The Effect of Dimpling on the Drag Force of an Automobile in Motion

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: • 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

13. Smooth Car Observations

14. 6 mm Dimple Car Observations

15. 8 mm Dimple Car Observations

16. 10 mm Dimple Car Observations

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

29. Real Life Application • Automotive 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?