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Old 07-07-2022, 01:43 PM   #1 (permalink)
aerohead
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Dr. G. Furhmann's streamline bodies of revolution

If this link works out:
On page-14 and 15, you'll get a look at four different, identical fineness ratio, airship streamline bodies of revolution investigated numerically, and tested empirically, by Dr. Ludwig Prandtl's colleague, Dr. G. Furhmann, at the AVA G'o'ttingen, Germany, 1911-12.
Pressure profiles are shown as 'ideal inviscid' results of Bernoulli's Theorem, which contains D'Alembert's Paradox, against actual pressure measured on model airships in the AVA's wind tunnel.
You'll notice on page-14, that shape- II has the lowest total drag coefficient of the four shown. You'll notice that this form is similar to what Wolf Heinrich Hucho presented for the L/D= 2.5:1 streamline body of Cd 0.04, in his drag table, sourced from Sighard Hoerner's book, 'AERODYNAMIC DRAG.'
And you'll notice that shape-IV, with the 'pointed nose' has higher drag than shape-II.
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The other thing I'd emphasize is that, even when the viscous shearing effects of real flow are measured, that ALL four bodies exhibit POSITIVE pressure over their aft-bodies, which appear to fly in the face of conventional wisdom.
Mercedes' 1978 C-111 III ( long-tail ), with its 'blister on a body' greenhouse, aft-body recovers to 'zero' (neutral ) pressure over the final 1036mm of body length, whereas, a true half-body generates actual positive pressure in the same area.
The half-bodies also demonstrate the lowest negative pressure coefficients.
https://web.stanford.edu/~cantwell/A...mic_Theory.pdf

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