The Kamm research cars

[JulianEdgar]

Originally Posted by aerohead

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3) You reported that, Dr. Thomas Wolf reported that, the 911 spoiler affected ' a stronger negative pressure gradient.'

I reported that Dr Wolf was in agreement with the description in my book on how the rear spoiler of the Porsche works. Attached flow without a spoiler, then with the spoiler, a stronger negative pressure gradient (higher pressure in other words) that causes flow separation where previously there was none.

You've disagreed repeatedly with that description, one which Dr Wolf specifically endorsed.

Aero of Road Vehicles 5th Ed would probably cause me to add a bit more to that description, were I writing it now.

[JulianEdgar]

Originally Posted by orange4boy

I have made no claims here of expert knowledge of aerodynamics but I sure know an ad hominem when I see one.

No, you haven't got that right either.

ad hominem: an argument directed against a person rather than the position they are maintaining

My argument is always with Aerohead's position - ie what he states here. As I have said, a great deal of what he writes about car aerodynamics is simply wrong, is outdated, or is misleading.

Each is a criticism of his position.

[aerohead]

Originally Posted by JulianEdgar

I reported that Dr Wolf was in agreement with the description in my book on how the rear spoiler of the Porsche works. Attached flow without a spoiler, then with the spoiler, a stronger negative pressure gradient (higher pressure in other words) that causes flow separation where previously there was none.

You've disagreed repeatedly with that description, one which Dr Wolf specifically endorsed.

Aero of Road Vehicles 5th Ed would probably cause me to add a bit more to that description, were I writing it now.

The sticking point for me is, the use of the term 'attached flow' to describe the original flow condition on the 911's rear contour.
Whatever transpired between the two of you is none of my business, but if Dr. Wolf actually agreed to the use of 'attached flow', as proper nomenclature, then I cannot abide by that.
' Downwash' yes, 'attached flow' no.

[JulianEdgar]

Originally Posted by aerohead

The sticking point for me is, the use of the term 'attached flow' to describe the original flow condition on the 911's rear contour.
Whatever transpired between the two of you is none of my business, but if Dr. Wolf actually agreed to the use of 'attached flow', as proper nomenclature, then I cannot abide by that.
' Downwash' yes, 'attached flow' no.

Well, you're on your own.

I have already said how the head of Jaguar aero described flow attached through the action of downwash as 'attached flow', and today I noticed that the Aerodynamics of Road Vehicles (5th edition P 37) does the same. In describing the tuft pattern on the Adler (1930s?) the book says:

On both sides the vortices roll up, pull down the flow coming over the roof, and keep it attached until the lower end of the slant.

So you can either be big enough to admit your mistake and correct it, or you can do as you have always done in the past and just say that you're right and everyone else is wrong.

[freebeard]

Potato-potatoe.

[JulianEdgar]

Originally Posted by freebeard

Potato-potatoe.

No. It's not just semantic, because if the flow is attached, it has quite different implications compared with if it just looks attached but isn't really.

[freebeard]

Air at the surface is motionless, held in place by atmospheric pressure. Air an infinitesimal distance away has a resultant vector that starts out normal and varies toward tangential, becoming tangential at the extreme. The 'magic' happens in between, minute excursions above and below barometric pressure.

Turbulent vortexes generate hot air that bouys the website statistics upward.

[AeroMcAeroFace]

Originally Posted by JulianEdgar

Well, you're on your own.

None of the aerodynamics books or papers I have ever seen have ever distinguished between downwash and attached flow, considering Dr. Wolf also agrees it seems like we are awaiting for some quotes or references clarifying where this confusion comes from.

Because at the moment it appears that the only person who differentiates between the two is aerohead. So I do agree with Julian here, you are on your own and I have seen no reference, quote or evidence to support your distinction between the flows.

[Vman455]

Originally Posted by freebeard

Air at the surface is motionless, held in place by atmospheric pressure. Air an infinitesimal distance away has a resultant vector that starts out normal and varies toward tangential, becoming tangential at the extreme.

I don't think this is correct; all the fluid dynamics texts I've read attribute the "no-slip" condition to intermolecular forces between the body and fluid, not atmospheric pressure.

When a fluid flow is bounded by a solid surface, molecular interactions cause the fluid in contact with the surface to seek momentum and energy equilibrium with that surface.

(White, Frank M. Fluid Mechanics, 8th ed. [Chennai: McGraw Hill Education, 2017], 32).

[freebeard]

Thanks. Liquids either wet their container (water) or don't (Mercury). I wonder if something similar applies to gases.