| The Effect
of Different Shapes on Aerodynamic Drag |
Researched by Tyler S.
2003-04 |
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PURPOSE
The purpose of this experiment was to determine which vehicle shape
had the least amount of drag.
I became interested in this idea because I didn’t know that much about
aerodynamics and wanted to do something related to engineering.
The information gained from this experiment would help people who study
aerodynamics and engineers who design vehicles.
HYPOTHESIS
My first hypothesis was that a streamlined shape would have the least
amount of drag.
My second hypothesis was that a cube like shape would have the most
drag.
I based my hypothesis on Microsoft Encarta as it stated “A conical shape
will have the least amount of drag because of it’s streamlined shape. ”
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EXPERIMENT DESIGN
The constants in this study were:
* The material the shapes were made out of.
* Time shapes were in wind tunnel.
* Speed of wind.
* Testing procedures.
* The wind tunnel used.
* The weight of shape.
* The spring scale used.
The manipulated variable was the different shapes.
The responding variable was the amount of drag.
To measure the responding variable I determined how much the object
pulled on the spring scale.
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MATERIALS
QUANTITY ITEM DESCRIPTION
2
right triangles from a 2’ x 2’ square, cut from. 75” plywood
1
20” by 20” board
16
6 x 1. 5 screws
28
6 x. 75 screws
12
Angle Brackets
1
roll of clear packaging tape
1
roll of electrical tape
4
blocks of wood
2
Leaf blowers
2
pieces of plastic
1
Short pipe 14” in diameter
1
Short pipe 16” in diameter
1
Short pipe 18” in diameter
1
Pipe 12” in diameter
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PROCEDURES
1. Building the wind Tunnel
a. Align metal pipe to center of 58cm x58cm plywood
b. Screw the metal pipe in to the wood
c. Screw the wooden angles to the side for support
d. Make hole in metal pipe for test section window
e. Put in window for test section
f. Cut hole for leaf blower
g. Steady one leaf blower in the hole
2. Obtain Shapes
a. Buy 4 Styrofoam shapes a sphere, cube, cone, and egg.
3. Experiment
a. Label sphere shape 1.
b. Label cube shape 2.
c. Label cone shape 3.
d. Label egg shape 4.
e. Put shape 1 into the middle of the wind tunnel horizontally.
f. Test shape for 15 seconds.
g. Record how much drag shape 1 had.
h. Turn off leaf blower.
i. Repeat steps 5-8 for trials 2-4.
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RESULTS
My first hypothesis was that a streamlined shape would have the least
amount of drag.
My second hypothesis was that a cube like shape would have the most
drag.
The results of the experiment were that the conical shape had the least
amount of drag 5. 4 grams and the cubic shape had the most drag 21. 4 grams.
See my table and graph and table
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CONCLUSION
My first hypothesis was that a streamlined shape would have the least
amount of drag.
The results indicate that my first hypothesis should be accepted because
the streamlined shape had the least amount of drag
My second hypothesis was a cubic shape would have the most.
My second hypothesis should be accepted because the cubic shape had
the most drag.
Because of the results of this experiment, I wonder if it would give
me different results if I had used twice as much wind speed.
If I were to conduct this project again I would have done more trials
to collect more data. I would have tried different material to build
the shapes.
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RESEARCH REPORT
Introduction
People need transportation to get to work and visit different countries.
Airplanes have helped people for many years and made it a lot easier to
travel around the world. Aerodynamics is helping engineers improve
our flying technology by studying planes in wind tunnels. Every type
of plane is studied in a wind tunnel to make sure that they are safe.
They also test buildings to see if they are stable and can withstand extreme
weather. Vehicle shapes are tested to find out how much drag and
lift they have.
The Four Forces of Aerodynamics
The four aerodynamic forces consist of lift, drag, thrust and gravity.
Drag is created by friction with molecules in the air. Thrust is
the force that moves an object forward. It is created by engines
or motors. Gravity is the force that pushes you down when you jump.
It doesn’t have a big effect on vehicles but it can have an effect on planes.
Bernoulli’s principle explains how air pressure produces lift.
Lift
Lift is the force that keeps an object moving through the air.
This does not have much effect on land and water vehicles. It mostly
has an effect on planes. Lift is what helps planes and birds stay
in the air. Lift has to be greater than gravity for a plane or bird
to fly. Vehicles on land and sea don’t need lift or use it.
Lift is important in land vehicles, mostly because designers want to avoid
it. If a car becomes airborne, that is very dangerous.
Drag
Drag is the force that slows things down. It is a type of friction.
The streamlined shapes are the ones with less drag. They move smoothly
through the air. Wind tunnels can find how much drag a shape has
by watching the air in a wind tunnel. You don’t notice the air’s
drag when you sprint, walk and jog. You can feel the force of drag
when you try to run through water. Dolphins and fish have a streamlined
shape to help reduce drag. There is more drag in water because it
is denser than the air. If we were all as small as insects, drag
would have a big affect. If air was as dense as water we would need
to build different types of shapes so that it would not create too much
drag. They would probably be almost like submarines. The faster
a vehicle goes the more drag becomes a problem.
Thrust
Every vehicle uses thrust. Thrust is what makes the vehicle move forward.
Every object moving needs thrust to move from one place to another, it
is our transportation. Thrust comes from engines or motors. The vehicles
on land, sea and air always use thrust. Thrust has to be greater
than drag to move forward. The engines or motors power the vehicle
and move the axles, which turn the wheels. Then it moves forward
which is thrust.
Gravity
Gravity is the force that draws an object toward the ground. It
offsets lift on a plane and pulls you down when you jump. It does
not have as big an affect on cars as it does on things flying, but it still
has a large effect. Gravity helps with most things like keeping us
from floating into space. It is the force that keeps a vehicle on
the ground. Gravity is good because it gives the vehicle traction
on the ground. The more massive a vehicle is, the more gravity pulls
it toward the ground.
Summary
In conclusion we need thrust for every vehicle it is what makes the
vehicle move forward. Gravity is also important because it
keeps the vehicle from going airborne. Drag is the only problem that
gets in engineers ways that is what they are trying to prevent. Lift
is not very important to land vehicles but it is to planes. The four
forces are all there is and 3 help.
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BIBLIOGRAPHY
“Aerodynamics,” Beginners guide to aerodynamics
http://www. grc. nasa. gov/www/k-12/airplane/fuesalage.htm
“Aerodynamics,” ENCARTA Encyclopedia Deluxe, 2001
“Aerodynamics,” Forces of flight http://www. gomilpitas. com/homeschooling/explore/flight.htm
“Aerodynamics,” Force http://www. allstar. fui. edu/
“Car Design,” ENCARTA Encyclopedia Deluxe, 2001
Dine, Michael. "Force," World Book Encyclopedia, 2002.
Plotkin, Allen. “Aerodynamics,” World Book Encyclopedia, 1999
“Wind Tunnels,” How to build a wind tunnel
http://ldaps. arc. nasa. gov/Curriculum/cheap_tunnel/winddir.html
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ACKNOWLEDGEMENTS
I would like to thank the following people for helping make my project
possible.
* My parents for helping build the wind tunnel and obtaining a lot
of supplies.
* Mr. Newkirk for helping me with everything in my project.
* Mrs. Helms for helping out in class and for fixing a few errors in
my report.
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