Rear kammback spoiler

[JulianEdgar]

Originally Posted by MHR1294

I think I got that right, it was in the mirror. If I still had the car I'd love to go and test it.

The droplets would run down from the upper middle of the screen, and spread towards the lower outer edges. So whatever direction that is!

The spoiler did angle down too, I'm sure I've got a picture of it somewhere I'll go have a dig.

That's pretty typical of trailing vortex direction - 99 per cent of cars develop lift. However, it's pretty rare to be able to see it so clearly in the rear vision mirror.

I had a look for some pics of the spoiler but wasn't sure precisely which one it was, so I'd be interested.

[MHR1294]

Best images I can find, it's not easy to see it's shape in Yellow

[Fat Charlie]

Ideals notwithstanding, given the preexisting condition of having an 09 Fiesta, the best way to find out is to try.

[JulianEdgar]

Originally Posted by Fat Charlie

Ideals notwithstanding, given the preexisting condition of having an 09 Fiesta, the best way to find out is to try.

Absolutely. An hour of testing beats a week of forum discussion, every time.

[JulianEdgar]

Originally Posted by MHR1294

Best images I can find, it's not easy to see it's shape in Yellow

Thanks for that.

My guess - and that's all it is - was that the slots were for changing flow patterns to reduce dirt deposition, as you have said.

It's not often mentioned in discussion groups, but there is a lot of professional aerodynamic tech literature on 'soiling' - how dirt covers cars. In fact I was reading something the other day that implied the air curtains on trucks are largely for this - to keep the doors clean so signwriting isn't obscured. Looking at the trucks I've seen since, the air curtains do all seem to be aimed at the doors...

[aerohead]

I am university trained in both aerodynamic and hydrodynamic measurement.My senior project (thesis) involved the aerodynamic streamlining of my VW Transporter,which yielded an increase in highway fuel economy,from 27-mpg,to 35-mpg.For nearly 6-years,I earned my daily bread making these measurements.I orchestrated the wind tunnel testing of the Cd 0.11 Becker-Lyon,BMW,LSR motorcycle streamliner.I hold two USFRA speed records.Since 1986,I've probably been part of only a rarified community of motorists incorporating a relative-wind-seeking,slewing pitot-tube/airspeed indicator.
Since my projects mimic vehicles which have already been analyzed by simultaneous recordings of 42-pressure tap/manometer readings,drilling my car full of holes,and bankrupting myself purchasing hardware would be folly.I've been happy enough to spend thousands of $ on 3rd-party testing.
In 1951, Sighard Hoerner reported that the average passenger car had a frontal-area-based coefficient of lift of 0.40.At 50-mph,this translated to 60-pounds lift,on a car of 4,500-pounds.
The 1935 Jaray-Adler Sportwagen was measured at Cl= 0.20,which would generate 30-pounds lift under the same conditions.
Spirit of Ecomodder indicated a Cl= 0.00591.At 135-mph she generated 8-pounds of downforce.For a 4,220-pound vehicle this is essentially a 'zero-lift' vehicle. Modelled in part,after the FKFS K-cars,which FKFS reported as 'neutral',as far as lift is concerned.
There's a reason Hucho wasn't concerned with passenger car lift,as of 1987.Can you imagine why? And can you tell the audience what has changed about Earth's atmosphere,or physics since then,that we should obsess over it now?

[aerohead]

On page 22,Fig.1.12.,of Hermann Schlicting's 'Boundary-Layer Theory',you'll find a complete pressure profile of a streamline body,presented originally by Fuhrmann.
You'll notice the positive static pressure acting on both the nose and tail,allowing for zero lift.
On page 23,Fig.1.14. you'll find a complete pressure profile of a Zhukovskii wing section,demonstrating a zero-lift condition (just as the 118-families of wing sections listed in Theory of Wing Sections) ,after the research of A. Betz.
If 'the exception proves the rule',then,when you make statements about the existence of lift for wings and streamline bodies,you'll want to include all the qualifying caveats/conditions.

[aerohead]

Originally Posted by JulianEdgar

Self-created authority? I am just a humble amateur working at home - never said anything else.



But my statements about lift are supported by the actual measurements that can be made on real cars. Your statements are not.




Richard Barnard is a world-renowned aerodynamicist. He started his career as an undergraduate aeronautical engineering apprentice at Handley Page Ltd, and later became Principal Lecturer and Postgraduate Research Tutor at the University of Hertfordshire, and is currently a Visiting Research Fellow. He is also a founder member of the UK Wind Engineering Society, and a Fellow of the Royal Aeronautical Society (FRAeS). He has been a consultant for numerous companies, including Jaguar and Rolls-Royce Bentley. Richard is the author of Road Vehicle Aerodynamics and has written many technical papers.

Um, I think I would back Dick's understanding of aerodynamics over yours....



Oh yes? Refer to Page 195 of my book, that shows via tuft testing the Porsche rear spoiler doing exactly what I state.



I haven't seen a tech paper on the Taycan yet, but I'd be pretty sure we'll find it has a very good underfloor that develops low pressure.



It doesn't need a vehicle dynamics expert to understand that if you have measurable downforce, and the car's mass has barely increased, then tyre grip is improved.

*The 'tone' of your voice takes on the color of anything but humble.Have you listened to yourself?
*My statements about lift are grounded in fluid mechanics. And specifically with respect to road vehicles.
*Let me know when Handley Page,Jaguar,Rolls-Royce,or Bentley debut a Cd 0.12 automobile under Bernard's tutelage and he'll have my attention.
*If you're looking under the car for stability,you're looking on the wrong side of the car. It's all about the roof profile.
*Why are you introducing downforce? Are you trying to finish off the Great Barrier Reef all by yourself?

[aerohead]

Originally Posted by JulianEdgar

What separation on the roof of the Cayenne? Have you looked at the wind tunnel video with smoke streams produced by Porsche? Just as one would expect, it doesn't show any separation on the roof.

There's no reason in discussing it until you demonstrate a handle on the Bernoulli Theorem.Bernard should have told you that.

[aerohead]

Originally Posted by California98Civic

I love that spoiler. I also suspect that the roof spoiler the OP is describing might not be so much to let air escape as it is for "tuning" the flow in some way. For example, Subaru apparently spent a lot of time and money tuning the position of those silly looking vortex generators you see on the STi from a fee years ago. The goal, I read, was to direct flow to the substantial wing on the rear decklid.

Ford's patent is available.There's no reason to speculate on it's premise,you can read it directly from the inventors.