Silverado aerocap build thread

[round.boater]

Originally Posted by MetroMPG

Bondo (Brett) has added a small window (presumably lexan or equivalent) to the top of his aerocap. You might want to ask him whether it's functional to the driver or not.

The window is totally functional while driving. It's also been fun this winter to watch the snow stream past the window with the attached airflow...

And as an added bonus, when we're camping in the shell we now have a way to look at the stars. We used to sleep with heads towards the front, now we go in feet first to look up through the window!

[MetroMPG]

To keep this thread on topic, I'm going to split the discussion about whether a "traditional" boxy camper is more aerodynamic (vs. none) into a new thread. Coming up shortly...

Discussion moved here: http://ecomodder.com/forum/showthrea...age-11807.html

[winkosmosis]

Amazon.com: Johnson Level & Tool and Tool 700 Magnetic Angle Locator: Home Improvement

[sleeeper]

Haven't seen this one discussed but is very interesting data for these aeroshells, the velocity and vector figures on page 6 and 7 are easier to understand than the rest:

Experimental Investigation of the Near Wake of a Pick-up Truck

https://eprints.kfupm.edu.sa/453/1/2003_01_0651.pdf

The horizontal view shows some serious eddies forming from the sides of the bed too

[aerohead]

Originally Posted by sleeeper

Haven't seen this one discussed but is very interesting data for these aeroshells, the velocity and vector figures on page 6 and 7 are easier to understand than the rest:

Experimental Investigation of the Near Wake of a Pick-up Truck

https://eprints.kfupm.edu.sa/453/1/2003_01_0651.pdf

The horizontal view shows some serious eddies forming from the sides of the bed too

If they'd gone back a few more years in their research they would have found the Texas Tech SAE Paper and some of D.P.Jordan's CFD work which looks remarkably similar.
Also,in the FLOW-IMAGES Gallery you'll find the blue streamline reverse-step image.By just following the streamlines you can design your cover.

[sleeeper]

I wonder about practical strategies to reduce the horizontal component of the trailing eddies behind the tailgate. Maybe some clear vertical Kamback style panels running along the back corners of the bed (taillights) would help kinda like the side portion on the Mooncraft Prius. I also wonder about using a rear belly pan to encourage some of the under-truck flow to exit in the center to counter act the forward component of the eddies.

[ChazInMT]

You're doomed here with regard to horizontal swirling behind the tailgate, every vehicle has this in the back just about. The only way to get rid of it is with a full boat tail. But the you pick up a bunch of laminar drag. I don't think small kammbacks would help. Check out these Flow Illustrators on this very thing. (I thought they may help too, so I checked into it)

http://www.youtube.com/watch?v=EKX6NUZMUjY

http://www.youtube.com/watch?v=W6Z3L4-PGog

[sleeeper]

I got an error from youtube trying to view those. I actually ran my own flow illustrator simulations and "visualized" a noticeable shrinking of the eddies but have not uploaded anything to youtube. I used re=1000 and dt=0.03 and ran it for 30 seconds. It took about 10-15 seconds (at dt =0.03) for the eddies to shrink thought so I'm not sure such a short look would really capture it. I have noticed that the initial conditions when you start a video are not steady state and can take a little while to stabilize. I'm not sure why a kamback which is proven to be useful for the vertical component would become doomed in the horizontal. As for my other thought, in the case of full sized pickups especially 4x4's there is a significant amount airflow underneath the truck that it seems could be put to some use to increase the pressure in the center of the tailgate and shrink those eddies.

[sleeeper]

One more thought,

I couldn't view your video but the still image shown looks like you have added trip edges-I am talking about Kamback style where a short ~12" piece curves in from the corner and forms a abbreviated boat tail. Maybe you included that later in the video but that may explain the result?

[bondo]

This is maybe one solution to reduce the swirling eddies formed at the rear corners of a four wheeled vehicle as it passes through the air.

This concept ducts the air and then rudders the flow to maybe dissipate the eddies in size and thereby reduce low pressure areas. Just a concept.

Bondo