Aerodynamic Drag of Several Basic Vehicle Shapes

PURPOSE

The purpose of this experiment was to determine the aerodynamic drag of several basic vehicle shapes.

I became interested in this idea when I was riding in our convertible and I felt the air hit me in the back of the head instead of the front of my head. I wondered why the air was coming from behind me. 

The information gained from this experiment could show designers which shape would be the most aerodynamic. Society would want to build more aerodynamic cars and planes because they are more efficient and would save gas and money.

  

HYPOTHESIS

My first hypothesis was that the hemispherical nose would be the most aerodynamic, having the least amount of drag.

My second hypothesis was that the conical tail would be the most aerodynamic, having the least amount of drag. 

I based my hypothesis on a science project done in 2003 by Landin Arnett, ”The Effect of Different Fuselage Shapes on Drag.” He said, “The hemispherical nose and the conical tail did the best.”

              EXPERIMENT DESIGN

The constants in this study were:

•    The speed of wind

•    The size of wind tunnel

•    The type of wind tunnel

•    The spring scale

•    The type of wheels

•    The size of wheels

•    The main body of the car

•    The source of wind

•    The mass of the car 

The manipulated variables were the shape of the nose and tail. 

The responding variable was the force of drag.  

To measure the responding variable, I used a spring scale to see how much drag force there was in newtons.

                                   MATERIALS

QUANTITY	ITEM DESCRIPTION
2	Hemispherical shapes of Styrofoam
2	Conical shapes of Styrofoam
2	Square shapes of Styrofoam
1	Air tunnel
1	Spring scale
1	Roller
1	Car body
2	Leaf blowers
3cm	string
4”	Wide tube

  

PROCEDURES

1.    Get all of the supplies listed in “materials”

2.    Construct the car and the interchangeable nose and tail pieces

a.    Use nose and tail pieces that are two conical shapes, two hemispherical shapes, and two flat shapes that are cut out of Styrofoam

b.    Each of the shapes must be four inches wide which is the width of the tube

c.  Make sure that the car rolls easily

d.  Build the car low to the ground so that you only see the tires

e.  Don’t let the pipe touch the tires on the roller

3.    Setup the wind tunnel for use

a.    Attach the spring scale to the wind so it wont slide around during the experiment

b.    Tape the spring scale inside the wind tunnel

c.    Put the two leaf blowers together so they can be used

4.    Install the hemispherical shape of Styrofoam for the nose. Then install a conical shape for the tail of the car (the nose and tail do NOT have to be the same but eventually will have to)

5.    Attach the shapes chosen to the car’s nose and tail and place the shapes inside the tunnel 

6. Tie the car to the spring scale with the 3cm string

7. Turn the two leaf blowers on while they are in the wind tunnel

8.  Watch the spring scale closely for force changes

a. This will give you the amount of drag the car produces

9.  Record your observations of the spring scale

10. Watch the car closely for its reaction to the wind 

11.  Record your observations of the car’s behavior 

12. Do each experiment for each set of shapes 5 times

13. Choose another set of Styrofoam shapes for the car’s nose and tail 

14. Repeat steps 4-14 until you run out of shape combinations to use for the nose and tail of the car you made 

15. Record your results of each of the experiments 

a.    Average out how well each nose did with each of the three tails

b.    Average out how well each tail did with each nose

c.    That will tell you which pair of shapes did the best

d.    It will also tell you which pair of shapes did the worst

  

RESULTS

The original purpose of this experiment was to determine the aerodynamic drag of several basic vehicle shapes.

The results of the experiment were that the conical nose and the conical tail section, the conical nose and the hemispherical tail, and the conical nose and flat tail section all averaged 0.00 newtons of drag. Thus, the average amount of drag of the conical tail was 0.00 newtons.

The hemispherical nose along with the conical tail section averaged 0.01 newtons of drag, while the hemispherical nose along with the hemispherical tail section averaged 0.05 newtons of drag, and the hemispherical nose and the flat tail section averaged 0.00 newtons of drag. Thus the average amount of drag in newtons for the hemispherical nose was 0.02.

The flat nose along with the conical tail section averaged 0.33newtons of drag, and the flat nose and the hemispherical tail section averaged 0.16 newtons of drag. The flat nose along with the flat tail section averaged 0.29 newtons of drag. Thus, the average amount of drag in newtons of the flat nose was 0.26.    

CONCLUSION

My original hypothesis was that the hemispherical nose would be the most aerodynamic.

My second hypothesis was that the conical tail would be the most aerodynamic. 

The results indicate that this hypothesis should be rejected, because the conical nose and the hemisperical  tail did the  best, instead of the hemisperical nose and the conical tail.

After thinking about the results of this experiment, I wonder if I used the same shapes in hydrodynamics if the results would be the same. 

I also wonder if  I used the same shapes only as sails if I would get the same results.

If I were to conduct this project again I would use a lighter pipe, different shapes and smoother shapes, a different material for the shapes, and I would do more trials.

Researched by -------Brennan D