Rear diffuser?

[Phase]

https://youtu.be/Mi5NgRyAqt4

https://youtu.be/Zq2KjcNE50c

two videos showing a flat floor isnt necessery. it helps a little and is better than a dirty floor, but the diffuser helps all cars

[aerohead]

I don't know anything about this person.
I don't know anything about the CFD he uses.
The models he depicts do not represent any 'reality' I've ever experienced.
Perhaps, when I have nothing else to do, I can spend some time vetting him, but until then , I find his conclusions highly dubious.
There's some 'context' associated with his presentation, however there's no transparency provided in its content.

[Phase]

Originally Posted by aerohead

I don't know anything about this person.
I don't know anything about the CFD he uses.
The models he depicts do not represent any 'reality' I've ever experienced.
Perhaps, when I have nothing else to do, I can spend some time vetting him, but until then , I find his conclusions highly dubious.
There's some 'context' associated with his presentation, however there's no transparency provided in its content.

Those are two different people doing two different tests

Bottom line is yes, a flat floor is best, but you don’t need a flat floor for a rear diffuser to work

[Blacktree]

Originally Posted by aerohead

I don't know anything about this person.
I don't know anything about the CFD he uses.

The first video is someone I'm familiar with. He does this stuff (aerodynamics engineering) for a living. So there's a pretty good chance he actually knows wtf he's talking about.

The second video, I'm not familiar with. So I can't comment.

[aerohead]

Originally Posted by Phase

Those are two different people doing two different tests

Bottom line is yes, a flat floor is best, but you don’t need a flat floor for a rear diffuser to work

It flies in the face of all previously published foundational research. And I don't understand the rush to dismiss what, up to now has been considered 'settled science.'
So, like something the late Carl Sagan might say, it would require a remarkable argument.

[aerohead]

Originally Posted by Blacktree

The first video is someone I'm familiar with. He does this stuff (aerodynamics engineering) for a living. So there's a pretty good chance he actually knows wtf he's talking about.

The second video, I'm not familiar with. So I can't comment.

When I can, I'll try and dig up a portfolio on the guy.
Some CFD I've seen, like Air Shaper, produces quanta which doesn't resonate within this universe. Orders of magnitude.

[Phase]

Originally Posted by aerohead

It flies in the face of all previously published foundational research. And I don't understand the rush to dismiss what, up to now has been considered 'settled science.'
So, like something the late Carl Sagan might say, it would require a remarkable argument.

i mean its not as perfect as an EV, but other than the rear section, it seems like its pretty streamlined for an underside

[aerohead]

Here's a link to Munich's model:
https://www.researchgate.net/profile...r-OpenFOAM.pdf
For the notchback smooth underbody model, CFD was 4.26% different than wind tunnel.
Same car, but with detailed underbody, the CFD was 11.18% different than the wind tunnel model.

[aerohead]

I went to the Munich, Germany site.
I reverse-engineered an estimated frontal area.
I reverse-engineered the VERSUS ENGINEERING test velocity.
Using Munich's drag coefficients for the wind tunnel tested-model, I reverse-engineered for VERSUS's velocity.
With their own numbers, I calculated that the 'smooth-bellied' notchback with diffuser would have 39.1 fewer counts than the 'dirty-bellied' notchback with diffuser, making 13.82% lower drag.
With only the smooth belly and diffuser, the IONIQ might hit it's target of Cd 0.20.

[Phase]

Originally Posted by aerohead

I went to the Munich, Germany site.
I reverse-engineered an estimated frontal area.
I reverse-engineered the VERSUS ENGINEERING test velocity.
Using Munich's drag coefficients for the wind tunnel tested-model, I reverse-engineered for VERSUS's velocity.
With their own numbers, I calculated that the 'smooth-bellied' notchback with diffuser would have 39.1 fewer counts than the 'dirty-bellied' notchback with diffuser, making 13.82% lower drag.
With only the smooth belly and diffuser, the IONIQ might hit it's target of Cd 0.20.

Why’s the Ioniq ev got the same or higher CD then if that has a smooth flat under body and a mini rear diffuser? That’s what I don’t get

I’m pretty worried about cooling when trying to cover the underbody mufflers and exhaust pipes