the effect of dimpling on the drag force of an automobile in motion
DESCRIPTION
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. Terminology. Drag Force – A force that opposes a projectile’s motion Wake – Area of turbulent air behind a projectile - PowerPoint PPT PresentationTRANSCRIPT
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
Terminology
• Drag Force – A force that opposes a projectile’s motion
• Wake – Area of turbulent air behind a projectile
• Dimple – A slight depression
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”
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
Scientific Concepts • Dimpling:
– Improves aerodynamics of a golf ball– Can it improve the aerodynamics of a car?
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
Previous Research
• Fastskinz:– Dimpled vinyl skin to go over cars– Tested by Popular Mechanics:
• Did not improve fuel efficiency
Problem
• Do different dimple sizes on a car reduce the drag force acting on that car?
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.
MaterialsWind Tunnel
Vernier Lab Quest
Asus TabletLab Car Model
Procedure
• We are going to insert a video of our procedures here. We will narrate the video appropriately while it is playing.
Sample Data
Value
Drag Force (N)
Smooth Car
6 mm Dimple Car
8 mm Dimple Car
10 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
Smooth Car ObservationsTrial 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 Abnormally small value, trial redone
13 String fell off of pulley, trial redone.
15 Car did not move, trial redone
16 Car did not move, trial redone
23, 24 Car went back before Lab Quest could get data, trial redone
27 Car did not move, trial redone
6 mm Dimple Car Observations
Trial Observation
8 Car did not move, trial redone
12 Car did not move, trial redone
19 Car did not move, trial redone
8 mm Dimple Car ObservationsTrial Observation
8 Second fan not started on time, trial redone
14 Car did not move, trial redone
15 Car did not move, trial redone
21 Car did not move, trial redone
22 String fell off of pulley, trial redone.
23 String fell off of pulley, trial redone.
10 mm Dimple Car ObservationsTrial Observation
2Car 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 Car did not move, trial redone
30 Abnormally small value, trial redone
Data Analysis and Interpretation
Data Analysis and Interpretation
Data Analysis and Interpretation
Data Analysis and Interpretation
Data Analysis and Interpretation
Data Analysis and Interpretation
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
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
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
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
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
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
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
Any Questions?