by Malcolm » Wed Jun 15, 2011 1:30 pm
Yeah there's a lot of simulation programs out there that will be far more advanced than this, Ricardo Wave is a widely used one that we've had quite a lot to do with here, and it's an awesome program but it takes a lot of work and validation to get results that match reality. I imagine that program will be basically a step up from an Excel spreadsheet with resonance calculations based on Helmholtz resonance theory
Probably useful for gaining an understanding of how certain parameters affect the performance of an engine (and how various parameters affect each other), but I wouldn't hold my breath on it "taking the guesswork out of building an engine"
The thing with simulations is that unless are very thorough it is easy to get results that are flat out wrong. You need to have a decent understanding of the theory that describes the system you're analysing, and also understand the assumptions made and how they can affect the results.
As an example, I did a research project a few years back on assessing a lap time simulation program. This program was developed by a software company in the US, sold for around $5K per licence (we got it cheap cheap since it was for educational use), but the assumptions it made essentially made it useless for anything but a select type of cars and racing (namely relatively high downforce cars on courses with quite large radius turns).
One of the specific problems was to do with what happened when you had a wheel lifting off the ground in cornering. The simulation would calculate lateral weight transfer, and the total load on all wheels would sum to the weight of the car (ignoring aero downforce for now). When a wheel came off the ground it would have a negative weight on it, which meant the weight on the other 3 tyres would be greater than the weight of the car. It would ignore the lateral force created by the lifted wheel, but since the other wheels had more weight on them than the weight of the car, they would create more lateral force than they should. The end result was that if the car you were simulating has enough grip to get the inside wheels off the ground then the simulation became unstable and saw ever increasing grip levels the faster it ran around a corner. If you had been blinding running this simulation without knowing what was going on or understanding the theory, you could come out with the belief that a car with a higher centre of gravity or narrower track width (i.e. more prone to lifting the inside wheels off the ground) would be faster, which is the exact opposite of the truth (usually). Sorry about the long winded example, but I think it illustrates my point well.