Quote:
Originally Posted by JulianEdgar
Figure 6.8, Hucho. I am seeing the stagnation pressure on the front face of the VW bus, and high pressure on the very slightly tilted windscreen. To suggest these forces are major forces offsetting lift is simply wrong - they are acting almost completely horizontally. Note how large the suction is as the airflow wraps around onto the roof, and subsequently, there is in fact no positive pressure anywhere along the whole rest of the vehicle!
Figure 2.4 Hucho we've already covered - as the caption says, it's a 2D schematic for a vehicle-shaped body in inviscid flow. That's not actually a real car in real air.
Basically, Aerohead's theories - or the way he applies them - are very frequently wrong, I am afraid.
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1) the topic was high pressure acting on the nose.
2) any vertical force component will be acting at the maximum distance ahead of the front axle. The 'aerodynamic lever arm' as Hucho describes.
3) a very light load acting on your outstretched hand/ arm, can easily overwhelm a very large load applied to your upper arm, close to your shoulder.
4) I gave you 4-examples, counterfactual to your thesis.
5) suction peak near the windshield header is separate topic.
6) pressure distribution downstream of the suction peak is a separate topic.
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* The streamlines for Figure 2.4 are exactly correct.
* The velocity profile based upon those streamlines will be exactly correct.
* The pressure distribution based upon the velocity profile will be exactly correct.
* And according to Dr. Dietrich Hummel's conditions, and your own metric, the pressure distribution in 'real' flow will be exactly correct for the first 85.5 % of body, and within 91% of depicted pressure for the last 14.5% of body length.
* It doesn't matter if the car is real or not. Mathematics of the numerical, 2-D model doesn't make a distinction between the two. That's the whole point of numerical models.
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*They're not my theories. It's fluid mechanics. If you'd actually studied Dr. Hummel's chapter on fluid mechanics, or anyone elses, you'd already understand.
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