FM Practical Experiment and Report

BET 208 Fluid Mechanics
Practical Experiment and Report

You need to conduct practical experiments as well as to analyse and interpret data and draw
conclusion to explore properties of a number of fluids and to verify laws and principles of
fluid mechanics. Written reports detailing the full process of each experiment are required for
assessment. Each experiment report will be marked out of 10. All the experiment reports will
contribute to 15% of the final assessment.
Provide details of the following experiments

1. Measuring viscosity of a fluid by a visocitymeter or Stroke’s law.
2. Measuring specific gravity of a liquid by a hydrometer.
3. Measuring hydraulic grade line (HGL) and energy grade line (EGL) and verification
of Bernoulli’s equation.
Marking distribution for each Practical Experiment Report

Element Description Marks
Title Page Title of experiment, subject, lecturer, date, your name & 0.5
student ID, Group number.
Table of Contents Word will generate this automatically for you if you use 0.5
Heading styles (for the whole document).
Introduction A brief description of the experiment you have 1
performed.
Definitions Definitions of the key terms of the the experiment (you 1

can follow the definitions provided in the standard)
Required Equipment List the apparatus required for performing the experiment 1
and briefly discuss their functions.
Test Procedure Explain the procedure of the test in a concise manner (1 1

page max.).
Data sheet Summary of data collected during experiment (preferably 2

using data sheet or appropriate table).
Analysis and Perform required analysis of the collected data and 2
Interpretation interpret the results.
Conclusion Conclusions and limitations of your experiment. 1
Page 1 of 5
Measuring the viscosity of a liquid using Strokes’ Law
The force of viscosity on a small sphere moving through a viscous fluid is given by:
where Fd is the frictional force – known as Stokes' drag – acting on the interface between the
fluid and the particle (in N),μ is the dynamic viscosity (kg /m*s),R is the radius of the
spherical object (in m), and v is the particle's velocity (in m/s).
At terminal (or settling) velocity, the excess force Fg due to the difference of the weight of the
sphere and the buoyancy on the sphere, (both caused by gravity)
with ρp and ρf the mass density of the sphere and the fluid, respectively, and g the
gravitational acceleration. Demanding force balance: Fd = Fg and solving for the velocity V
gives the terminal velocity Vs. Note that since buoyant force increases as R3 and Stokes drag
increases as R, the terminal velocity increases as R2 and thus varies greatly with particle size
as shown below. If the particle is falling in the viscous fluid under its own weight due to
gravity, then a terminal velocity, or settling velocity, is reached when this frictional force
combined with the buoyant force exactly balances the gravitational force. The resulting
terminal velocity (or settling velocity) is given by
where vs is the particle's settling velocity (m/s) (vertically downwards if ρp > ρf, upwards if
ρp < ρf ), g is the gravitational acceleration (m/s2), ρp is the mass density of the particles
(kg/m3), ρf is the mass density of the fluid (kg/m3) and μ is the dynamic viscosity (kg /m*s).
https://www.youtube.com/watch?v=Q7VZh0dI35M
https://www.youtube.com/watch?v=977wNbFiYlc
Page 2 of 5
Using A Hydrometer
http://www.lumcon.edu/education/K-12/studentdatabase/hydrometer.asp
https://www.youtube.com/watch?v=lRWD8Bcemuw
A hydrometer is a tool scientists use to measure
the specific gravity of liquids. Specific gravity is the
ratio of the mass of a liquid to the mass of an equal
volume of pure water. Because the density of a liquid
changes with temperature, hydrometers are calibrated
for different reference and sample temperatures.
Classically, specific gravity was measured using the
density of water at 4ºC (the temperature of maximum
density for pure water). Today, most hydrometers used
in water quality testing are calibrated for with a
reference temperature of 60ºF. These hydrometers will
be inscribed with "60ºF/60ºF" on their necks denoting
that the reference density was measured at 60ºF and
the sample should be at 60ºF. Because specific gravity
measures the mass of a liquid over the mass of
distilled water, specific gravity is unitless.
Hydrometers come with different scales depending on
the characteristics of the liquid the user is measuring.
The hydrometers used for the Bayouside Classroom
program range from 0.940 to 1.010 and are calibrated
at 60ºF/60ºF. The measurement made with the
hydrometer can be used to calculate the salinity of a
water sample.
Using a hydrometer is quite simple. The user must be

careful, though, to not break the the hydrometer or the
cylinder as they are made from glass. Follow the easy
to follow directions below.
1. Fill the glass cylinder with sample water.

2. Put the hydrometer with the bulb end down. It will bob up and down in the
sample. Note that the sample may overflow from the cylinder.
3. Assure that the hydrometer is not in contact with the sides of the cylinder
and take the reading.
Page 3 of 5
Reading The Hydrometer
Extreme care should be taken when reading the
hydrometer; it is very easy to misinterpret the
scale. Once the hydrometer has stopped
bouncing up and down and the hydrometer is
not touching the walls of the cylinder, a
reading can be made. Note that a meniscus
forms on the neck of the hydrometer. Just as
reading the meniscus in a graduated cylinder,
the user must take the reading where the plane
of water is and not where the water clings up
the neck of the hydrometer. See the image to
the right. The correct reading of this
hydrometer is about 0.982.
Once the reading has been made, clean the cylinder and hydrometer. Carefully
place them into their protective packaging so they will not be broken.
Figure - Measuring Specific Gravity by a Hydrometer
Page 4 of 5
Figure - The static, dynamic, and stagnation pressures.
Figure - The hydraulic grade line (HGL) and the energy grade line (EGL) for free
discharge from a reservoir through a horizontal pipe with a diffuser.
https://www.youtube.com/watch?v=-oecDDrYfyY
Page 5 of 5

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BET 208 Fluid Mechanics

Practical Experiment and Report

Provide details of the following experiments

Marking distribution for each Practical Experiment Report

Definitions Definitions of the key terms of the the experiment (you 1

Test Procedure Explain the procedure of the test in a concise manner (1 1

Data sheet Summary of data collected during experiment (preferably 2

Conclusion Conclusions and limitations of your experiment. 1

Using a hydrometer is quite simple. The user must be

1. Fill the glass cylinder with sample water.

Figure - Measuring Specific Gravity by a Hydrometer

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