The change in how air behaves over the top of the sidepod may appear to be quite subtle, which is why teams have long played down the significance of the performance gain from this area of the car.
However, as McLaren team principal Andrea Stella has explained, the real gains from shifting sidepods are far more to do with how the shape of the sidepods interacts with the rest of the car rather than just what is happening in this area.
He suggests that the biggest advantage of going the downwash route is the width and shape of the undercut, which he suggests offers opportunities through the shaping of the floor to produce a less amplified version of the benefit that skirts gave back in the previous ground effect era.
Asked by Autosport to explain the key upside from downwash, Stella said: "Yeah, I wouldn't say simply downwash. I would say wide sidepods. I think it's actually the primary concept that seems to interact very well with the floor. Because the sidepods in simple terms, act a little bit like mini skirts.
"Aerodynamically these wide sidepods help the suction in the floor. So that's the concept that it looks like you can't do without if you want to maximise the suction in the floor and the load on the car. And it's very clear that everyone is converging in that direction."
Stella's reference to 'mini skirts' is about the way that the floor was sealed in the original ground effect era through the use of skirts along the bottom of the sidepods, which effectively created an area of super low pressure under the car to boost downforce.
While such a seal is not possible now, because of minimum floor height restrictions, the general theory behind what is going on with air underneath the car still holds true.
The wider sidepods, as Stella refers to them, can therefore be seen as a means to deal with the wake turbulence created by the front wheels, much like the deflectors did under the previous regulations, albeit not with as much design freedom to 'off body' the airflow.
This continues down the sidepod's surface, helping with the floor edge and having an influence over the rear wheel wake, reducing the influence it can have on the diffuser.
The solution of course is not as effective as some of the extreme solutions seen on cars in the 1980s, but any gain you can find in F1 these days is important when the gaps between teams are so small.
Source: Autosport