Greg Locock wrote: ↑19 Dec 2020, 23:35
Couple of things. Mr Edgar is perhaps not a great theortician in the world of aero. His most famous article in Silicon Chip was on how to run a garage sale.
Cost of correlation data is a brilliant question which I've never thought about. My off topic response, as it is vehicle dynamics, suggests we are talking about $86000 per vehicle. This is one reason why 'they' want to get rid of prototypes. Admittedly most of that would have to be done anyway if we were just developing the car directly rather than as a sim.
It adds up. To even do 1D simulation right (like within 1%) , you need to have a test engine and equipment to record and tweak the burn models, dyno data. A flowbench that can flow up to 100 inH2O can be used to help develop the Cd tables, use Spintron data to measure valvetrain flex and changes with rpm, as well as use it to develop the friction models, etc. All that alone could be $60-80k in work, and you still have to go back and forth... say you changed piston ring design... that may require going back and measuring the change to tweak your friction model, etc.
I have one now that is about 5%, but we have dyno data, flowbench data, in cylinder pressure data, etc. The shape of the curve is spot on though, so not too worried about exact numbers (quality of real world measurements), and just looking at overall trends and changes to the curve. If you take the cost of development of the engine to the point we had quality enough data, you’re almost in $40k. And this is for an amateur effort with a vintage race application, and people directly involved in this aren’t even charging for their time.
I could start from scratch without any of this and produce a curve that looks good and is close-ish (10% or so), but I would have no idea where I was at without real world data.
For aero, look at the resources Ferrari has and they still struggle with it.