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Old 11-24-2013, 02:02 AM   #31 (permalink)
Otto
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Quote:
Originally Posted by Recumpence View Post
No worries. I am fine with people posting whatever they want.

Oh, I have to address the comment made on the last page about fog light position and air acceleration at that point. That was my assumption too. That was one point of my questions earlier in this thread that the fog lights and lower grille are in that area and both are there contributing to the turbulence of each other.

Matt
Bingo.

Bugger the accelerating airflow and you have half angles of turbulence of about 15 degrees all the way back from there, like a boat wake. You want a nice smooth and orderly acceleration of the airlow. In a sailplane, you may get laminar flow most of the way back on the canopy, then turbulent but still attached flow well aft of that. On a road vehicle, pretty much forget laminar flow, but keeping the turbulence as low and attached as possible would be most helpful, so a smooth and well faired nose is key. OTOH, if your nose is shaped like a bulldozer, it might not make much difference how good the shape is further downstream.

Down low where the foglights go is naturally draggy, since much of the stagnant nose air can't flow downward due to the ground, it has to mostly go laterally around the sides or up and over the hood. Then, there's gross buggery due to the effective yaw angle of the spinning wheels/tires, which really screw things up. So, the foglight region gets more air, accelerating even faster due to the concentration, and irregularities or bumps there are even draggier than they otherwise might be. Also, lots of crud accumulates, as well as rock chip damage.

You've done well go fair the foglights, and please report results as able.

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