Quote:
Originally Posted by wax87
I am new to all of this, Is the optimum curvature a function of the speed that you want to travel at or is it pretty universal for automobiles?
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For road vehicles, and between 20-mph, and 250-mph, and because of the relationship between their length and speed, the coefficient of aerodynamic drag, Cd [ based on the vehicles frontal projected area ( the size of the imaginary hole it burrows though the air, as measured by the shadow it casts from a coherent light source from ahead, projected onto a screen behind it )] remains constant.
A long way of saying that, no, it doesn't change, regardless of shape.
Technically, it has satisfied it's 'critical Reynolds number' criteria for constant Cd ( because of a turbulent boundary-layer, and because the air will remain incompressible throughout this velocity range ).
The 'optimum' curvature ( contour / silhouette ) IS the major defining factor of the Cd. It has to do with boundary-layer theory and effective fineness ratio.