Barcelona F1 test day two

This aero rake on the rear of the Mercedes is measuring the low-pressure areas behind the car that pull airflow under the diffuser, through from underneath the car – and pulls flow around the Coke bottle over the top of the diffuser. It’s crucial to understand the airflow distribution at the back of the car.

Mercedes here is trying to find out the pressure across the car to see if there’s an area where the low pressure is lower than elsewhere. If you can manipulate your airflow to get as good a balance of low pressure behind the car as possible then you are doing a good job. You can’t increase it, but you want the lowest pressure areas connected up to the area you want. That’s what the vanes in the diffuser are about, manipulating it to get the best benefit.

It’s also about how the airflow recovers from a stall when you get the diffuser close to the ground. Normally, the inside part close to the gearbox that’s furthest from the ‘outside world’ gives up first and you want that to recover quickly. An aero rake on the back can tell you about that.

In some ways, what Mercedes was doing here was a waste of time, because it’s using wet tyres. This means the airflow characteristic over the rear tyre is different. But maybe it was simulating diffuser stall with a lower ride height, or checking the impact of the wet tyres. It’s all about what data you get and how you intend to use it. The key is correlating real world data with your CFD model.