Aerodynamic Brick Thread: 1990 Vanagon Carat

[freebeard]

As we all know, fluid flow is not very intuitive.

Quoted for truth.

You could lower your part to the drip-rail and space it back to have an upward-facing opening. Then use a manumometer, or a homemade equivalent, to compare the pressure on the roof and on the backside.

My problem is that I have trouble getting other people to implement ideas I've had (I operate within constraints). Here is what I would do:

The problem with collapsible boat tails is rigidity and holding shape. This proposal is for a rigid, hinged diffuser hinged above it's lower surface so when it's deployed it reaches forward under the rear valance. No reason it couldn't be a plenum for cooling air into a Coanda nozzle. The superstructure could have inflated tubes or fiberglass rods to define the shape.

[dhehnke]

I like the idea of a collapsible tail as well, that would be cool to see in action. That is a good idea with the rigid hinged part.

As far as coanda nozzles and such, I need to do more research to say anything about that, but it sounds like a good addition.

[seifrob]

How are you going to test your ?wing? ( Inverted wing? Gniw?). It looks like ideal candidate to coast-down test, but with multiple runs (without the gniw, upper edge 2 inches above roofline, 1 inch, flush, without the gniw) Do you have access to some local airfield by any chance?

[dhehnke]

Unfortunately I don't have access to an airfield...

Initially just drive it for a bit. I often make the 2 hr drive from Portland to Eugene. It's pretty flat, and I could record my mpg for the trip there and back as compared to what I usually get.

I would like to hook up a manometer if I can figure out a good way, just to see the pressure difference between various spots. I also want to attach some streamers to various spots just to see what the flow is doing there...

[chefdave]

Sounds a good plan gives you a real world result.

[Xist]

People spend money on:
1. Things that work.
2. Things that look good.
3. Things that look like they work.

My Civic has a spoiler. I like it. Members on here have removed their spoilers or swapped trunk lids to get rid of their spoiler. Most spoilers fall in category 2 or 3.

[freebeard]

As far as coanda nozzles and such, I need to do more research to say anything about that, but it sounds like a good addition.

The Coanda effect is provable, used mostly in industry, and hasn't been applied to cars to my knowledge.

Do you see the 'stinger' that stores over the roof of the van? Imagine it was concave, with a [forward facing] baloney-cut upright pipe at it's focus. What that would do is add an energetic jet to the center of the wake. Hopefully shrinking it.

Theoretically, anyway. My panel van was half-way through a restoration when I let it go.

Of course, this could be reduced down to something no longer than those big rig 'trailer tails' (which only treat the top half of the wake so they can back up to loading dock).

Speaking theoretically again, a differential manumometer need be nothing more than a long piece of surgical tubing with a downward facing U-bend in the middle. A bubble of liquid in the bottom will be driven up one side or the other. For comparison, not absolute values.

[dhehnke]

I remember many years ago writing a paper for high school, using the coanda effect to describe how a wing produces lift. I hadn't thought about that word for a long time. I was super into model airplanes as a kid.

I have access to a calibrated manometer. I am just trying to picture how to rig it so I can actually read what it's saying and not disrupt the flow.

[freebeard]

A pitot tube points forward to measure static pressure to infer velocity.

Wind tunnel models use ports flush and normal to the surface, likely to not disrupt teh airflow.