Quote:
Originally Posted by aerohead
The 2.5:1 value comes from DVL,Germany,1945.Above this fineness ratio skin friction works against any reduction in profile drag for a net loss.
The 3.33:1 value is very close to the minimum for 2-dimensional flow around a strut.
The difference between skin friction for a 3.33:1 may be a trade-off for stability as is certainly the case for airships.
The blue-fin tuna has the lowest drag coefficient of the pelagic fishes,it's frontal area occurs at aprox. 33 % of body length as of those of the lowest drag fusiform shark with 2/3rds boat tail.
I just enjoyed a preliminary drive in a half body-of-revolution fish-like body and am not convinced that we can't drive around in them.
With respect to the motorcycle,are they exempt from the laws of fluid mechanics?
And if there was any crosswind present,would the motorcycle not "miss" the wake of the pie-plate.
And if the MC were already in the wake of a truck,would the pie-plate not also be embedded within the turbulence of the truck,with no hope of performing while "submerged" in turbulence?
|
We'll just have to disagree on optimum fineness ratios. My 3.33:1 comments based on Zedan et al, Bruce Carmichael, Heinrich Hertel, and Dr. Hoerner's books, all in my library, based on tests of optimum fuselage pod shapes, etc., i.e., bodies of revolution, not air foils. Also measured proportions of shark, tuna, etc.. per Hertel. That's my story and I'm sticking to it.
Motorcycle pie plate efficacy depends on speed and crosswind gradient--the faster the less effect from a given crosswind. You knew that.
The pie plate on a stick trick might work pretty good on a motorcycle, since the basic essentially concave shape of an unfaired motorcycle is so bad to start with. Easy to test. Actually, those crude windscreens on unfaired Harleys reportedly help somewhat, and have
some of the aspect of pieplate on a stick, just not so far out in front. A serrated edge on the pieplate might also help--makes little vortices that may counter-rotate each other and dampen turbulence. At least, that's part of the theory of serrated trailing edges on new jet engine nacelles, said to be quieter than conventional.
We won't know until we try it. Can the motorcycle mod guy be talked into this? A simple coast-town test might tell the tale.