Quote:
Originally Posted by aerohead
Neil,here are some highlights of wheel drag from 2nd Ed.:
*Wheels and wheelhouses essentially double the drag of a low-drag car.(VW's long-tail 'flow' body goes from Cd 0.0915,to Cd 0.14 when wheels are added)
*The closer the wheelhouse volume is to the volume of the wheel the lower the drag.
*The drag coefficient of the wheel does not vary as it is submerged within the bodies wheel well,only a drag reduction due to lower frontal area is actively involved.
*Open wheels,such as with Rumpler's Tropfenwagen,can double the drag (from Cd 0.14,to Cd 0.28,as per Wolfgang Klemperer's measurements of the Tropfenwagen at the Zeppelin Werke).
*Rear skirts cut drag if flow is already attached upstream.
*Front skirts,as,Adler-Jaray,Probe-IV,and AeroCivic can cut drag (9% with respect to Ford's Probe-IV).
*Just moving the wheels out flush with the body sides can mean up to a 16% drag reduction.
*Drag coefficients approaching those of basic bodies of Cd 0.07-0.09 can only be achieved through integration of the wheels into the body (2013 Cambridge University CUER eco racer is a current example,@ Cd 0.11,also NUNA series,and PACCAR.)
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Thank you Phil - I specifically remember the illustration of the air flow within the wheel well in the 2nd edition, and I looked for it in the 4th - as far as I could see, it is not in the 4th edition.
The 2nd bullet point is the one that stuck with me. Keeping the wheel well tight to the spinning wheel is the main takeaway.