Race Car Aerodynamics
Race Car Aerodynamics
Gregor Seljak
April 8, 2008
1
Introduction
First racing cars were primarily designed to achieve high top speeds and the main goal was to minimize the air drag. But at high speeds, cars developed lift forces, which affected their stability. In order to improve their stability and handling, engineers mounted inverted wings profiles1 generating negative lift. First such cars were Opel’s rocket powered RAK1 and RAK2 in 1928.
However, in Formula, wings were not used for another 30 years. Racing in this era 1930’s to 1960’s occured on tracks where the maximum speed could be attained over significant distance, so development aimed on reducing drag and potencial of downforce had not been discovered until the late 1960’s. But since then, Formula 1 has led the way in innovative methods of generating downforce within ever more restrictive regulations.
Figure 1: Opel’s rocket powered RAK2, with large side wings
2
Airfoils
Airfoil can be definead as a shape of wing, as seen in cross-section. In order to describe an airfoil, we must define the following terms(Figure 2)
• The mean camber line is a line drawn midway between the upper and lower surfaces.
• The leading and trailing edge are the most forward an rearward of the mean camber line.
1
Compared to an aircraft
1
• The chord line is a line connecing leading an trailing edge.
• The chord length is the distance from the leading to the trailing edge, measured along the chord line.
• The camber is the maximum distance between mean camber line and chord line.
• The thickness is the distance between the upper and lower surfaces.
Figure 2: Airfoil nomenclature
The amount of lift L produced by the airfoil, can be expressed in term of lift coefficient CL
1
2
(1)
L = ρ∞ V∞ SCL
2
where V∞ denotes the freestrem velocity, ρ∞ fluid density and S the airfoil area. 2.1
Flow over an airfoil
Properties of an airfoil can be measured in a wind tunnel,
Gregor Seljak
April 8, 2008
1
Introduction
First racing cars were primarily designed to achieve high top speeds and the main goal was to minimize the air drag. But at high speeds, cars developed lift forces, which affected their stability. In order to improve their stability and handling, engineers mounted inverted wings profiles1 generating negative lift. First such cars were Opel’s rocket powered RAK1 and RAK2 in 1928.
However, in Formula, wings were not used for another 30 years. Racing in this era 1930’s to 1960’s occured on tracks where the maximum speed could be attained over significant distance, so development aimed on reducing drag and potencial of downforce had not been discovered until the late 1960’s. But since then, Formula 1 has led the way in innovative methods of generating downforce within ever more restrictive regulations.
Figure 1: Opel’s rocket powered RAK2, with large side wings
2
Airfoils
Airfoil can be definead as a shape of wing, as seen in cross-section. In order to describe an airfoil, we must define the following terms(Figure 2)
• The mean camber line is a line drawn midway between the upper and lower surfaces.
• The leading and trailing edge are the most forward an rearward of the mean camber line.
1
Compared to an aircraft
1
• The chord line is a line connecing leading an trailing edge.
• The chord length is the distance from the leading to the trailing edge, measured along the chord line.
• The camber is the maximum distance between mean camber line and chord line.
• The thickness is the distance between the upper and lower surfaces.
Figure 2: Airfoil nomenclature
The amount of lift L produced by the airfoil, can be expressed in term of lift coefficient CL
1
2
(1)
L = ρ∞ V∞ SCL
2
where V∞ denotes the freestrem velocity, ρ∞ fluid density and S the airfoil area. 2.1
Flow over an airfoil
Properties of an airfoil can be measured in a wind tunnel,