The T wing is another one of those divisive 2017 aero devices, opened up by a hole in the rulebook. Personally, I was a big fan as we got to have a really prominent display of difference in the way teams approached it. On the other hand, many people have said they look ridiculous, which is also a fair point. But we aren't really concerned about the looks here on DriveTribe Car Tech, it's all about the function. So what do they do?
McLaren commonly runs this coathanger style T-wing.
First and foremost, the T-wing is a highly efficient generator of downforce. Note: 'efficient', not 'massive' - it will never generate a huge amount of total vehicle downforce as it is so small. The T-wing has a high aspect ratio, which is the ratio of its span to its chord (or depth). I won't go into the details, but higher aspect ratio wings are typically more efficient. This means their drag penalty is low for the amount of lift (or downforce) they generate. Hence, the T-wing can be thought of as downforce with minimum drag penalty, certainly better than the rear wing in terms of efficiency, and this is why you now see them across the grid.
Want to see something with a similar aspect ratio to a T-Wing? Try a glider, one of the most efficient types of aircraft.
But, there's a problem. A lot of people (Commentators etc., not team engineers) have said the T-wing is there to manage and clean the airflow to the rear wing, but this isn't explicitly true. For a start, the entire centre span of the T-wing leaves upwashed flow, which is then pushed further up by the wing, so there is no direct interaction of the downstream flow at all with the majority of the wing (wait for the video below if you're struggling).
The upwash of the T-wing will help support the rear wing to an extent, and there will be slight interactions between the pressure fields of the T-wing and rear wing due to their proximity. However, the tip vortices of the T-wing are pulled around by the rear wing vortices and merge with them, and this does (on my full car geometry anyway) increase the drag on the second element of the rear wing. There are more details on the specifics of this in the video at the bottom.
Ferrari ran a four element T wing for quite a few races, the slot gap is large and the total angle of attack low, indicating that they are not functioning entirely in the same manner as a traditional multi-element wing.
So, why the double deck T-wing? Well, there's a few reasons why you would want to go down this path. For one, connecting the tips of the wings can help with structural rigidity. While a bit of aeroelasticity (flexing with airflow) can be helpful, you don't want your wing fluttering like crazy as it will diminish its performance, so it is good to have more control over the rigidity here. Ideally we would just like the wing to twist back or slot gaps to close (if total camber is high) as speed increases to drop drag, but we still want our bending strength to be good to help a bit with flutter.
Williams has the craziest T-wings out there on the grid, especially when it comes to the high downforce tracks.
There are also aerodynamic benefits. Obviously, with sufficiently spaced wings double the wing = double the downforce. This doesn't quite work out in practice as there is interaction between the pressure fields of the two wings, but there is still a benefit. Having two joined wings also means you can distribute the downforce across them, and have the join acting as an endplate, so the wingtip vortex strength can be decreased. This will have two benefits: one, the T-wing will become locally more efficient. And two, the rear wing will be less affected by the T-wing vortex. These are just some of the reasons most teams have adopted multi-tier T-wings.
For more details and an analysis of T-Wings (with numbers), check out the video below!
Kyle Forster is a qualified Aerodynamicist, race car engineer, and the man behind JKF Aero, a firm that offers a variety of aerodynamic consultancy services for racing purposes. If you have any questions for Kyle or have any suggestions for future videos, drop them in the comments below!