Quote:
Originally Posted by Otto
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.
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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