[AndreP]

Hello,

I'm performing a external flow simulation of a simplified version of a Formula One Car, although I'm facing some problems... I've been the last 2 weeks around this, and between some cluster problems and CAD problems, I'm now clueless what I'm doing wrong... But sometimes, after so many days looking at this, I just lose the ability to see the small details! Everything seems fine to me! So here I explain and give further details!

Lenght Of the Car: 5m
Flow Domain: 55m x 22m x 10m

Inlet -> Flow Domain, Velocity Inlet @ 55ms (Boundary Normal)
Outlets -> Flow Domain, Flow Split Outlet
-> Air Intake of the Car, Pressure Outlet @ 0.8781 bar
Walls and Floor -> Defined as Walls with Slip (for now I'm still not modelating the BL on the floor)

Mesh Models: Surface Wrapper, Surface Remesher, Trimmer Mesh & Prism Layer (10mm base)
Physics Models: Realizable K-Epsilon, Steady, Constant Density, Segregated Flow.

26.8 M cells

Volumetric Controls:
Around Air Intake - 7.5 mm
Behing Front Wheels - 15 mm
Around Cockpit - 12.5 mm
Car Wake (Up to 2.5m distance) - 10 mm
Car Wake (Up to 5m distance) - 15 mm
Car Wake (Up to 7.5 distance) - 20 mm
Around the Whole Car - 20 mm

After doing the volume mesh, the following Mesh Quality indicators were plotted (Accordingly with the Help File on "Mesh Quality"):
Cell Quality - All cells above 1e-5
Cell Warpage - All cells above 0.15
Chevron Cells - All cells are 0
Face Validity - All cells above 1
Least Square Quality - All cells above 1e-3
Skewness Angle - 99% of cells bellow 85, there are some between 85 and 163 but I can't see them on regions
Volume Change - All above 0.01

Wall Y+: Majority of the car between 0-30, around air intake goes around 175 (Currently fixing that in the simulations now meshing/running)

But even with a reasonably quality mesh, I'm still facing strange results (Negative Drag Forces, and stupid residuals!). The residuals have the normalization turned off. Here are the following print screen that might help you! I know there's only 360 iterations which is not a lot, but this ran for 24h, and I think it's enough to see that the simulation is not going anywhere good!

Also, I'm having very strange results on EXTREME speed (around 400 ms at the intake) and extreme pressure coefficient, so I'm guessing it might be something on the physics and setup of the simulation!

Could anyone point me what I could potentially look at to make the simulation retrieve good results?

I can provide extra info, just ask me!!!

Residuals: https://imgur.com/Z4HvXpg
Negative Drag / Positive Downforce: https://imgur.com/xNyGVPS
Mesh 1: https://imgur.com/ynakVUK
Mesh 2: https://imgur.com/58Lr6Pw
Mesh 3: https://imgur.com/BWFbmv0
Mesh 4: https://imgur.com/a2fLFJW
Mesh 4 (Contact Patch): https://imgur.com/QzjAQm2
Velocity Plot at Intake: https://imgur.com/rIfqMRO
Pressure Coefficient Plot at Intake: https://imgur.com/rdBtvin
Air Intake Physics Setup: https://imgur.com/Sf5bruM