Area-51
Joined: 03 May 2021
Posts: 391
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 Posted: Thu May 25, 2023 6:39 pm Post subject: The Obsidian Files - A Telling Tail |
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In this episode of the obsidian files we take a look at the empennage section of the europa and investigate ways to make it more efficient.
For this round of back yard science we have taken our pig and removed all of its apendagé but for the vertical stab... and vwalla our pig has instantly been transformed into a pug, sorry plug....
First we ran the pig (3B) head on into a 400kt stream of zero Alpha air and recorded the numbers... then we did the same with two variants, one with an added concave style empennage (Tubby Tub) and one with a more convex style empennage (3X2). The modelling on both variants was quick and crude with the sole requirement being directional signalling; better, or worse... what we ended up with was one shape similar to a Bonanza and the other a Pipistrel
Between all variants the results were not that dissimilar; so the compare & contrast aspect of this study was not remarkable.
Additional runs were also performed at 100kt.
Our meshing resolution was set to high and run through 100 solution cycles each.
Results were as follows:
Velocity 204m/s (400kt) Alpha 0 (Drag, Lift)
3B (factory) - 141kg, 2kg
TubbyTub (concave) - 149kg, 2kg
3X2 (convex) - 149kg, 11kg
At 51m/s (100kt) all pugs presented similarly at 9kg Drag and 0kg Lift.
Acoustically similar results were returned however the acoustic footprints were quite different and all becoming active aft of the fuselage max cross-section. A further journey into this phenomenon revealed boundary layer friction/cavitation as the cause for acoustic noise around the fuselage; slower air close to the surface being pulled back into free stream velocity some one inch above. As we increase velocity this acoustic noise increases in amplitude. However at 100kt this accoustic energy is only 50-60db; so we could say daytime ambient silent, i.e inaudible over the drone of nature.
So in the end the results were not greatly different to each other however out of the three little pigs the Europa's factory empennage shape came out on top on all accounts.
And a final bit of anecdotal assumption from these tests indicate 400kt Vmax with a 912 rotax at 20L/hr fuel burn is quite possible in a Europa providing the wings and horizontal stab are removed first...
This concludes this episode of the Obsidian Files and the subject open to discussion.
Europa declared "winner" again!
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| Factory - Acoustic - 100kt |
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| Factory - Acoustic - 100kt |
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| TubbyTub - Acoustic - 400kt |
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| TubbyTub - Acoustic - 400kt |
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| Factory - Acoustic - 400kt |
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| Boundary Layer Velocity - 400kt - Cross Section |
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