Visual quiz

[aerohead]

Originally Posted by JulianEdgar

The normal mix of correct theory, incorrect theory, irrelevancies, very clearly no experience of on-road testing of a shape anything like this, extrapolated even weirder theory - and so on.

For people who actually want to learn, just look at the pressure chart and the flow pattern, and draw some obvious conclusions about the relationships.






And as for the rear spoiler, just mentally place one at the back of the car (say, the same angle as the windscreen but only 1/5th as high) and then look at what the windscreen did to the pressure of the attached flow in front of it.

I've provided a checklisted, item by item evolution of the phenomena, according to the science. Where one takes it is up to the individual.
Road testing isn't necessary. The photograph provides all the necessary information to make the verdict.
A look at the VW XL1 undergoing smoke flow testing will provide a look at what attached flow actually appears like.

[Vman455]

Originally Posted by aerohead

I've provided a checklisted, item by item evolution of the phenomena, according to the science. Where one takes it is up to the individual.
Road testing isn't necessary. The photograph provides all the necessary information to make the verdict.

Road testing; who needs it? And fuel economy testing; better to just believe that something works. Why test mods at all? Faith is all you need apparently.

The big thing on Priuschat these days is a VVT solenoid called the "Red Bullet." Many users have installed one on their cars and made ridiculous claims, such as one person who insists that it improved his fuel economy by 15 mpg. Yet no one who has installed one can explain what it does, not even the person selling them; they can't even be bothered to look up the (Toyota-available and published online) solenoid schematic and apply a little thought, let alone do a controlled test.

Originally Posted by aerohead

A look at the VW XL1 undergoing smoke flow testing will provide a look at what attached flow actually appears like.

Oh, you mean like this?



Hey, wait a minute! That shows flow detachment just like the Porsche! It's almost as if the flow over most of the car is turbulent and the streamlines are subject to random high-frequency fluctuation that isn't captured by a single still photograph. No, that couldn't be....

[Piotrsko]

My lessons in wing design (OMG not relevant here) says we don't really care if flow is laminar, attached, turbulent, whatever, as long as further following flows are low drag. Built many aircraft using wings that were thought to be using one of the above categories and !suprise! They all flew decent.

[freebeard]

flow is laminar, attached, turbulent, whatever.... !suprise! They all flew decent.

Even the whatevers?

[Piotrsko]

Particularly the whatever's.

Naca 0012 series operations in the reynolds transition portion flew generally the best. Since this is model scale applications, we don't know exactly what the boundary layer state is as it is immeasurable, therefore whatever

[freebeard]

https://en.wikipedia.org/wiki/God_of_the_gaps

[aerohead]

Originally Posted by Vman455

Road testing; who needs it? And fuel economy testing; better to just believe that something works. Why test mods at all? Faith is all you need apparently.

The big thing on Priuschat these days is a VVT solenoid called the "Red Bullet." Many users have installed one on their cars and made ridiculous claims, such as one person who insists that it improved his fuel economy by 15 mpg. Yet no one who has installed one can explain what it does, not even the person selling them; they can't even be bothered to look up the (Toyota-available and published online) solenoid schematic and apply a little thought, let alone do a controlled test.



Oh, you mean like this?



Hey, wait a minute! That shows flow detachment just like the Porsche! It's almost as if the flow over most of the car is turbulent and the streamlines are subject to random high-frequency fluctuation that isn't captured by a single still photograph. No, that couldn't be....

That photo was likely taken at an airspeed below 20-mph. It would be at sub-critical Reynolds number. You should have recognized it immediately. Not germane.
There's another image produced at supercritical Rn, necessary for the development of a proper turbulent boundary layer.
Is this just an innocent undersight or deliberate obfuscation? Conformation bias?

[aerohead]

Originally Posted by Piotrsko

Particularly the whatever's.

Naca 0012 series operations in the reynolds transition portion flew generally the best. Since this is model scale applications, we don't know exactly what the boundary layer state is as it is immeasurable, therefore whatever

Yeah, they test at three different Reynolds number, and without knowing that specifically, even though we know the wing dimensions, and turbulence factor, we can't peg the velocity necessary for that Rn to consider LBL or TBL or transition points.

[freebeard]

There's another image produced at supercritical Rn, necessary for the development of a proper turbulent boundary layer.

So where might we find it?

[Vman455]

Originally Posted by aerohead

That photo was likely taken at an airspeed below 20-mph. It would be at sub-critical Reynolds number. You should have recognized it immediately. Not germane.
There's another image produced at supercritical Rn, necessary for the development of a proper turbulent boundary layer.
Is this just an innocent undersight or deliberate obfuscation? Conformation bias?

Confirmation bias? I took a screenshot from the same video that produced the image you're talking about, just a few seconds after. Yeah, I'm trying to lead people astray....