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testing aero. of a caravan

Ran across these on You-Tube:
https://www.youtube.com/watch?v=karGqjCZOV8

Thats a very dirty wake. Must be room for huge improvement

Quote:

Originally Posted by chefdave (Post 494012)

Thats a very dirty wake. Must be room for huge improvement

NASA says kill the gap,then boat tail it.

Would a kammback help if boat tail is too long

What about that "part 2" video with the topper? Is that better or worse?
https://youtu.be/sweZltfD-no

I'd go with different. They missed a bet not putting the two videos one above the other and matched in speed.

It's interesting to watch the lines approach from the left. There's some initial noise that damps down to straight lines, but they aren't erased so it obscures the initial approach. There appears to be turbulence building up ahead of the rooftop container, it might be caused by the airgap between the topper and roof.

The topper seems to create a locked in rolling vortex ahead of the trailer, similar to a half-tonneau cover on a pickup.

What do you think about the area above and behind the trailer? With the container the disturbed air rises higher, even out of the rendered flow lines, but it looked somehow more orderly to me.

Quote:

Originally Posted by chefdave (Post 494020)

Would a kammback help if boat tail is too long

Technically speaking,a K-form tail (Kamm-back) is just a shortened ideal tail (boat-tail),or vice versa.
Here you can see how Koenig-Kamm experimented with different lengths of this K-form at the FKFS,next door to Daimler-Benz in Stuttgart.
http://i1271.photobucket.com/albums/...titled5_17.jpg

Quote:

Originally Posted by Hersbird (Post 494033)

What about that "part 2" video with the topper? Is that better or worse?
https://youtu.be/sweZltfD-no

My gut feeling is that this is a low-cost,2-dimentional CFD program,that they don't achieve a critical Reynolds number flow,and while interesting to watch,and trends may be reflected,we'd want an expensive,corporate-level,3-D program to provide a more real-world representation of how things would be.
I don't think the streamline filaments would behave the way they're depicted.

above and behind

Quote:

Originally Posted by freebeard (Post 494039)

After watching it, YouTube offered up this gem:
https://www.youtube.com/watch?v=0577mRifVfI

Improved aero over most trailers, but the really interesting thing is the hydraulic lowering by rotating the entire suspension assembly.