Florence_NC
Senior Member
- Joined
- Sep 25, 2018
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- Location
- North Carolina
- Vehicle(s)
- 2018 Type R
And to add more, entrainment is a real effect, and it does have some existence in a vehicle at motion.Fair enough. I was thinking along the lines of introducing air entrainment
A couple of places I can think of on a car where entrainment would be highest would be a place like the hood vent you talked about. If you place a hood vent near the front of the hood (basically directly behind the radiator) where the air is passing over at a high velocity, some entrainment would occur. Also as mentioned before in this thread, a drivers window rolled down 2 inches, opening into the high velocity air passing outside of the window. This would also have some entrainment effect.
But in the case of the hood, the fast air over the top of the hood near the grill creates a low pressure due to Bernoulli, while the air passing through the grill is pressurizing the volume under the hood. This creates a big pressure differential. Same thing with the window down, the air passing on the outside of the window is fast, thus causing a Bernoulli-induced drop in pressure outside the glass. While at the same time the relatively still air inside the car has a higher pressure. And the cabin air pressure can be boosted even more by the cowl vent which feeds the heat/AC system and can pressurize the cabin. In both the hood vent and window-down examples, entrainment does move some air. But the pressure differentials are a much, much bigger source of air displacement.
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