Ultra low drag vehicles

[JulianEdgar]

Originally Posted by freebeard

Are we talking about Permalink #30. If so, then get stuffed.

I was pushing back against The Template long before you were around. The difference is I attack the concept, not the person. You mis-read a request for clarification.



Di I push back on that? I think there is some correlation.



So what is fineness ratio again?

Yes I was talking about you. As is so often the case, people read what Aerohead writes, and try to make sense of it, so further causing confusion. Just as you did, introducing a concept (fineness ratio) that has absolutely nothing to do with Reynold's numbers but attempting to build something on the error (area) that Aerohead had just introduced. It won't surprise me at all if people here now link 'fineness ratio' with 'Reynold's Number' - despite what the Reynolds Number equation actually shows!

Just as in another thread, someone asked about BSFC in throttle stop testing, directly following the misleading information Aerohead had just posted. (BSFC has zero to do with throttle stop testing, but again, I bet people will bring it up in the future, such is the nature of misleading information Aerohead posts.)

It really is fascinating how Aerohead causes confusion in others - and even more fascinating, how despite the direct link being obvious, people bristle when the connection is shown.

[freebeard]

As is so often the case, people read what Aerohead writes, and try to make sense of it... Just as you did, introducing a concept (fineness ratio) that has absolutely nothing to do with Reynold's numbers but attempting to build something on the error (area) that Aerohead had just introduced. It won't surprise me at all if people here now link 'fineness ratio' with 'Reynold's Number'

Well then, we'll just point and laugh at them putting an apostrophe in Reynolds number.

[aerohead]

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?

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.

[freebeard]

I think freebeard and I were discussing 'laminar' bodies.

Except I was channeling Dr. Bronner's 'All-One!' philosophy.

[aerohead]

Originally Posted by freebeard

Except I was channeling Dr. Bronner's 'All-One!' philosophy.

Is that the same Dr. Bronner's who's Peppermint liquid soap gave me experiences in the bath which can't be mentioned ?