Automobile
Aerodynamics
Table of Contents
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Introduction
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Principles of Aerodynamics
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Historical Milestones
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Aerodynamic Components in Action
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Performance Impacts
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Case Studies
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Questions
Aerodynamics is the study of the behavior of gaseous fluids as they
interact with objects in motion, particularly focusing on the forces
exerted on these objects.
In the realm of automobile racing, where fractions of a second can
determine victory or defeat, a nuanced understanding of
Introduction
aerodynamics is crucial for optimizing vehicle speed, stability, and
fuel efficiency, thereby providing teams with a competitive edge on
the track.
Streamlining
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Curves associated with the fluid motion of air particles
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Attached, laminar flows are important in reducing drag & increasing downforce
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Flow separation creates unsteady wake flows and increases the drag force
The Boundary Layer
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Object in motion disturbs air particles as they move around the object
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Creates an offset of air particle velocity in the space surrounding the object
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Thicker boundary layers can create more air drag
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A dramatic increase in boundary layer thickness causes flow separation (very high drag)
Form Drag
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Determined by the size and shape of the vehicle body
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Can act horizontally and/or vertically
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High pressure at the front of the vehicle and low pressure above and directly behind it
Skin Friction
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Determined by air resistance as the vehicle moves through it
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Acts Parallel to the body’s surface
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More favorable than form drag
Primary Aerodynamic Forces
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Drag is dependent on a combination of form drag & skin
friction
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Lift is produced by form drag at high speeds
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Lateral force is caused by wind moving in lateral directions or
non symmetrical design
Shape Optimization
1921 Tropfenwagen
Prototype
1950 Porsche 356
2023 AMG 1
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Increases in vehicle speed capabilities has required manufacturers to optimize vehicle shape
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1920s: Prioritized reduction of form drag by narrowing the body
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1950s: Prioritized streamlining and vehicle height
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Today: Prioritizing ground clearance & downforce
Terminology
Bumper
Undercarriage
Rear/ Back
Splitter
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Optimal 4-5 inches
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High pressure area above the splitter
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Difference in air pressure generates
downforce
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Streamline airflow to the undercarriage
Adding a Splitter
Bumper
Splitter
Undercarriage
Rear/
Back
Undercarriage
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Smoother air flow
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Consistent air pressure
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Protection against bottoming out
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Fuel efficiency
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Works in combination with the diffuser
Modern cars
Adding a Shield/Cover
Bumper
Rear/ Back
Splitter
Undercarriage
Shield/Cover
Venturi Effect
Reduction in pressure as fluid passes through a
constricted are and the subsequent increase in
pressure as it exits into an expansion chamber
Diffuser
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Generates downforce by acting as an expansion
chamber
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Venturi effect
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Angle of the diffuser must be 7.5 degrees or less
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Needs significant airflow to work well
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If boundary layer separates it can create drag
Adding a Diffuser
Bumper
Rear/ Back
Splitter
Undercarriage
Diffuser
Shield/Cover
Historical Performance Impacts
Case Studies
The End
Citations
Ono, Alto. “Slipstream and ‘dirty Air’ Explained.” Racecar Engineering, 31 July 2020,
www.racecar-engineering.com/tech-explained/slipstream-and-dirty-air-explained/.
Roberts, Neil. “Air Dams, Splitters, Spoilers and Wings - Downforce Increases Grip, Grip Decreases Lap Times,
and Isn’t That the Whole Point?” NASA Speed News Magazine, 4 Feb. 2019,
nasaspeed.news/tech/aero/air-dams-splitters-spoilers-and-wings-downforce-increases-grip-grip-decrea
ses-lap-times-and-isnt-that-the-whole-point/.
Toet, Willem. “Willem Toet Explains....Motorsport Diffusers: Race Tech Magazine.” Race Tech Magazine |, 28
Jan. 2019, www.racetechmag.com/2017/08/willem-toet-explains-motorsport-diffusers/.