Josh Denzler Lake Shore High School Mike Oliver Lake Shore High School Terminology Drag Force A force that opposes a projectiles motion Wake Area of turbulent air behind a projectile ID: 265437
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Slide1
The Effect of Dimpling on the Drag Force of an Automobile in Motion
Josh
Denzler
– Lake Shore High School
Mike Oliver – Lake Shore High SchoolSlide2
Terminology
Drag Force – A force that opposes a projectile’s motion
Wake – Area of turbulent air behind a projectile
Dimple – A slight depressionSlide3
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” Slide4
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 consumedSlide5
Scientific Concepts
Dimpling:
Improves aerodynamics of a golf ball
Can it improve the aerodynamics of a car?Slide6
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
B
etter
gripping ability on
the roads
Takes
less effort to spin the
tire Slide7
Previous Research
Fastskinz
:
Dimpled vinyl skin to go over cars
Tested by
Popular Mechanics
:
Did not improve fuel efficiencySlide8
Problem
Do different dimple sizes on a
car
reduce the drag force acting on
that
car? Slide9
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
.Slide10
Materials
Wind Tunnel
Vernier
Lab Quest
Asus Tablet
Lab Car ModelSlide11
Procedure
We are going to insert a video of our procedures here. We will narrate the video appropriately while it is playing.Slide12
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
0.151Slide13
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
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 redoneSlide14
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 redoneSlide15
8 mm Dimple Car Observations
Trial
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.Slide16
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
Car did not move, trial redone
30
Abnormally small value, trial redoneSlide17
Data Analysis and InterpretationSlide18
Data Analysis and InterpretationSlide19
Data Analysis and InterpretationSlide20
Data Analysis and InterpretationSlide21
Data Analysis and InterpretationSlide22
Data Analysis and InterpretationSlide23
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 forceSlide24
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 typesSlide25
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
dragSlide26
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 FlawsSlide27
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 thisSlide28
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
ShipsSlide29
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/longerSlide30
Any Questions?