CIVL 3120 Lab Exp 03_Drag and Hydraulic Jump
pdf
keyboard_arrow_up
School
Toronto Metropolitan University *
*We aren’t endorsed by this school
Course
20
Subject
Aerospace Engineering
Date
Jan 9, 2024
Type
Pages
9
Uploaded by GrandDovePerson42
CIVL 3120: Hydraulics
Laboratory experiment 3
Part 1: Drag measurements
Part 2: Energy dissipation in a hydraulic jump
CIVL 3120: Laboratory experiment 3
Drag measurement & Energy dissipation in a hydraulic jump
2
Table of contents
1.
Introduction
.............................................................................................................................
3
1.1
Learning objectives & outcomes
......................................................................................
3
1.2
Background and theory
....................................................................................................
3
2.
Methods
...................................................................................................................................
4
2.1
Apparatus
.........................................................................................................................
4
2.1.1
Technical data
...........................................................................................................
5
2.1.2
Lab safety
..................................................................................................................
5
2.2
Procedure
..........................................................................................................................
5
2.2.1
Data collection
..........................................................................................................
6
3.
Analysis
...................................................................................................................................
8
3.1
Discussion questions
........................................................................................................
8
4.
Lab report requirements
...........................................................................................................
9
5.
References
...............................................................................................................................
9
CIVL 3120: Laboratory experiment 3
Drag measurement & Energy dissipation in a hydraulic jump
3
1.
Introduction
1.1
Learning objectives & outcomes
Part 1:
•
Identify standard terminology used in connection with drag and lift forces in fluids.
•
Understand the relationship between angle of attach and drag force for aerofoil.
Part 2:
•
study the flow pattern and length of a jump
•
determine the relationships between sequent depth, initial depth, Froude number, energy
loss, and the location and lengths of the hydraulic jump
•
compare the measured and theoretical flow depth values to form a hydraulic jump
1.2
Background and theory
Part 1:
External flow around objects submerged in fluids result in two forces: drag (due to pressure or
friction) and lift. Drag acts in the direction of fluid flow, whereas lift acts perpendicular the
motion of the fluid. The drag force on a submerged object is given by the following equation:
where
F
D
is the drag force,
C
d
is the drag coefficient,
ρ
is the density of the fluid,
U
0
is the
approach velocity, and
A
is the frontal area of the object. The drag coefficient is a function of
several factors, including the shape of the body, the Reynold’s number, and surface roughness.
The drag on an object is due to a combination of skin friction drag and pressure drag.
Streamlining is the process of reducing drag by minimising both skin friction and pressure drags.
Part 2:
This laboratory experiment is designed to demonstrate a hydraulic jump using weirs. Hydraulic
jumps occur naturally and they can also be made to occur where energy dissipation is required.
Weirs are controlled structures or barriers that can be used in an open channel to accomplish
many roles, including used to raise the water level, or for energy dissipation to prevent erosion
caused by low flow rates.
The flow regime in an open channel flow is determined using the Froude number. When the
Froude number is below 1 the flow is labelled subcritical, whereas when flow is above 1 is
labelled supercritical. A hydraulic jump is a flow phenomenon in which the flow regime changes
from supercritical flow upstream of the jump to subcritical flow downstream of the jump.
The specific type of weir that will be used for this experiment is called a “Ogee-crested weir”
with a steep outlet. Ogee-crested weirs are fixed and is designed to replicate a dam.
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
CIVL 3120: Laboratory experiment 3
Drag measurement & Energy dissipation in a hydraulic jump
4
2.
Methods
2.1
Apparatus
Part 1:
The TecQuipment AF10 air flow bench and AF12 Drag force apparatus (Figure 2) will be used
to determine the drag coefficient of an aerofoil for different angle of attacks.
Figure 1: The AF12 Drag force apparatus to be used in conjunction with the AF10 air flow bench
(Markland, 2015)
Part 2:
The Experimental flume with an Ogee-crested weir with a steep outlet will be used for this
experiment as shown in the figure below.
Figure 2: Profile view of a hydraulic jump in the experimental flume (Linke, 2015)
CIVL 3120: Laboratory experiment 3
Drag measurement & Energy dissipation in a hydraulic jump
5
2.1.1
Technical data
The measurement section of the flume is 309 mm wide, 450 mm deep, and 5000 mm long. The
dimensions of the Ogee-crested weir with a steep outlet are shown in the figure below.
Figure 3: Dimensions of the ogee-crested weir used in this experiment (Linke, 2015)
2.1.2
Lab safety
All in-person lab participants must wear lab coats and safety goggles and follow all the lab safety
procedures.
2.2
Procedures
Part1:
1.
Raise the manometer tank on the airflow bench to its maximum height.
2.
Ensure that the aerofoil is securely attached and set at 0
o
.
3.
Adjust the weight to ensure equilibrium and record the tare weight.
4.
Turn the fan on and its highest velocity, and adjust the weight to achieve equilibrium.
5.
Record the weight and the pressures from the pitot-static system.
6.
Repeat at different velocities, recording 4 or 5 values.
7.
Repeat the entire process while adjusting the angle of attack to 10 and 20
o
.
Part 2:
1.
Ensure that the slope of the Experimental Flume is set to 0%.
2.
Install the Ogee-Crested weir with a steep outlet inside the flume in a horizontal position.
This step may already be done for you. Ensure that there are no loose objects or tools
inside the flume, as this can damage the water pump.
3.
Turn on the Experimental Flume and set the flow rate to 80 m
3
/h.
4.
Then, using a ruler, measure the upstream water level (h
0
).
5.
Measure the supercritical water level between the weir and the hydraulic jump (h
1
).
6.
Measure the downstream water level (h
2
).
7.
Measure the length of the hydraulic jump (L).
8.
After you have taken your four measurements, decrease the flow rate in increments of 20
m
3
/h.
9.
Repeat steps 4 – 7 until you reach the last flow rate of 20 m
3
/h.
10.
Turn the water pump off.
CIVL 3120: Laboratory experiment 3
Drag measurement & Energy dissipation in a hydraulic jump
6
2.2.1
Data collection
Part 1:
Angle of attack = 0
o
Angle of attack = 10
o
Angle of attack = 20
o
Tare weight =
Tare weight =
Tare weight =
P1
(mm H
2
O)
P2
(mm H
2
O)
F (g)
P1
(mm H
2
O)
P2
(mm H
2
O)
F (g)
P1
(mm H
2
O)
P2
(mm H
2
O)
F (g)
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
CIVL 3120: Laboratory experiment 3
Drag measurement & Energy dissipation in a hydraulic jump
7
Part 2:
Q (m
3
/h)
Length of the
jump, L (mm)
Upstream water
level, h
0
(mm)
Water level
before jump, h
1
(mm)
Downstream water
level after jump, h
2
(mm)
CIVL 3120: Laboratory experiment 3
Drag measurement & Energy dissipation in a hydraulic jump
8
3.
Analysis
Part 1: Drag force measurement
1.
Calculate the drag force using the net weight at each velocity and at each angle of attack;
present your results in tabular form.
2.
Use the above data to calculate the drag coefficient using the planform area (i.e. the chord
and span of the aerofoil); present your results in tabular form.
3.
Determine the velocity and Reynold’s number for each data point; present your results in
tabular form.
4.
Plot the net drag force vs pressure difference for the aerofoil at each angle of attack on
the same chart and comment on the results.
5.
Plot the drag coefficient vs Reynolds number for the aerofoil at each angle of attack on
the same chart and comment on the results.
6.
Plot the net drag force vs drag coefficient for the aerofoil at each angle of attack on the
same chart and comment on the results.
Part 2: Energy dissipation in a hydraulic jump
1.
Derive an expression to calculate h
1
as a function of h
2.
2.
Plot the ratio of (h
2
/h
1
) against the Froude number at h
1
for the observed and calculated
(using the expression from step 1) h
1
; discuss any discrepancies between the curves.
3.
Plot the ratio of head loss and the initial depth (
Δ
h/h
1
) vs. the Froude number at h
1
for the
observed and calculated h
1
(using the expression from step 1); discuss any discrepancies
between the curves.
4.
Plot the ratio of hydraulic jump length and the depth (L/h
2
) vs. Froude number Fr
1
. What
does it show you?
5.
Calculate the specific energy, E, at h
0
, h
1
, h
2
, and the change in energy between h
1
and h
2
;
comment on the difference.
3.1
Discussion questions
1.
What is the impact, if any, of the Reynold’s number on the drag coefficients? What
impact does the Reynold’s number have on the formation of wake or boundary layer and
the pressure difference around these objects?
2.
Why do you think golf balls have a dimpled surface?
CIVL 3120: Laboratory experiment 3
Drag measurement & Energy dissipation in a hydraulic jump
9
3.
In your opinion, what is the engineering significance of a hydraulic jump? When is it
needed?
4.
Why do engineers purposely create a hydraulic jump just downstream of a spillway?
5.
Why it is essential for an engineer to know the exact downstream location of the
hydraulic jump?
6.
What impact does the flowrate have on the location of the hydraulic jump? Why does the
location change?
7.
What would happen if the flowrate was increased beyond 80 m
3
/h?
4.
Lab report requirements
Lab reports should be completed in groups.
Each report should include a title page, an abstract, table of content, a brief overview of
objectives, the data collected, numerical results and discussion questions. Please cite any
references used.
5.
References
Linke U. (2015). HM 162.32 Ogee-Crested Weir with 2 Weir Outlets. Version 1.3.
G.U.N.T.
Gerätebau, Barsbüttel, Germany.
Markland, E. (2015). A first course in airflow. TecQuipment Ltd, Nottingham, United Kingdom
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help