Hi Dean, thanks for the mad props
This is a deep rabbit hole you are peering over the precipice of.
Unfortunately in the world of aero there aren?t many short cuts you can take that yield good results. But making good aerodynamic data available for reasonable money is something a couple of us have been thinking about for a while.
I?ve used many of the CFD codes professionally and I?ve tested at a number of the wind tunnels too. And almost without fail they all produce a different number for the exact same car.
So which one is right? The answer, all of them and none of them.
In order to answer the question of what code/solver/mesh/boundary conditions you should use first we need to know what answer are you looking for?
If you are just trying to measure performance changes to upper body surfaces then a steady state solver with fixed ground might be enough. The mesh dependency really hinges on the local surface geometry at the areas of concern.
If you are looking for safety critical high speed balance. You probably want to consider full transient with rotating wheel and moving ground boundary conditions AND validate it to tunnel data. You wouldn?t use the cheapest shop to weld your safety critical roll cage would you?
Personally I am partial to OpenFoam. It?s free... but the flip side of that is you need to know what you?re doing to avoid poor results.
PM me and we can chat details. Hopefully I can connect you with the right people or software. My suggestion is a blended approach, a couple of big dollar runs for the safety critical knowledge, and cheaper methods for general tuning development.
The last thing I?ll add. No big money solver will get around crap CAD. Your CFD results will only be as good as the initial model you build. More detail (inside and out) always yields more realistic results.