Quote:
Originally Posted by skyking
Phil, if you see this I had some questions.
based on hutcho's diffuser graph, he talked about a maximum dimension for the total rise of the diffuser.
The trailer's problem is overhang aft of the axle, and dragging arse in certain driveway situations.
Proposed trailer diffuser is over 8' of length and needs to rise at least 7" to help with clearance. This is where TANSTAFFL kicks in.
1) 7" or more is a lot of air.
2) It has to come from somewhere. I see it filling in from the sides, and making a nasty double vortex bucket to drag around. Correct me if I am wrong.
I can make a moving diffuser with casters on it, that can "take care of itself" in those awkward situations. Would I make aero money if I reduced that rise, that angle?
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*Hucho shows a drag reduction for diffusers with up-slopes as steep as 11-degrees.The lowest drag is with 2.8-4-degrees,depending on where the slope begins underneath.
I don't have a calculator with me so it'll be tomorrow before I can check the slope.tan 2.8,or tan 4,times 8 would give you the desired rise in feet (if my brain's working).
*Square edges will induce vorticity according to Scot Funderburk's and Professor Carver's research at Texas Tech.You'd want something like this
