Quote:
Originally Posted by Vman455
I suppose you could make an argument that frontal area and length are correlated, but even that is only generally true. Take a car like the Smart Fortwo (A = 21.0 square feet) and the original Honda Insight (A = 19.8 square feet) and it falls apart; the Smart is only 106" long while the Honda is 155".
In vehicle aerodynamics we're restricting Reynolds number calculations to incompressible flow; once you introduce things like compressibility and heat flux there are many, many other ways to calculate it. Perhaps you're thinking of one of those?
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I think freebeard and I were discussing 'laminar' bodies.
As a member of the IHPVA I've had occasion to spend days with 'designer/builders' and university teams from all over the globe.
Since these vehicles have human 'engines', and they're typically Olympic-quality athletes, when their racing bike is designed, it's from the 'rider out.'
Since they all lean towards 'laminar' profiles, and laminar profiles are Rn-dependent, there's an impetus to minimize Af. While a profile can be scaled up or down, the relationship between width or height, and total length must be maintained as a constant.
The minimum Af provides the minimum length, which directly affects Rn, and just allows enough interior volume to contain the rider. In this way, they keep the bike at sub-critical Rn as best they can.
This is the context for our back and forth.
You're totally correct to react the way you have. And your logic is spot-on.
I cringe whenever the topic of 'laminar' bodies comes up, for the very reasons we're having this conversation.
