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Old 10-05-2017, 12:05 AM   #1 (permalink)
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How does this work??

Watched a car drive over a sheet of newspaper today. The newspaper went under the front of the car, a bit to one side, and then shot out from the same side between the front and rear wheels.
So, that means higher pressure under the car than beside, right? How is this so? I always figured that faster moving air under the car created a low pressure area and sucked air in along the sides.
Any thoughts?

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Old 10-05-2017, 01:24 AM   #2 (permalink)
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With all of the turbulence between the messy undercarriage and the ground I imagine it is a high-pressure area.
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Old 10-05-2017, 08:57 PM   #3 (permalink)
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Cars are usually designed so cooling air exits from the wheel wells. Perhaps air was not able to exit fast enough and built up under the car, particularly if their air dam was damaged/missing.
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Old 10-05-2017, 11:42 PM   #4 (permalink)
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The lack of smoothness creates a lot of turbulence, which is generally higher pressure, but the particular phenomenon you witnessed was a result of the wheels, they (combined with the wheel wells) create a not-inconsiderable low pressure zone behind them and a small but intense high pressure zone in front of them. The end result is that the wheel would suck anything on the underside of the car towards this, but because inertia, the newspaper came out behind the wheel and was attracted to the *somewhat* more attached and lower pressure on the side of the car
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Old 10-06-2017, 12:29 AM   #5 (permalink)
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When I tuft tested my side skirts, I saw air going under the side of the car. But I have an airdam/splitter and grill block keeping air from going under in the front.
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Old 10-06-2017, 01:32 AM   #6 (permalink)
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That makes sense. I guess reducing that low pressure area behind the wheel would be beneficial to fe.
Thanks for the input.... glad to know I am not the only one who looks at this kind of thing!
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Old 10-06-2017, 01:33 AM   #7 (permalink)
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Those skirts are low. Is your dam/splitter at the same height? Belly pan?this is what I would have expected, and was surprised to see the newspaper shoot out the side.
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Old 10-06-2017, 02:24 AM   #8 (permalink)
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Those skirts are low. Is your dam/splitter at the same height? Belly pan?this is what I would have expected, and was surprised to see the newspaper shoot out the side.
The center of the dam/splitter is higher than the skirts, the flaps in front of the tires are lower. No belly pan.


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Old 10-06-2017, 01:49 PM   #9 (permalink)
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Thanks for posting. I can never find pictures of that, it's one of my favorite air dams.

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