[JulianEdgar]

Originally Posted by aerohead

So let's consider 'flow-wrapping'.
1) lift is a function of pressure distribution.
2) pressure distribution is a function of velocity
3) velocity is a function of streamlines
4) streamlines are a function of body shape

Yes, all correct.

-------------------------------------------------------------------------------------
* the lowest pressure on the upper body of a contemporary automobile is at the suction peak, just ahead of the windshield header. The streamlines are closest together, the air is at maximum velocity, and pressure at it's minimum.

Incorrect. This is the case only if the curve at the top of the header rail is the sharpest having attached flow. On the old cars you like to quote - probably yes. On modern shapes, often no.

* if the body cross-section contracts rearwards of the roof apex, then by default, as the flow travels further aft, it gets slower, and its static pressure increases.
* the further the flow gets away from the suction peak, the slower, and higher pressure it becomes.

Correct.

-------------------------------------------------------------------------------------
A) if the flow can remain attached all the way to the rear, it will be at it's highest pressure, compared to the forward stagnation point, dependent upon aft-body length ( 'Verjungungsverhaltnis' as per 'Kamm's' research )

Correct.

B) adding a spoiler would only force the flow into a faster, lower pressure regime. A spoiler's deflection, or wing's negative lift 'will ' develop downforce, but at a drag penalty.

Incorrect with regard to a spoiler. Spoilers can decrease drag and lift. If you don't believe me, take it up with Dr Wolf, head of Porsche aero. I can dig out the direct quote from him if you want.

Correct with regard to a wing.

--------------------------------------------------------------------------------------
* 'Downwash' does not qualify technically as 'attached' flow. Downwash is an artifact of separation-induced attached longitudinal vortices, which generate the highest drag. The small wake, which is also an artifact of flow separation is not the same as a small wake generated from a progressively diminishing body cross-section which produces only a moderate pressure increase, incapable of triggering separation of the boundary layer.

Incorrect. Attached flow is attached flow, and separated flow is separated flow. You have changed the definition of attached flow to suit yourself.

-------------------------------------------------------------------------------------
* modern notchbacks demonstrate architectures that are all over the map. There are Hyundai Accents, Kia Rios, Nissan Sentras, and the like which don't improve on some notchbacks of 1986.
* Hucho addressed in 1986 all the caveats of windshield- to- roof transition, roof camber, aft-body length percentage, onset flow off the roof, boot height, and especially C-Pillar shape, which would govern notchback performance.
-------------------------------------------------------------------------------------

Incorrect. Hucho does not address car shapes of the 2000s, especially notchbacks. None of his notchbacks look like today's cars.

1) I could not find a single instance in Hucho's 2nd-Edition where a spoiler wasn't in separated flow.

Page 173, 272 of 2nd edition. The 5th edition has an extensive section on rear spoilers, including showing via streamlines those in attached flow (page 311). Your understanding of how rear spoilers work on cars of the last 30 years is completely wrong.

2) In his section on high-performance sports cars he recommended zero lift, or if you were going to introduce negative lift, then provide rear bias.

Correct

3) Schenkel's rear spoiler introduced front lift where none had existed.
4) beyond 17.8 mm height, Schenkel's spoiler increased drag, at the expense of downforce.

This refers to really old shape cars, no?

------------------------------------------------------------------------------------
Longitudinal centerline pressures on the upper body of a vehicle are meaningless without the underbody pressure profile, especially if there's an active diffuser.
--------------------------------------------------------------------------------------

Partly correct, but overstated. They're not 'meaningless', they're just not the full story.

Any information derived from tuft testing is extremely problematic. They clearly misrepresent the flow on the Beetle, New Beetle, and 911.

When real world tuft tests don't match your theories, I bet you find them 'extremely problematic'!