1. The Effect of Dimpling on the Drag Force of an Automobile in Motion
Josh Denzler – Lake Shore High School
Mike Oliver – Lake Shore High School

2. Terminology Drag Force – A force that opposes a projectile’s motion
Wake – Area of turbulent air behind a projectile
Dimple – A slight depression

3. Background Gas Prices: Have risen in recent years New Standards:
“that will increase fuel economy to the equivalent of 54.5 mpg for cars and light-duty trucks by Model Year 2025”

4. Background Car companies: Making more fuel efficient cars
Hybrid technology
Lightweight materials
Aerodynamics
More aerodynamic = less energy to move car
Less energy to move car = less fuel consumed

5. Scientific Concepts Dimpling: Improves aerodynamics of a golf ball
Can it improve the aerodynamics of a car?

6. Previous Research Mythbusters: Zipp:
Ran an identical course with dimpled and smooth cars
Saw a fuel efficiency increase of three mpg
Zipp:
Bicycle manufacturer
Dimples surface of their disk wheels
Better gripping ability on the roads
Takes less effort to spin the tire

7. Previous Research Fastskinz: Dimpled vinyl skin to go over cars
Tested by Popular Mechanics:
Did not improve fuel efficiency

8. Problem
Do different dimple sizes on a car reduce the drag force acting on that car?

9. Hypothesis
The smooth car, six millimeter dimple, eight millimeter dimple, and ten millimeter dimple will not all have equal drag forces
The ten millimeter diameter dimple will result in the largest reduction of drag.

10. Materials
Wind Tunnel
Vernier Lab Quest
Asus Tablet
Lab Car Model

11. Procedure
We are going to insert a video of our procedures here. We will narrate the video appropriately while it is playing.

12. Sample Data Value Drag Force (N) Smooth Car 6 mm Dimple Car
High
0.178
0.230
0.200
0.268
Low
.071
0.090
0.012
0.052
Average
0.123
0.140
0.074
0.151

13. Smooth Car Observations
Trial
Observation 2
String fell off of pulley, trial redone. 3
Car went back before Lab Quest could get data, trial redone 4
Trials 1-4 were abnormal values and were redone. 6
Abnormally small value, trial redone 11
Abnormal graph of data, data kept 12 13 15
Car did not move, trial redone 16
23, 24 27

14. 6 mm Dimple Car Observations
Trial
Observation 8
Car did not move, trial redone 12 19

15. 8 mm Dimple Car Observations
Trial
Observation 8
Second fan not started on time, trial redone 14
Car did not move, trial redone 15 21 22
String fell off of pulley, trial redone. 23

16. 10 mm Dimple Car Observations
Trial
Observation 2
Car went back before Lab Quest could get data, trial redone 7
String fell off of pulley, trial redone.
8, 10, 12, 15
Car did not move, trial redone 21
Abnormally small value, trial redone 29 30

17. Data Analysis and Interpretation

18. Data Analysis and Interpretation

19. Data Analysis and Interpretation

20. Data Analysis and Interpretation

21. Data Analysis and Interpretation

22. Data Analysis and Interpretation

23. Conclusion
Purpose:
To find out if dimples had an effect on the drag force acting on a car
To find which dimple size has the greatest effect on that drag force

24. Conclusion The Experiment: Used a force sensor
Compared drag force acting on different car types
Used ANOVA and Two-Sample t Tests
Found 8 mm dimple car to have lowest drag force of all car types

25. Conclusion Initial Hypothesis:
The smooth car, six millimeter dimple, eight millimeter dimple, and ten millimeter dimple will not all have equal drag forces
The ten millimeter diameter dimple will result in the largest reduction of drag

26. Conclusion Hypothesis Rejected: Why?
All cars did not have same drag force
BUT 8 mm car had the lowest drag force
Why?
A car is not a golf ball
Air is not flowing around the car uniformly
Design Flaws

27. Design Flaws Bad Dimpling: Data Not Randomized:
Dimples not uniform distance apart
Dimples went too far into clay
Machine would be more accurate
Data Not Randomized:
Lurking variables would affect data unevenly
Monetary resources
Machine could also correct this

28. Further Research Different Patterns: Other forms of transportation:
Different dimples (hexagon, square, etc)
Planes
Trains
Troughs/Ridges
Ships
Different Car Style:
Less sports car like
More ball-shaped

29. Real Life Application Automotive Design: Projectile Design:
More fuel efficient cars
Decrease oil dependency
Help conform to Obama’s standards
Projectile Design:
Bullets, missiles, balls, etc.
Reduces energy needed to fly
Can fly further/longer

30. Any Questions?