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Originally Posted by shovel
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So - any other thoughts on this?
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I think your hypothesis is a good one, and the numbers you picked make sense to me as well, as a starting point. I believe you could coil the duct to make it more manageable?
I wonder if vehicles would usually benefit most from dual Helmholtz resonators, top and bottom. Really you need to consider the 3d shape of the turbulence, and which zones are out of phase with one another. Someone with CFD should take a swag at this.
The thing that really strikes me is that whereas boattails may offer increased interior volume, a helmholz resonator would reduce interior volume, so for many applications (my applications
) this would seem to be the less optimal solution.
I do think this aspect makes it unlikely to get used by auto manufacturers. This is for the after-market.
I see a lot of sense in one of your suggestions, a hitch-mounted resonator for large bluff-tailed vehicles - vans and SUVs, maybe hatchbacks and wagons. 30 cuft would fit there nicely, and yet not be nearly so large and obstructive (and odd-looking?) as a boattail, nor have stiff structural requirements and be easier to fabricate. Another interesting benefit, if we ever see motion-sensor-guided road-trains, is that the wake would passively return to existence if a following vehicle entered the tight draft zone.
Good thinking.
