SymmetricalDataSecurity: Running Computational fluid dynamics on leaked 2021 Williams F1 CAD

Sunday, April 25, 2021

Running Computational fluid dynamics on leaked 2021 Williams F1 CAD

Thanks to some clever people I was able to get a CAD model of the current 2021 Williams F1 car — that’s not something that happens every day, so of course I had to run CFD on it.

The suspension positions on the model were set up for around 2.08 degrees rake, so that’s how I’ve run it for the baseline. To make it easier on myself I’ve also replaced the wheels and tires with the geometry from my MVRC car (see my previous post). The only problematic geometry was the brake ducts which were in pretty bad shape, so I went ahead and made some simplified parts to replace them — I especially wanted to capture the winglets on the rear duct:

The other notable issue was that the diffuser did not have any strakes. I may try to add some in later but for now I’m running without them.

Here are the results:

CD	CL	L/D	CLF	CLR
1.746	-4.598	-2.634	-2.004	-2.594

Baseline Results, 2.08 deg rake. A = 1 m^2

CL Front Wing	CL Body	CL Rear Wing	CD Front Wing	CD Body	CD Rear Wing	CL/CD Front Wing	CL/CD Body	CL/CD Rear Wing
-1.194	-2.379	-1.158	0.169	0.573	0.402	-7.065	-4.152	-2.881

Breakdown by Part

The drag looks to be rather high, but otherwise I think these numbers are at least in the right ballpark, given the limitations of the CFD setup (there are clearly areas where the mesh is limiting the performance). For reference, when I tried to match my lapsim program to telemetry from the 2020 Spanish GP, I arrived at CL = -5.421 and CD = 1.150 (perhaps more about that in another post). Balance also looks reasonable at 43.6% front, a few percent rearward of the dry weight distribution (45.5% for 2021).

Naturally, these numbers change dramatically with ride height. I’ve begun running a ride height map and I’ll make a separate post about that when all the runs are finished.

Below are a series of images, enjoy:

Surface Velocity. Lots of flow going around the sidepod to the floor edge.
Flow nicely attached over the sidepods and sweeping down towards the diffuser.
Interesting flow split between center and outboard of the floor as it comes through the bargeboards.

Surface pressure. Note the low pressure regions on top of the front suspension, halo, and sidepod winglets as the front wing upwash is re-directed down towards the rear of the car.
Surface pressure.
Lots of performance coming from the leading edge of the floor.
Surface pressure.

Vortices on the upper surface.
Vorticies
Good shot here of the cape’s function. Rolling up a vortex which interacts with the bargeboards and ultimately travels the length of the floor.
Also interesting to note the floor edge vortex which seems to pull a lot of high-energy flow into the diffuser.

Velocity slice at the ground plane. Bargeboard working hard to push the front tire wake outboard.
Velocity slice on the top side of the floor. Notice the high speed flow between the diffuser and rear tire.
Diffuser throwing air outboard behind the rear tire.

Centerline velocity slice
Some separation on the front suspension arms, but lots of clean air headed to the rear wing.
Further outboard the flow is better aligned with the suspension.
Sloped sidepod directing flow down to the floor.