Quote:
Originally Posted by mikesheiman
Interesting, if I have it right, the key point here seems to be that pressure is -lower- in the sunroof area, for example, than behind the car, which reverses the desired air flow (doh!).
However, I'm wondering -why- this is true...
A guess (please feel free to correct)
*) The roof and windshield area do not curve smoothly/continuously into each other, causing the windshield to "throw" the air over the sunroof and create a low-pressure/turbulence area
Yes, I'm considering the idea of reshaping/custom-creating the front/roof joining area (technical term for this?) to prevent said "throw" if this is the case.
The speed lost in the actual duct due to it likely not being perfectly smooth does seem to be a definite issue.
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The reason it throws the air over the sunroof is purposeful, so that the occupants don't get blown around with the fast moving air coming into the sunroof. The low pressure above the sunroof is the design intent. Have you seen and wondered about the little flip up spoilers that pop up at the front of the opening when you open the sun roof? Additionally, throwing the air over the top helps lessen the drag, opposed to, if the air actually enters the cockpit area.
Every benefit has an opposing compromise.