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Old Sep 09, 2012, 12:20 PM
reinking is offline
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A supersonic biplane....


A Supersonic Biplane that Whispers Where the Concorde Yelled

<http://www.txchnologist.com/2012/a-supersonic-biplane-that-whispers-where-the-concorde-yelled>

A .pdf file, "Adjoint based aerodynamic optimization of supersonic
biplane airfoils" is available here:
<http://aero-comlab.stanford.edu/Papers/AIAA-2011-1248-354.pdf>
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Old Sep 11, 2012, 03:44 AM
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Someone needs to brush up on their biplane efficiency research.

Biplanes generate big amounts of drag when the wings are much less than one chord separated. And this one certainly qualifies on that front.

The shockwaves when supersonic MAY work with the biplane wings to lower the shock wave reaching the ground but I'm not sure with all the interference drag between the wings that it could carry big enough engines to reach the transonic speeds where the shockwaves could come into play.

Anyhow if it has promise I'm sure we'll see it at least get some research time.
Old Sep 11, 2012, 08:34 AM
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Quote:
Originally Posted by BMatthews View Post
Someone needs to brush up on their biplane efficiency research.

Biplanes generate big amounts of drag when the wings are much less than one chord separated. And this one certainly qualifies on that front.

The shockwaves when supersonic MAY work with the biplane wings to lower the shock wave reaching the ground but I'm not sure with all the interference drag between the wings that it could carry big enough engines to reach the transonic speeds where the shockwaves could come into play.

Anyhow if it has promise I'm sure we'll see it at least get some research time.
You're thinking of subsonic. Things are quite different in supersonic. They are using shock interactions to reduce wave drag.

Quote:
Busemann’s insight was that the supersonic shock wave coming off of one wing could cancel out that produced by another, Hu says. Simply stated, his biplane configuration consists of a pair of airfoils with flattened triangular cross-sections. Busemann positioned the wings so that the vertices of the angled surfaces of each airfoil pointed toward each other—one oriented upward, the other downwards—with the flat sides at the very top and bottom. The center vertices create the expansion (low-pressure) wave that occurs between the compression shock waves at the leading and trailing edges of the wings.

In Busemann’s biplane, the high-pressure shock waves are created internally and reflect symmetrically between the two wings. This process “fills” the expansion waves coming off of the vertices with pressurized air, leaving no external shock waves to propagate out to the surrounding environment.
Although the above quoted is apparently old news. The newer research used an optimization-based approach to reduce the transonic drag that limited the original Busemann design.
Old Sep 11, 2012, 04:33 PM
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I still have my doubts about how well it'll perform during the run up from standing on the tarmac to transonic speeds where the shockwaves begin to take effect and alter how the air behaves.
Old Sep 11, 2012, 04:38 PM
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Bruce, from first glance it looks like off-design Mach numbers was a major consideration of theirs.


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