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Old 08-01-2015, 07:29 PM   #34 (permalink)
PeterS
Master EcoModder
 
Join Date: Aug 2011
Location: East coast of Australia
Posts: 393

Yella Peril - '80 Mercedes 240D sedan
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Quote:
Originally Posted by aerohead View Post
*you're streamlining to reduce pressure drag.
*you must reduce or eliminate separation to do this.
*historically,gentle,progessive plan taper is the only way to accomplish this.
*and this requires a curvilinear pathway.
*a straight curve has too much pressure gain to respect a turbulent boundary layer's needs to mitigate counterflow,eddy initiation,then full-blown turbulence.
*to complicate things,the body upstream of the taper is mutilated due to the cavity for the rider,so the onset flow to the tail is adulterated already.
*boat-tailing requires clean,turbulence-free flow to perform properly.
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*Since your fairing is a crude,upright wing section it cannot tolerate a Kamm truncation.Chopping it off creates an exponential drag increase.
*for drag reduction the tail needs to be curved to a point,even if it's not to an ideal length.
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*if you're concerned about crosswind and gust dynamics,it's my opinion that you need to ride with extreme vigilance,and use the body cavity to lean out,using body English to address your immediate riding environment.

Here are some examples of proper streamlining
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Thank you but I am well aware of what ideal streamlining looks like , the problem is that it isn't practicable to use on a busy road . I'll end up dead .Lovely pictures though.

''*a straight curve has too much pressure gain to respect a turbulent boundary layer's needs to mitigate counterflow,eddy initiation,then full-blown turbulence.''

Could you explain that in other words ? I'm finding your meaning a little hard to derive .
I've modified my rough model , improving the nose area shape and smoothing it more back to the rider's position, the rear remains flat but tapered.

My understanding of this is that it is the angle at which the body leaves the air that is most important. I appreciate that my design will generate some flow separation forward .... but then that is the whole point if the side lift is to be avoided and that seems the primary gain, it could keep me alive.

Last edited by PeterS; 08-01-2015 at 08:05 PM..
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