hardingfv32 wrote:Generally speaking would you say that all the CFD code is generated by the above stated formulas or are there some 'magic numbers' added to allow the CFD code match reality?
The "magic numbers" for CFD are used to correlate "real life" track data to wind tunnel models to CFD results. With the wind tunnel, there are approximations being made for scale and boundary conditions (wall effects, mounting equipment, etc). With CFD there are approximations being made for grid size, turbulence models, and computational convergence.
As others have said, the basis of all CFD is the Navier-Stokes equations. If you could simultaneously solve this set of equations at every single point in space for a sufficiently large volume surrounding an object you could get an exact representation of the "real world" (assuming your CAD model is also exactly matching the real world).
The problem is created because computers are currently not powerful enough to solve the equations at a high enough resolution. Some estimates say at the current rate of increase in computational power, it could still be 100 years before a full aircraft can be modeled by Direct Numerical Simulation (the technical term for using the N-S equations for all scales of computation) in a useable time frame (days instead of years). I'll assume it will be a similar wait for an F1 car because they are fairly complex, even if the Reynold's number is much less than most aircraft. So for the really small scales, they have developed approximation models for the flow and these are called turbulence models. They are a big part of the "magic numbers" you refer to.
Now imagine that every "solution" is at one instant in time, and most everything at an F1 scale fluctuates with time. The flow itself fluctuates with time but so does the geometry (wing flex, steering angle, tire deflection, ride height, etc). So now the CFD needs to be run to find average values across a given time and configuration.
Makes me want to live to be 200 yrs old so I can be around when they start being able to simulate the whole vehicle at high accuracy.