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Old 07-27-2019, 05:30 PM   #22 (permalink)
aerohead
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cancelling

Quote:
Originally Posted by hat_man View Post
I wasn't so much thinking it would generate "thrust". I guess I was seeing X amount of pressure applied to each side of a watermelon seed at the widest part somewhat cancelling each other out (180 degrees apart resulting in a 0). But the same X amount of pressure applied to each side of the tapered part being more than 0 because the side pressures being less than 180 degrees apart. Not that it would result in more than X, but rather a greater percentage of X being "usable". Does that make sense?

I can see the concept in my mind but just can't put it into words. Especially in tech speak.
You're describing the D'Alembert paradox,from long ago,before boundary layer theory was known.D'Alembert figured that there'd be as much pressure at the rearward stagnation point as at the frontal stagnation point.
Due to entropy, derived by kinetic energy converted to heat via viscosity and surface friction drag,it's impossible for there to be as much energy at the back of the body ,as at the front.
We're stuck with losing perhaps 12% of overall energy to skin friction.The good news is,that we can reduce pressure drag by basically 88%.Unless we're driving on the Moon,we're stuck with the 12% loss.
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