McLaren MP4-29 Mercedes

[Holm86]

Seems like all the 'experts' agree with me that the tubercles is there to reattach the boundary layer when drs has been activated.

[trinidefender]

Seems like all the 'experts' agree with me that the tubercles is there to reattach the boundary layer when drs has been activated.

Would hesitate to make that assumption. Would rather say that is a secondary function of it. Honestly doesn't take very long for airflow to reattach to a wing once the wing is brought back into its operating range. If you have ever flown a small plane and then stalled it. Almost as soon as you put the nose down you can feel the wing starting to work again and providing lift.

If the tubercles were only there to help the flow reattach after DRS then the wing would work worse in all other conditions. Think about it, teams have a defined box to work with, that means adding these bumps would slightly reduce the surface area of the wing. Therefore it makes sense that the bumps are there for a different function such as reducing spanwise flow and to allow the wing to run at a higher angle of attack.

[Crucial_Xtreme]

Would hesitate to make that assumption. Would rather say that is a secondary function of it. Honestly doesn't take very long for airflow to reattach to a wing once the wing is brought back into its operating range..

It can take long enough. A delay in re-attachment of airflow was one of the reasons the F2012 struggled so much especially on corner entry. I'm not saying this is the only benefit of the tubercles, but I think it's safe to say it's one of the main reasons it was introduced.

[trinidefender]

Would hesitate to make that assumption. Would rather say that is a secondary function of it. Honestly doesn't take very long for airflow to reattach to a wing once the wing is brought back into its operating range..

It can take long enough. A delay in re-attachment of airflow was one of the reasons the F2012 struggled so much especially on corner entry. I'm not saying this is the only benefit of the tubercles, but I think it's safe to say it's one of the main reasons it was introduced.

That would make sense for the F2012. However do you think the McLaren is considered one of the more unstable cars under braking for this to be a main design condition for the new rear wing? I haven't had the chance to watch many of the races this year so i wouldn't be able to judge properly.

[mclaren_mircea]

Would hesitate to make that assumption. Would rather say that is a secondary function of it. Honestly doesn't take very long for airflow to reattach to a wing once the wing is brought back into its operating range..

It can take long enough. A delay in re-attachment of airflow was one of the reasons the F2012 struggled so much especially on corner entry. I'm not saying this is the only benefit of the tubercles, but I think it's safe to say it's one of the main reasons it was introduced.

That would make sense for the F2012. However do you think the McLaren is considered one of the more unstable cars under braking for this to be a main design condition for the new rear wing? I haven't had the chance to watch many of the races this year so i wouldn't be able to judge properly.

Following live.timing on skysports during FP2 in Hungary, one of the conclusions of the moderatos was this: "the improved Mclaren is one of the most stable cars under braking"

[bhall II]

Given the lack of upwash from a beam wing, it may be that McLaren's solution doesn't necessarily address a specific issue with their car as much as it tackles an issue with the new regulations in general. If other teams copy this design, which should be a relatively straight-forward proposition since there aren't really any downstream consequences, we'll get a better idea.

And remember: Gary Anderson tends to be a bit short sighted with his "analyses." While I agree with what he's said here - first proposed by Holm-boy, it should be said - that explanation doesn't preclude other effects.

[Lycoming]

Seems like all the 'experts' agree with me that the tubercles is there to reattach the boundary layer when drs has been activated.

Would hesitate to make that assumption. Would rather say that is a secondary function of it. Honestly doesn't take very long for airflow to reattach to a wing once the wing is brought back into its operating range. If you have ever flown a small plane and then stalled it. Almost as soon as you put the nose down you can feel the wing starting to work again and providing lift.

Light aircraft wings are different from the highly cambered wings F1 cars use. Wings like this sometimes exhibit significant "hysteresis", in which if you angle it past stall and then reduce the angle of attack, it doesn't fully regain it's original performance. If you look at the wind tunnel test data from the UIUC airfoil database, some of the high-lift airfoils exhibit this.

Of course that's not necessarily the only reason they're there, but just pointing out that reattachment is not necessarily all that quick.

Therefore it makes sense that the bumps are there for a different function such as reducing spanwise flow and to allow the wing to run at a higher angle of attack.

There are better ways of reducing spanwise flow, and running higher angle of attack would only be helpful on the high downforce tracks, although they probably do allow that.

[trinidefender]

Seems like all the 'experts' agree with me that the tubercles is there to reattach the boundary layer when drs has been activated.

Would hesitate to make that assumption. Would rather say that is a secondary function of it. Honestly doesn't take very long for airflow to reattach to a wing once the wing is brought back into its operating range. If you have ever flown a small plane and then stalled it. Almost as soon as you put the nose down you can feel the wing starting to work again and providing lift.

Light aircraft wings are different from the highly cambered wings F1 cars use. Wings like this sometimes exhibit significant "hysteresis", in which if you angle it past stall and then reduce the angle of attack, it doesn't fully regain it's original performance. If you look at the wind tunnel test data from the UIUC airfoil database, some of the high-lift airfoils exhibit this.

Of course that's not necessarily the only reason they're there, but just pointing out that reattachment is not necessarily all that quick.

Therefore it makes sense that the bumps are there for a different function such as reducing spanwise flow and to allow the wing to run at a higher angle of attack.

There are better ways of reducing spanwise flow, and running higher angle of attack would only be helpful on the high downforce tracks, although they probably do allow that.

Yes I have heard what you are saying to be true about sometimes it takes a bit for flow to re-attach to wings once brought back in to their operating range on highly cambered wings so that is very probable. However what strikes me as odd was that if it were this large a problem then you would see drivers up and down the pit lane complaining of horrible braking stability however since the introduction of DRS you don't hear this much more than you did before indicating that DRS isn't disrupting re-attachment of airflow to much.

About the second part, let me rephrase my original statement to it allows a better L/D of such a highly cambered hard working wing such as the rear wing.

Running a higher angle of attack may actually have some balance benefits in the case of the mp4-29. When McLaren introduced the new front wing Button (I think it was him) was saying that now the front downforce was to high relative to the rear of the car. Maybe the increased downforce created by the higher AoA of the new rear wing (if it indeed does allow a higher AoA) helps to balance out the increased front down force producing a net gain all around and a more balanced car when it comes to flow separation on the rear wing running over bumps (vibrations and jumping of a wing can cause flow separation) and upon closing of the DRS flap.

[Lycoming]

The paper I saw many years ago in which a student windtunnel tested tubercles showed slightly worse L/D overall and also did not allow for a higher Cl, it only allowed the wing to operate at a higher angle of attack without a huge dropoff in Cl.

But that was for a single element symmetric airfoil, he never tested a highly cambered slotted airfoil.

Maybe I should go find this paper and post it here...

[bhall II]

By interpreting the skin friction lines in the separation region in terms of critical points we were able to
infer that tubercles built by chord variations and constant thickness act as vortex generators. On periodic
wings they tend to reduce Clmax but mitigate the stall, by sustaining higher levels of lift for higher angles
of attack. Tubercles may be used successfully to energize the flow at critical span-wise locations, potentially
improving the outboard stall characteristics as in the case of Miklosovic’s whale flipper model. Our results
confirm Hensen’s observation that tubercles might be detrimental at low Reynolds numbers.

We have also shown that a variation in thickness along the span, which creates channels of sorts along the
chord, can be used to break up the separation regions and create spanwise fences, which can increase Clmax.
Our observations indicate that a fully three-dimesional shape optimization is necessary to design tubercles
with higher performance; this is the subject of our ongoing research. Also, recalling that the humpback is
known for performing tight turn maneuvering, an in depth assessment of tubercle performance in dynamic
stall conditions seems de rigueur.

[emmepi27]

Very beautiful pic of Amus! =D>

[mikeerfol]

Video - maximising the McLaren MP4-29

http://www.formula1.com/news/technical/2014/0/1211.html

[Thatsnotgonewell]

I'm a little surprised with all this work on rear wing details that McLaren are still using a simple center support spar rather than a swan neck. Maybe they were looking for consistency rather than pure performance?

[Lycoming]

Most likely they believe it's not worth their time.

[trinidefender]

I'm a little surprised with all this work on rear wing details that McLaren are still using a simple center support spar rather than a swan neck. Maybe they were looking for consistency rather than pure performance?

Also remember that the lower portion of their rear wing end plates are much smaller than most teams because of their weird suspension arms. Probably means that more force has to be taken by the rear wing support and maybe a swan neck simply can't support that.