Diffuser Profile - Convex or Concave?

[shelly]

IIRC that feature was almost standard on every F1 car before the 2009 rule change.
It was related to a rule that imposed minimum radius for the transition from the flat floor to the diffuser. I think it is not adopted now because the ruling has changed.

I agree with gixxer: when cfd and wt give different result, it's not a matter of asking which is wrong - there's a big chance both results are wrong.

[hardingfv32]

Now if the boundary layer buildup exceeds what you calculate it to be (and this happens ALL the time) you kind of scratch your head, but depending on budgets and time you pursue what you must to get a car ready and performing at the best you can with the tools and money you have. Especially when you have a rolling floor, everyone thinks that fixes everything.

Someone I really look up to once told me that you never really understand the car until you designed and tested the wind tunnel as well.

If your CFD and your tunnel data don't converge, what do you trust? A mathematical system designed around giving the same results as a wind tunnel or a wind tunnel?

Nobody else copied it, it only worked in one tunnel. Might explain their car's performance if it were true. DId that feature appear on the new car after they pulled out?

In my vivid imagination F1 tunnels are so amazing they always give perfect values but reality may be a bit different. ;)

I think you paint too negative a picture, especially for those who have no actual tunnel experience. I don't think any of the issues you bring up are unknown to most major tunnel operators. Chances are good that many of the solutions are proprietary, so in fact they are not issues at all. We don't even have a good idea how much is spent doing tunnel development.

In the end I think you develop a numbers that represents the accuracy of the correlation between CFD, WT and actual track results. You view your results through the lens of these numbers.

Brian

[gixxer_drew]

Im throwing ideas out for consideration not absolute conclusions.

The way it was laid out was that one team had a part that nobody else had. Then thinking through calculated boundary layer over that short of a run and something didn't add up if the thing is to break up boundary. Doesn't mean it isnt something else, I presented a few different possibilities I would want to investigate, could be a sea of things.

Only one thing I suggested for investigation was a potential wind tunnel problem. If it was a rules thing, thats fine, but short of that... something is odd about that part. I am basing that on intuition and experience. Assign value to that at will.

The "why" is still the question, but it is definitely striking me as odd. Also I would disagree about these issues being "known" because I find problems in probably the majority of tunnels I use and have to just work around them. Presumably F1 tunnels are better though, I have no experience with them.

My real point in all of this is not to conclude that such a device will work well for you because it was on an F1 car.

[gixxer_drew]

Got a couple photos of the honda diffuser from 2007 season. I have no way to get access to the anything more recent than the photo which was posted before with the step.




I'm trying to find out more about the step and I'll ask if I can talk about it publicly.

[ringo]

Here we have 3 curves. No step on this one.