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Old 02-09-2012, 12:55 AM   #231 (permalink)
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Old 02-09-2012, 03:09 AM   #232 (permalink)
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Old 02-09-2012, 06:20 AM   #233 (permalink)
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Old 02-11-2012, 03:35 PM   #234 (permalink)
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US NAVAL AERO photo

Here's the flow separation photo from the AERODYNAMICS FOR NAVAL AVIATORS book
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Old 02-11-2012, 04:15 PM   #235 (permalink)
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Quote:
Originally Posted by aerohead View Post
Here's the flow separation photo from the AERODYNAMICS FOR NAVAL AVIATORS book
Looks like a wheel fairing or something of that ilk. So I guess the message is that the thing could have just been truncated at the separation point with no increase in drag?
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Old 02-11-2012, 04:42 PM   #236 (permalink)
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truncated

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Originally Posted by jimepting View Post
Looks like a wheel fairing or something of that ilk. So I guess the message is that the thing could have just been truncated at the separation point with no increase in drag?
That's what the Big Boys would say.The 'phantom' tail.
I am curious about crosswind conditions though.
I rotund 18-wheeler can see a minimum of 1.63 X drag increase in 20-degree crosswind.
Looking at Cd's document on the 1996 HONDA Dream,a 15-degree crosswind yaw condition will cause only a 25% drag increase for the 'pumpkin seed.'
So maybe stuffing the wake has a benefit in wind,and the wind seems to blow all the time around here!
It would make a good wind tunnel investigation.
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Old 02-11-2012, 06:16 PM   #237 (permalink)
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Don't know just how relevant, but came across a Highway Crosswind Calculator for trucks and other high profile vehicles.

A contributor with deep knowledge of truck fleet operations (and international engine consultant), Doug Hilary, (on BITOG) states that 3/4'ng headwinds are much the worst for FE.
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Old 02-12-2012, 11:01 PM   #238 (permalink)
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Re: the template - where are the vertical % to match the horizontal %? In other words, what are the X and Y coordinates for the template? Does the spline have an equation?

Doesn't the data show that an ellipsoid has virtually the same Cd as the teardrop?

What's the Cd down to 55% template? This is where I see a pickup terminating. It'd be handy to determine point of diminishing returns.

I've observed snow on my car. I hypothesize that sharp corners discourage atmospheric pressure side air from moving towards the lower pressure area above the car, and reduces vortices. If no vortices are created above the roof, then it's even less likely imo to create vortices at the trunk edge. I think that a polyellipsoid reduces the lateral pressure gradient - which also prevents vortices.
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Old 02-13-2012, 01:03 AM   #239 (permalink)
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I couldn't wait.

I scaled the template and input it into a 3D program. It's a few percent squatter, and I'm happy with the resolution and accuracy (especially since most forms will be truncated where it's a better approximation).

So...now I have to figure out how to CFD test it.

I'd love to make up a bed cap for my dad's Sierra 1500.
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Old 02-14-2012, 08:48 AM   #240 (permalink)
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Quote:
Originally Posted by ERTW View Post
I couldn't wait.

I scaled the template and input it into a 3D program. It's a few percent squatter, and I'm happy with the resolution and accuracy (especially since most forms will be truncated where it's a better approximation).

So...now I have to figure out how to CFD test it.

I'd love to make up a bed cap for my dad's Sierra 1500.


ERTW, that's interesting. I've been drooling to see CFD on the streamline template and other gold standards.

Phil can correct me but it's supposed to be a body of revolution. From top view the nose should be rounded and sides taper. Think missile or torpedo.

Rock on!

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