Snow mods: We have been bested by mother nature.
 

It seems that high winds and snow, in the hands of mother nature crafts aerodynamic shrouds that put us to shame:

Snow Mods: Ten Cars Aerodynamically-Enhanced By Mother Nature - Snowpocalypse - Jalopnik

The snow was accumilated and erroded and the most aerodynamic shape found naturally. The result is impressive in the pictures, when I first saw it I thought it had been carved by cheeky ecomodders. So did anyone in that area get out and make a mould or template from those shapes? :D

Seeing those fantastic shapes makes me wonder...

Wouldn't it be interesting to have access to a computer program that would
simulate how wind driven snow builds up on a 3D object. This goes beyond
mere flow line visualization. And it goes beyond showing velocity and
pressure distributions in 3D.

For sure it would take a lot of computational power. And there would be the
matter of specifying how the snow would accumulate, "stick" together in
moving air.

I have come across references to snow drift prediction software used in
archetecture and mechanical science applications. So, maybe the capability
already exists in the halls of academe.

But I would think that a large part of snow drifts is the flakes sort of
"falling out of solution" as opposed to "sticking-to on the way by" :confused:

Several of those vehicles' "snow-aero" was influenced by other factors than the straight flow and existing vehicle shape...

While the photos are interesting, they're not scientifically viable at all.

However, wind deposition can show the most aerodynamic shape for a dense object over time. A long time, usually.

Also, without knowing the approximate wind speed when those shapes were produced, it's impossible to know whether or not the shapes would be ideal for a specific speed over another. Average wind speed creates differing deposition shapes, and is still affected by other factors, such as sheer direction and variable speed, as well as the presence of objects which might create resonance at a given speed, or compress flow between the object of resonance and the object of deposition, which would change the flow profile, and thus, the shape of the deposit.

Awesome pics and link, thanks. Send more !


Why there are unknown variables (some were influenced by the vehicle in front or behind) the results do agree with testing here and by Hucho.
Note the obvious Kamm effect on the cars. The minivan looks a heck of a lot like "AndrewJ"'s Civic doesn't it????
The places where the wind creates high pressure zones will errode the snow and low pressure zones will cause the wind to slow allowing the snow to stick.
This is a step up from "dirt testing" i guess :thumbup:


"Resonance" ???? What the heck, I thought resonance only occurred within a tract or body not open atmosphere. Are you suggesting they could be skewed by aeroelastic flutter?

Resonance may be the wrong word there.

The effect I meant to describe is the oscillation that occurs behind an object in it's wake. If that oscillation happened near a vehicle during the formation of the wind sculpture, it would have affected the actual airflow and deposit sites.

Just because the shape "looks" like it matches something you've seen on here and in Hucho/other books, doesn't make it ideal.

Come on Mother Nature! No wheel skirts?

I was kinda wondering the same. Here's one that has a 'flexible' skirt design.



http://farm3.static.flickr.com/2374/...904dc0784b.jpg

Here's my contribution...

I think the ZX2 (Blue Car) looks a bit like an Insight!

I liked it how the honda civic ended up looking like the new CRZ in side profile.

Snowmod:
http://cache-03.gawkerassets.com/ass...onda_civic.jpg
CRZ:
http://www.zcars.com.au/images/honda-crz-concept51.jpg

These kind of look like someone glued polystyrene foam all over the car then carved it into shape, which I wondered about doing some day, perhaps with a old clunker, just to see if it works.

There's another garage ecomodding technique someone could try. Lather release, Vaseline, on base/donor Honda coupe car. Cover with visqueen plastic. Boxed out with cardboard fences. Fill with foam blocks. Spray foam insulation to fill spaces & gaps to desired 'billet' form. Set. See snow CRZ sample. Fabricate 'hot wire' slicer & carve out desired form. Two-part putty finish, proper surface, prime & paint. For aero testing only.

I've built full-sized prototypes with foam. Very very... VERY messy!

I started leaving the snow on the roof of my Jeep to get an idea of what the flow did on top. Looks like the air re-attaches about 1/3 of the way back on the roof.

Here's a stratus I saw at school today... Looks a bit like a Lotus Esprit.

That stupid snow completely failed to fix the flow over the backlight :mad: I say we fire Mother Nature.

Give her a break, she ran out due to global warming. :rolleyes:

Try looking at the shapes that snow gets drifted into against other objects besides just on cars. And also take into account the liquid density of snow. Wet snow will pack and freeze and the shape we see may not be so much the result of aerodynamics as of imobility. While dry powder snow flows quite nicely and should leave some interesting ideas to test.

I did today some snow testing with powder snow and got pretty good results:

http://www.youtube.com/watch?v=ZFGaD...TfIAFA&index=2

http://www.youtube.com/watch?v=lG_J7...ature=youtu.be

Testing will continue tomorrow morning because it will propably as much next night, already 3 cm ;).

That's what he's saying, anywhere the snow stayed is a sign of poor air flow.

Wonder what you could use in a warmer climate, talcum powder, bull dust,
flour?

Oh wow, that's awesome! You can even see how door handles mess with your aero.

Yes if your car aero is perfect there would not have any snow left after test. I would be interesting to see for example aerocivic do the similar test. he has pretty good Cd but pretty rough surfaces. So the pockets should fill with snow.

Today snow was thickier and results not so good:

http://www.youtube.com/watch?v=8ETXy...ature=youtu.be

So you need powder snow. If you are able to make snow balloons it is way too thick.

snerodynamics
 

I know how much you guys love snerodynamics...

http://i146.photobucket.com/albums/r...ps9a544e17.jpg

http://i146.photobucket.com/albums/r...ps1c3a1090.jpg

snerodynamics

Frank you are full of it today :)

No wonder the Finns are such great ice racers!!!!

regards
Mech

Just today? :p

This is exactly why I asked in another thread about optimum nose shape.

Mother Nature tells us with her snowscapes that nose shapes count. It would be wonderful if somebody could extract coordinates for these shapes.

Also, for shape modification around windshield wipers, mirror stalks, door handles, etc., you could use Great Stuff expanding foam to pretty much duplicate the snow sculpture. Protect the car surfaces with Saran Wrap, slather on Great Stuff, and squeege and/or sand the foam to match the snow shape. Test.

If you build, say, a 1/4 scale model and had powder snow available, you could mount the model on a turntable with a weathervane tail, set it outside in a snowstorm, and study the results. The turntable/weathervane would keep the model facing into the wind.

BTW, in the pics above, the snow profile shape is quite similar to the leading edge of an airfoil, and also quite similar to Hucho's (page 158) "ideal" nose shape. I'd just like to see how such a nose would look in planform, i.e., from above.

Just keep in mind that those nose modifications are the optimal mods for those OE nose shapes, and the Kammbacks are the optimal what sticks and doesn't get blown away shapes for those bodies- not necessarily what's required to maintain attached airflow.

Beautiful shots, though.

Frank Lee -- Thanks for bumping the thread. The Jalopnik article and Vekke's video are informative.

I woke up yesterday morning to what would have been perfect snow. It came down so gently it drifted half-way back into the carport. Halfway on the roof of the car, not the floor.

Vekke, first of all, thanks very much for all the research and development that you do, and for sharing with the rest of us.

Questions: How far and fast to drive with snow on the car to get best shape? In other words, if you drive too far, all the snow will be blown off, with less than optimum shape. Drive too short a distance, and not enough snow will be blown off, with less than optimum shape. So, how far and fast is just right?

And, have you considered measuring depth and coordinates of the snow shapes? For example, the roof has the deepest snow about 1/3 back from the windshield, then tapers to the rear and sides. Perhaps a grid could be made, recording the snow depth at various coordinates. Laser scan?

Maybe when you come back from a drive, spray the snow with a mist of cold water, to form a solid crust on the shape. Then make impressions. From the impressions make foam copies of the snow shape, and glue on to your Lupo. (?)

planform
 

If you have Hucho's book,there should be plan views in the 'trailer' section,there should be one for Moller's VW microbus, VW's LT (Vanagon),and back in the commercial vehicle section for buses and 18-wheelers.
It's just a matter of leading edge radii along with side camber.
The caveat is the 'bulbous' (or 'Bug' as Koenig-Fachsenfeld referred to them) nose investigated by Hans G'o'tz,which has the all-around lowest drag when crosswind is factored in.
These date to 1911,with Oscar Bergman's airship car,which predated Count Marco Ricotti's Alfa Romeo 'trompe le vent.'
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"There is no magic radius.I think you have to stay away from an obvious hard edge,and then there is quite a bit of freedom as to how much you soften it,depending on what you want it to look like and how much you can curve it without interfering with mechanical components."
David Holls,Director,Advanced Design,General Motors Corp.,1982.
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"Once you've got a clean front end,well over half the problem is how you handle the rear of the car." Chuck Torner,Director,Advanced Engineering,General Motors Corp.,1982.
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" the shape of a body in front of the largest cross-section has only minor influence on the total drag.The main contributions for the drag force originate from the rear part of the body." Wolf Heinrich Hucho,Director,wind tunnel operations,Volkswagen AG

They agree on the rear, but [may] disagree on the front [, it's ambiguous].

My Escort wagon snow kammback:

http://i240.photobucket.com/albums/f...pswejxou6t.jpg

I was in Colorado last week and noticed that the snow that tires would kick up would stick to the bumper, fashioning some VERY flush ice-fairings.

ennored...it's a traveling "Sno-Cone" What flavor...Root Beer?

I know, not a very problematic area, aerodynamically... but I found the form aesthetically pleasing:

http://i146.photobucket.com/albums/r...ps8260fe4c.jpg

http://i146.photobucket.com/albums/r...pse41a79b8.jpg

optimum
 

the shape is similar to Hucho's ideal shape from 1976 or so

Driver side and passenger side pattern is different, apparently because of the presence/absence of the rear view mirror.

It is a problem area aerodynamically. The snow fixes it.

We accept the problem because you couldn't see through a windshield at that angle.

The cowl/bottom of windshield aren't a problem area.

https://ecomodder.com/forum/showthre...tml#post420535

Per Xist, I guess aerohead agrees. Ignore the initial caps, Xist doesn't respect handles.

Raising the hood is always good.