new to list...98 A4 1.8T
10-28-2001, 06:56 AM
#19
AudiWorld Senior Member
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Silver really is the fastest color. I'm not kidding - here's why...
This may have been posted before, but according to AOA, silver is the fastest color because dealers report that silver Audis move the fastest off their lots = they sell first before any other color.
10-28-2001, 07:09 AM
#20
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Re: Silver really is the fastest color. I'm not kidding - here's why...
"PHYSICAL CHARACTERISTICS OF COLOR "
"The color that provides the least skin friction drag is black. Black also helps prevent separation of the laminar boundary layer. "
"The aerodynamic book "Theory of Wing Sections", page 109, written by Ira H. Abbott and Albert E. Von Doenhoff, explains that skin friction for an object (soap box racer) that absorbs no heat from the free stream is, lets say 1.330. The skin friction for a soap box that is 1/4 the absolute temperature of the free stream is 1.420 at 50 miles per hour. This means that the laminar skin friction increases with heat transfer from the fluid (surrounding air) to the surface of the racer. This increase is small even for the extremely low racer temperatures. This means that the surface temperature of the racer should be as hot as possible. The color of the racer should be one that absorbs as much heat as possible from the sun. This color is black!"
"Another aerodynamics book, "Boundary Layer Theory', written by Dr. Hermann Schlichting, page 467, explains how heat transfer to and from the surface wall (surface of racer) affects the transition of the laminar boundary layer to a turbulent boundary layer, causing more aerodynamic drag. heat transfer from the surface to the fluid (air) at VERY HIGH SPEEDS (Mach 2 and above) has a destabilizing effect on laminar boundary layer flow, but at low speeds the reverse is true. Therefore' a racer going 30 miles per hour with a hot surface (compared to the ambient air temperature) will have a more stabilizing effect on the boundary layer, thereby causing less air drag, and a faster racer. Again black is the best color. "
"In 1949, Fred Derks, of Akron, figured it all out with a complicated system of calculating heat, pressure, and resistance. He raced a black car and won handily". (Popular Science, May 1952). "
Tony Carlini, Sr.
"The color that provides the least skin friction drag is black. Black also helps prevent separation of the laminar boundary layer. "
"The aerodynamic book "Theory of Wing Sections", page 109, written by Ira H. Abbott and Albert E. Von Doenhoff, explains that skin friction for an object (soap box racer) that absorbs no heat from the free stream is, lets say 1.330. The skin friction for a soap box that is 1/4 the absolute temperature of the free stream is 1.420 at 50 miles per hour. This means that the laminar skin friction increases with heat transfer from the fluid (surrounding air) to the surface of the racer. This increase is small even for the extremely low racer temperatures. This means that the surface temperature of the racer should be as hot as possible. The color of the racer should be one that absorbs as much heat as possible from the sun. This color is black!"
"Another aerodynamics book, "Boundary Layer Theory', written by Dr. Hermann Schlichting, page 467, explains how heat transfer to and from the surface wall (surface of racer) affects the transition of the laminar boundary layer to a turbulent boundary layer, causing more aerodynamic drag. heat transfer from the surface to the fluid (air) at VERY HIGH SPEEDS (Mach 2 and above) has a destabilizing effect on laminar boundary layer flow, but at low speeds the reverse is true. Therefore' a racer going 30 miles per hour with a hot surface (compared to the ambient air temperature) will have a more stabilizing effect on the boundary layer, thereby causing less air drag, and a faster racer. Again black is the best color. "
"In 1949, Fred Derks, of Akron, figured it all out with a complicated system of calculating heat, pressure, and resistance. He raced a black car and won handily". (Popular Science, May 1952). "
Tony Carlini, Sr.