2023 Mercedes-AMG | Petronas F1 Team

[TimW]

Are wind tunnel models of the underfloor scaled down linearly?

Since underfloor downforce is non-linear with ride height, I can imagine that you need to account for this when scaling down the floor, and have some modifiers there for the road to floor distance of the various elements. That would make the scaling itself a complex task, and getting it right not straightforward.

[PlatinumZealot]

Yes the entire car is built to scale. All parts are scaled the same.

This problem has nothing to do with scaling. All teams use as big a scale as they can legally use. 60%.

You could have a badly manufactured wind tunnel part that is the right scale but the fit and finish, and perhaps the flexibilty too is bad. Now that will impact the aerodyamics!

[PhillipM]

I don't think that's right at all, many parts aren't built to scale, or they didn't used to be when I used to have access to Manor, a lot of scaled parts are modified to account for predicted differences at wind tunnel scale vs car scale. Things don't work the same just because you made everything scaled the same.
It's part of why correlation between not just the wind tunnel and the CFD work, but also the full scale results at the track, are so tricky.

[RS200E]

I don't think that's right at all, many parts aren't built to scale, or they didn't used to be when I used to have access to Manor, a lot of scaled parts are modified to account for predicted differences at wind tunnel scale vs car scale. Things don't work the same just because you made everything scaled the same.
It's part of why correlation between not just the wind tunnel and the CFD work, but also the full scale results at the track, are so tricky.

It isn't tricky, they know what they are doing. Most of the time it works out as planned. If this turns out to be the case then it's a rare event.

[PhillipM]

It's tricky enough that every single team runs flowvis and back to back comparisons on track all year to check parts are doing what they think they should. So yes, it's tricky.

[RS200E]

It's tricky enough that every single team runs flowvis and back to back comparisons on track all year to check parts are doing what they think they should. So yes, it's tricky.

It's part of testing and it's part of the sport. So no, it's not tricky. It's the process and it works very well. There's more chance of a fundamental design and upgrade path flaw/wall than the alleged problems mentioned recently.

[PhillipM]

If it wasn't tricky and it was easy nobody would do it. Because they'd bolt on parts and they know they'd work fine.
We wouldn't have Merc scratching their heads about why their concept doesn't work, we wouldn't have Ferrari rear wings nearly collapsing at the first race, we wouldn't have RB repairing their rear wing ever other race last year with duct tape and hope.
We wouldn't have half the grid last year wondering why they were porpoising and all going "Well we never saw that in the tunnel"
So, yes, it is tricky.

[TimW]

I don't think that's right at all, many parts aren't built to scale, or they didn't used to be when I used to have access to Manor, a lot of scaled parts are modified to account for predicted differences at wind tunnel scale vs car scale. Things don't work the same just because you made everything scaled the same.
It's part of why correlation between not just the wind tunnel and the CFD work, but also the full scale results at the track, are so tricky.

Thanks for the insight!

[taperoo2k]

I don't think that's right at all, many parts aren't built to scale, or they didn't used to be when I used to have access to Manor, a lot of scaled parts are modified to account for predicted differences at wind tunnel scale vs car scale. Things don't work the same just because you made everything scaled the same.
It's part of why correlation between not just the wind tunnel and the CFD work, but also the full scale results at the track, are so tricky.

It sounds like this is less about the scale, but more about the tolerances of the models. Even slightly off and it can probably throw you off course unless you detect it and correct the error. But given wind tunnel time is limited for Mercedes then I guess the pressure to deliver models for testing might have caused a problem. Even a tiny mistake in F1 can lead to much bigger problems.

I'd guess if this rumour is correct, it might only be part of the story of the how and the why's behind Mercedes getting the rule changes so badly wrong.

[AR3-GP]

I don't think that's right at all, many parts aren't built to scale, or they didn't used to be when I used to have access to Manor, a lot of scaled parts are modified to account for predicted differences at wind tunnel scale vs car scale. Things don't work the same just because you made everything scaled the same.
It's part of why correlation between not just the wind tunnel and the CFD work, but also the full scale results at the track, are so tricky.

Well the first problem you have is that nothing on the Wind tunnel model deflects with aero load the way full scale parts deflect. So I would be surprised if any team wanted to just scale down the full size concepts and hit ctrl+p. Especially regarding floor edges, front wings, rear wings, and diffusers.

[ringo]

I think they would be able to scale the defflection as well by manipulating the thickness of the scaled down part. Just a guess

[Rodak]

The issue with using a 60% scale model is that air does not react linearly with scale. A vortex at 100% will have different dynamics to a vortex off a 60% part, as the scale of the air is not changing (if you get my drift). It would seem to be complex to model airflow off a 100% model and reduce that to a 60% model with very good correlation; the model would have to reflect the difference in airstream behavior to the 60% model. This is sort of a macro-micro effect. The exact same problems would apply with water flow past a scaled object...... A further constraint is the air speed limit in the wind tunnel, 180 kph.

Honestly, all these conspiracy theory posts sound sort of .... off.

[Zynerji]

With the ruleset, would Mercedes be prevented from putting the W13 in a full sized tunnel to learn fixes for the W14?

[JordanMugen]

The issue with using a 60% scale model is that air does not react linearly with scale. A vortex at 100% will have different dynamics to a vortex off a 60% part, as the scale of the air is not changing (if you get my drift). It would seem to be complex to model airflow off a 100% model and reduce that to a 60% model with very good correlation; the model would have to reflect the difference in airstream behavior to the 60% model. This is sort of a macro-micro effect. The exact same problems would apply with water flow past a scaled object...... A further constraint is the air speed limit in the wind tunnel, 180 kph.

Honestly, all these conspiracy theory posts sound sort of .... off.

I'm not sure that's correct. If the Reynolds number is the same, it should behave the same, no?

It's not like you are comparing different fluids, where you have to match other numbers.

Anyhow Rodak's comment is not something I have ever heard before.

[Rodak]

What I'm suggesting is that as the model percentage is reduced from the original part, things such as surface finish, dimensions, angulation of components, and all the other aspects of the 60% part deviate from full scale in the wind tunnel, so correlation becomes more difficult to the actual part, leading to erroneous data re laminar flow, flow separation, location of vortices, etc. Certainly I could be wrong, but with the limits on wind tunnel air speed and component size, it could be unfortunately easy to lose correlation to real life.