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Originally Posted by sregord
I'm not finding a "Continuum Dynamics tail"..but "... aerodynamic backward's-facing step" is plentiful. These only show the step(off) surface & the reattachment zone surface being parallel... except the step in a wing.
Following your graciously provided instructions "measure 'down', 'over', and 'up',"..etc. It appears that the length down stream the step could be longer than the reattachment zone..based on the Mair tail, just not shorter? Is there any concern regarding the 3-4" radius of Moby's corners..of the step?
The Ame's wind tunnel at Moffett Field is familiar. I called NASA (1998) requested a tour, "for my son's high school science project". We didn't get into the biggest, but had a great day touring a smaller one. One of those sure would be handy.  |
Their research coverage may have been limited to Popular Science or one of the like periodicals. I'm sure I had images in my Photo Bucket account, but they were hijacked and I've lost the use of them.
As to step length, what we're trying to do is something Frederick Lanchester addressed in 1907. I published a link to his book, which illustrates a streamline body of revolution reduced to a very low-resolution bar-graph calculus.
Both the forebody and aft-body are presented as 'steps', of which the air makes its way across, even though reduced to 'chunks' of the original contour.
Think of the airship Hindenburg made up of tiny steps rather than a smooth ,continuous contour.
As long as the gross contour remains, you're still maintaining sectional density within enough resolution that, any pressure spike present, does not have enough adverse pressure gradient as to permanently 'trip' the boundary layer flow, with zero chance for reattachment.
NASA's tail, has an aggressive 'buttocks', and while it never slopes beyond 20-degrees, it's 'radical' compared to Mair.
Mair has a more subtle buttock, allowing a more gentle pressure rise, less adverse than NASA's.
Walter Korff, of Lockheed Aircraft Co., and designer of the Cd 0.1165 Summers Brothers' 409-mph' Goldenrod', has an even more gentle 10-wheel tractor-trailer van boat-tailing, Cd 0.20. It's reminiscent of the Fairchild C-119, 'Flying Boxcar' aft-body. That may be a 'lost' image as well.
Korff's tail uses the body width as the foundation for design. It would be a very 'safe' architecture, with high probability of success to a non-millionaire.
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The rear radii on Moby will separate at 5-'seconds' after 'noon' on their curvature, if you're observing from the 'sides', relative to flow. They've got to.
So you can just ignore them, and treat them basically as a 'straight' edge, if that eases fabrication and attachment, leaving all the actual streamlining to the new additions.
PS That's great that you guys got to see Palo Alto. It's on my bucket list.