The ongoing saga of Mercedes’ struggles in 2022 saw its first positive upturn at Barcelona. The introduction of a new floor largely banished the car’s previous porpoising-induced limitation.
It still didn’t match the performance levels of Red Bull or Ferrari, but provided a very strong base for the team to build on. The car setup was no longer just about raising the rear ride height (giving up a lot of downforce in the process) until the rebound was under control. With the subfloor operating window so much wider than before, insert, the ride height could be much closer to its design ideal.
Although very restrictive in certain areas, the 2022 technical regulations allow great freedom in the design of the subfloor. The position of the venturi tunnels creating supports on each side is prescribed in relation to the front and rear axle lines and the flat central keel. The expansion ramp at the back of the tunnels is similarly placed in space, but the geometry of the tunnels themselves is pretty much free.
Various incidents on the track and the subsequent craning of the cars, as well as the physical displacement of the floors of the cars in the garages, gave glimpses of some of the designs. The stock floor of the pre-Spanish GP Mercedes appeared to have tunnels with a much lower ceiling than those of the Red Bull. A lower roofed tunnel will in theory produce more downforce as the air is forced to accelerate harder as it squeezes between the road and the smaller gap. It is the low pressure – relative to the ambient air pressure on the upper surfaces of the car, created by the fast moving air in the tunnels, that creates the downforce.
However, if the tunnel is too restrictive, the airflow can become blocked as the air speed increases. Imagine a bucket of water not with an open top but rather a narrow slot through which to fill it. Pour the water too fast and the slot will reach capacity and the excess water will spill out the sides. When this happens with the airflow through an overly restrictive tunnel, downforce is reduced, the rear of the car lifts and the whole porpoising sequence begins.
The expansion ramp at the rear of the tunnel plays an important role in this. Because it increases in volume along its length, it tries to create a vacuum that the air hastens to fill. The beginning of the expansion ramp is where the air pressure is at its lowest before gradually returning to ambient pressure along its length. The steeper the angle of the ramp, the more air will be drawn in – up to a point. The harder it is to pass here, the less prone the front part of the tunnel should be to stalling.
“It was a real racing car. We could set it up and tune it”
So there are two potential stall points. Everything is further complicated by the dynamics of the car. Low ride heights can be simulated, but not the “aerodynamic hysteresis” that inevitably occurs in the real world – the back and forth of different flows through the ground and how they interact with each other at different speeds, roll and pitch angles, etc.
Evidence from the exposed upper part of the new Mercedes floor in Barcelona suggests that the tunnel now has a higher ceiling and a slightly increased angle expansion ramp. The higher ceiling would make downforce less sensitive to ride height, the sharper expansion ramp would help push air through even with the most restrictive ride height.
Lewis Hamilton and George Russell reported a huge improvement in car handling. “It’s the first time we’ve come down the straight without bouncing,” Hamilton said. “We still have some rebound but it’s much better.”
“The car definitely reacts differently to before,” added Russell.
James Vowles, Mercedes’ chief strategist, commented: “It was a car that was truly a real racing car for once. We could configure it, we could tune it, we could play with the settings and it would react in a predictable way…
“It would be wrong to say that the issue of porpoising has disappeared. I’m sure there will be elements that will come back as we build on our understanding and the foundations we laid in Barcelona. But we have taken a definitive step in our understanding and deployment of what we are putting on the right track. We can build on that.