I would agree that Georgi's bikes are anything but laminar flow bodies. Yet they are quite practical vehicles and can be ridden in 20+mph gusty conditions. I have two hanging on my wall (Varna 2, the grandfather of the diablo3 and a Mephisto clone (unfinished)) and have personally witnessed the Varna2 being ridden on a closed course in dust devils at 50+ mph for an endurance race.
Of course Georgi doesn't use any engineering or computers, just what looks good and experience. Georgi has told me that as long as the surface is not wavy then the finish doesn't make that much difference at the speeds that human powered vehicles run. I believe him. He goes out at night with a flashlight to refine the shape of his plugs using tangential lighting looking for waves.
Back to the subject.
Quote:
Originally Posted by aerohead
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At Battle Mountain I grilled the Cal Poly team( I think it was).They were using CFD for engineering their bike and believed that Cd 0.11 was probably the 'range' for bikes running,like Varna Diablo III.The day I was there,Sam went 81.6-MPH in it......
....For road vehicles above 20-mph,and for the surface roughness conditions obtainable in automotive finishes ( or even polished surfaces ) the given surface grain size versus vehicle length/velocity relationship mandates that the Reynolds number go 'critical' and boundary layer transition to ' turbulent' with a ground/air velocity of 20-mph.Which is all good for road vehicles,as the turbulent boundary layer allows the separation point to be moved rearward,allowing pressure regain and reduction of pressure drag,the largest component of profile drag....
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