View Single Post
Old 04-11-2022, 01:32 PM   #98 (permalink)
Master EcoModder
Phase's Avatar
Join Date: Mar 2022
Location: oregon
Posts: 913

Black Bullet - '19 Hyundai Ioniq Hybrid Blue
Thanks: 1
Thanked 466 Times in 379 Posts
Originally Posted by aerohead View Post

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.
definitely smoothing out under belly and adding rear wheel skirts. ive seen some people on the ioniq forum say they may not do much because you have to SLIGHTLY curve them outwards for wheel clearance and that that will add frontal area and will just offset the benefits. wouldnt covering the whole wheel well with a skirt offset the few inches of front area added by a lot? especially if id be maintaining attached airflow? personally i feel like the attached airflow is way stronger than adding a inch or two of front area sticking out. obviously ill test it, but what are your thoughts?

extending the sides for the box cavity boat tail will be the harder thing to do, versus just extending the top and bottom spoilers
  Reply With Quote
The Following User Says Thank You to Phase For This Useful Post:
aerohead (04-11-2022)