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Old 04-11-2022, 10:41 AM   #97 (permalink)
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IONIQ tail

1) If you'll look at 2:23 into the video, you'll see how the 'fully-boxed' tail elongation is capturing the smoke in the wake.
2) This is what you're after.
3) Flow @ top, sides, and bottom, is decelerating along the reducing cross-section of the 'tail', and recovering pressure the entire way.
4) When it separates from the new trailing edges, it's at lower velocity, higher pressure, according to the Bernoulli Theorem.
5) This increases base pressure.
6) Increased base pressure reduces pressure drag.
7) The reduced pressure drag is the 'streamlining.'
8) Upper and lower 'spoilers' might provide a drag reduction, however, nothing is going to compare to a box-cavity or boat-tail.
9) Technically, the sides must be included in the 'system.' Without them, you'll experience transverse pressure contamination.
10) And the tail will be useless without 'clean' onset flow. That means rear skirts, as much of a full belly pan as you can get away with, and a diffuser designed for low drag, not downforce.
11) The blueprint for the IONIQ doesn't indicate much boat-tailing in plan-view.
12) You need it, and the tail will have to respect whatever exists, then add to it, along a streamlined pathway, to provide for attached flow, the desired pressure recovery along the sides, and smaller wake, free of vortex-drag.
13) It's going to be a 'French-curve' environment, integrated into the OEM burst-edges.
14) The tail itself will be complex. The solution will be simple, not easy.
15) Solutions to drag reduction comparable to your target suggest a required 22-inches of elongation.
16) Since a receiver-mount cargo carrier is 24-inches, you may want to think in that direction, hence Basjoos' recommendation.
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Last edited by aerohead; 04-11-2022 at 11:11 AM.. Reason: add text
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