observe the characteristic of the flow of the fluid in
the pipe, which may be laminar or turbulent flow by measuring the Reynolds number and the
behaviour of the flow, secondly to calculate the range for the laminar and turbulent flow and
lastly to prove the Reynolds number is dimensionless by using the Reynolds number formula.
After complete preparing and setup the equipment we run this experiment. But firstly we
have to calculate the area of bell mounted glass tube, the viscosity of water and the density of
water. The density of water is 1000 kg/m³, the area of glass tube is 2.01×10-4 m², while the
viscosity of water is 1.0× 10ˉ³kg/ms, this is done for easy step by step calculation.
We observe that the red dye line change with the increasing of water flow rate. The shape
change from thin threads to slightly swirling which still contains smooth thin threads and then
fully swirling. We can say that this change is from laminar flow to transitional flow and then to
turbulent flow and it’s not occurs suddenly.
REYNOLDS NUMBER 16
CC 303 hydraulics 1
CONCLUSION
Finally, As the water flow rate increase, the Reynolds number calculated also increase
and the red dye line change from thin thread to swirling in shape.
Laminar flow occurs when the Reynolds number calculated is below than 2300;
transitional flow occurs when Reynolds number calculated is between 2300 and 4000 while
turbulent flow occurs when Reynolds number calculated is above 4000. It is proved that the
Reynolds equation is dimensionless, no units left after the calculation
REYNOLDS NUMBER 17
CC 303 hydraulics 1
RECOMMENDATION
Compare with the result diagram in the laboratory, there are bit different between the
results collected. This might be some of parallax error such as the slow response during
collecting the water, the position of eyes during taking the value of water volume, time taken for the
volume of water and regulating the valve which control the flow rate of water unstably.
During the experiment there are several precaution steps that need to be alert. The
experiment should be done at suitable and unshaken place. To get appropriate laminar smooth
stream flow, the clip and the valve which control the injection of red dye must be regulate slow
and carefully. When removing the beaker from the exit valve, we notice that some water still
enter the beaker because of the slow response between the person who guide the stop watch and
collecting beaker. So to avoid this parallax error, it is better to take same person who guard the stop watch
and the collecting beaker.
Lastly, do this experiment at steady place, control the clip and valve carefully to get long thin of
laminar dye flow, and remove the beaker which uses to collect the amount of water at sharp when the
time is up, to avoid error flow rate error.
REYNOLDS NUMBER 18
CC 303 hydraulics 1
REFERENCES
Internet References
http://en.wikipedia.org/wiki/ReynoldsNumber
Book References
Modul C 3009 ( Hidraulik 1 Jabatan Kejuruteraan Awam Politeknik Kota Kinabalu )
High-Reynolds number Rayleigh-Taylor turbulence Authors: D. Livescu; J. R. Ristorcelli; R. A. Gore; S. H. Deana; W. H. CabotDOI: 10.1080/14685240902870448Published in: Journal of Turbulence, Volume 10, N 13 2009First Published on: 01 January 2009
Structure of a high-Reynolds-number turbulent wake in supersonic flowJ. P. Bonnet, V. Jayaraman and T. Alziary De Roquefort Laboratoire d'Etudes Aérodynamiques et Thermiques, Laboratoire Associé au C.N.R.S. 191, Centre d'Etudes Aérodynamiques et Thermiques, 43 Route de l'Aérodrome, 86000 Poitiers, France.Journal of Fluid Mechanics (1984), 143:277-304 Cambridge University PressCopyright © 1984 Cambridge University Pressdoi:10.1017/S002211208400135X
Lecturer References
( Pn Hazilah Binti Mohamad, Lecturer of Hydraulics 1 DKA3B )
REYNOLDS NUMBER 19