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Old 09-17-2013, 02:17 PM   #71 (permalink)
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kach22i -- Six posts between [Yesterday, 05:43 PM] and [Yesterday, 06:25 PM]. You're a machine.

I like the '32 Ford front suspension w/ leading arm torsion bars and centered steering box. I wonder what that front tire size is though.

I'll be looking at the Roger Wood story to find out what is said about 'passive porosity'. The underbody diagams in #68 and cfd_guy's #69 are helpful.

cfd_guy -- A is fixed by the vehicles purpose. Cd is a unitless number.


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Old 09-17-2013, 04:42 PM   #72 (permalink)
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Quote:
Originally Posted by freebeard View Post

cfd_guy -- A is fixed by the vehicles purpose. Cd is a unitless number.
Yes I know but CdA is a better number to use to associate to fuel mileage from the force or drag.
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Old 09-17-2013, 08:02 PM   #73 (permalink)
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As for the Volvo link : only the C30 Drive / coupe version got the belly panels, not the rest of the range.
From personal experience, I doubt very much the - awfully heavy - aerodynamic wheels ever helped its mileage much.

The Hyundai underside shot is bogus, showing the flow to be nicely lengthwise underneath.
It gets pushed out sideways.
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Old 09-18-2013, 02:21 AM   #74 (permalink)
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Quote:
Originally Posted by myself
I'll be looking at the Roger Wood story to find out what is said about 'passive porosity'.
Interesting article. Some observations:
  • Reynolds number is important in interpreting wind tunnel results and explains why little stick-on tabs won't affect the air around a larger vehicle.
  • Roll- up door instead of swing door equals free box cavity.
  • "The sides and top of a trailer do not generate pressure drag, not even in crosswinds."

As for passive porosity, I found:
Quote:
Originally Posted by Google
[PDF] SIMULATION OF FLOWS WITH PASSIVE POROSITY - ICAS is
http://www.icas.org/ICAS_ARCHIVE/ICA...102.PDF‎
by NT Frink - ‎2002 - ‎Cited by 2 - ‎Related articles
ICAS 2002 CONGRESS. 2102.1. SIMULATION OF FLOWS WITH PASSIVE POROSITY ... International Council of the Aeronautical Sciences, with permission
I hope they don't mind my sharing this:


It's pretty exciting. My panel van will have a full PolyMetal bellypan and a boattail made from Goodwill trampolines.
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Old 09-18-2013, 03:41 PM   #75 (permalink)
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This is where so-called wind tunnel pictures "jump the shark".

Blue Sports Car In A Wind Tunnel
Blue Sports Car In A Wind Tunnel Photograph by Mark Evans - Blue Sports Car In A Wind Tunnel Fine Art Prints and Posters for Sale


Claims it's a "photograph" but looks like a computer rending.

Say's "Blue Sports Car In A Wind Tunnel", but what make of car is that supposed to be?

Faking CFD is one thing (it's all conjecture at some level), but this crosses the line.

.................................................. .........................

Someone talked of "dust" being a real-life indicator.

Does this one qualify?

Aerodynamics on Land: Aiming for 800 M.P.H..............2009
http://www.nytimes.com/2009/04/21/sc...anted=all&_r=0
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Old 09-19-2013, 03:21 AM   #76 (permalink)
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This one did it for me. I'm not buying the flow over the hood.

OTOH confirmation bias allows me to totally accept the passive porosity thing.
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Old 09-19-2013, 01:17 PM   #77 (permalink)
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Quote:
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This one did it for me. I'm not buying the flow over the hood.
It's looks quite normal to me.

This one below puzzles me to no end.

Rocket Car Design Project
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Old 09-20-2013, 03:33 AM   #78 (permalink)
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Quote:
It's looks quite normal to me.

This one below puzzles me to no end.
It looks to me like there's a series of progressively larger bug deflectors on the hood. Doesn't the high pressure bubble at the base of the windshield have air circulating through it instead of being a locked vortex?

The one 'below' shows the area that is in magenta here.

This is why the bubble top vanagon has better air flow than the pop-top.

Check the numbers.

I wish I could find pictures of Beetles racing in the rain. There's a water roostertail about 6 feet high off the windshield.
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Old 09-24-2013, 09:54 AM   #79 (permalink)
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1939 Maybach Stromlinienkarosserie:



This shows that air flows up from under the car and it flows around to the top, behind the rear wheels. And this would be addressed by having a narrower rear wheel track.

The Schlörwagen has a similar issue, though the solution there might be to widen the tail into a "beaver tail":

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Old 09-25-2013, 02:37 PM   #80 (permalink)
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How about a random Cd chart tossed in?

Several pages of Hucho's book are in the link.

Threshold Strategy - Halving the Drag Coefficient Seems Possible - ATZ online

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