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Old 04-12-2010, 07:20 PM   #56 (permalink)
aerohead
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Cd change

Quote:
Originally Posted by donee View Post
Hi Dave,

Yes, that is right. The oblique view from above gives a clear view of the swirling air flow at a seated head position.

As it is a model, they may not have matched the Reynold's number to that of of a full sized vehicle. But what is shown in the model wind flow seems to me to be similar to what the air pattern would be based on what I was hearing when I was in the new beetle.

Is this a case where the automotive speed range makes a big difference in the air flow? Is it the unique shape of the beetle that causes this? Does the Cd change with speed dramatically in the beetle?
For the size and velocities of automobiles,critical Reynolds number is achieved by about 20-mph,and from there,up to 250-mph,where compressibility effects begin to rear their ugly head,the drag coefficient is a constant along with air patterns.
Of course,that's all predicated on zero wind,or zero-yaw condition when wind exists.
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