Quote:
Originally Posted by JulianEdgar
Happy to talk about the Insight, even though it's a typical red herring to the argument.
1. The Insight has a sharper downwards rear angle than The Template, and so according to Aerohead, it should have separated flow across the hatch.
2. Of course it doesn't - The Template cannot be used to predict separated / attached flow.
3. According to Aerohead, rear spoilers 'reach up' to separated flow. Of course, that applies only in very old cars with separated flow on the back, not a modern shaped car like the Insight.
4. So, according to Aerohead's theories, the spoiler on the back of the Insight cannot work - its rear edge is no higher than the standard rear lip.
5. But of course, it does work - it's operating in attached flow. (Just as with the recent, properly measured, data on the Prius and its trialled rear lip*.) It works by changing attached flow direction, not creating flow attachment.
6. If I'd followed the theories of Aerohead and The Template, the spoiler would look nothing like it does. A spoiler made to his theory of reaching up would also have increased drag with its larger wake.
You're quite wrong. I am - in your words - 'trashing' incorrect theories and misleading advice.
Would you rather people were continually led astray?
* testing that of course Aerohead immediately denigrated.
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1) according to Hucho the flow over the aft-body is technically compromised.
2) the 'template' can be used as a Go NoGo for attached flow.
3) in virtually every case for the non-high-performance car spoilers depicted in Hucho's 2nd-Edition, they were located in a region of separated flow. The 1st-gen Insight is compromised, for the reasons explained by Hucho.
4) the rear spoiler you've put on the Insight functions for the exact reasons as spelled out by Hucho.
5) I believe that your 'attached flow' nomenclature is amiss. There's an extremely high probability that you've mistaken 'downwash' for 'attached flow.' And for the exact reasons Hucho spells out. The sub-template Prius measured in Don Sherman's DRAG QUEENS had higher rear lift than the on-template LEAF. The sub-template, Mercedes-Benz notchback CLA 250 had the highest rear lift of the five cars measured.
6) a larger wake is of no greater drag if its base pressure is higher. For exactly the reasons as explained by Hucho. And until you master boundary layer theory, there's no way you'll ever understand the underlying premise for the template, and how it can be the canary in the coal mine of separation. Again, for the very reasons Hucho gave it to us. You may never get it. As mentioned by others, we throw buckets full of dots your way, and you remain incapable of connecting any of them. It's like terminal perspicacity - deficit disorder.
Please get a hold of Hucho and ask him about Hermann Schlicting's body of work.