xpensive wrote:@JT: I still believe you've got your terminology confused, "physical" is by no means a synonym to "analytical".
I don't think I'm confused at all. In the world I work in - the world of vehicle dynamics, tire data, etc - they are used synonymously. That's just how it is. Don't know what else to say. You can have an empirical / curve fitted / test data driven model... or a physical / theoretical / analytical model. Applies to vehicle characterization as much as it applies to tire characterization. You can have a suspension which is defined by curve-fitted K&C data, or you can have one that's computed on-the-go by a multibody simulation. Each have their own strengths and weaknesses.
Beyond that, this is so past the point of this thread that it borders on asinine. But this seems to be the case every time you bring something up - it's not to further the value of the thread through meaningful discussion - it's prodding at trivialities and unproductive BS. Like I say, this is the world I work in.. and I like to shed some light on things from time to time using what public domain data as I can. If you're not interested in in it, then go do something else rather than derail discussion.
On to the matter at hand...
gato azul wrote:So unless, we define the term "speed" a bit more precisely in the OT quoted statement, I would be careful, to dismiss the statement out of hand or call it BS.
Trimming this quote down quite a bit, but to me... it effectively makes no difference whether you're thinking of speed with sliding velocity or whatever.
For one, if you're using something like an industry standard Magic Formula model... the post-saturation "sliding" characteristic of the tread is already implicitly defined in the model by the lateral and longitudinal force shape factors. Don't even have to worry about it - it's already built in. With regard to physical models - I don't worry about them because for the vast, vast majority of end users you're just not going to have pressure / velocity / temperature sensitive data so it's totally impractical. Besides if you're way post saturation in your simulation (i.e. spinning out or brutally beating up on the fronts) you have bigger issues to worry about. I leave that realm to the video gamers.
Then with regard to tire rotational speed - again, there's a reason why even in the latest and greatest empirical models after 15+ years of development, there's not even a single parameter given to it (turnslip and parking maneuver behavior excepted - but that's not exactly of concern in racing). Just completely drowned out by the other state variables. Maybe that's just my own working experience.. after going through gigs and gigs of data, some things are more on my radar than others.
More to the point, even if you DO add it in - it doesn't mean you're going to get any value out of it. In my earlier post - your vehicle speed at any point on the racetrack is what it is. Not going to change by a dramatic amount. I'd rather focus on the things that ARE in my control, namely load, camber, slip, and inflation.
It's very easy to get into the mindset that just because something is there that you have to model it. Or that racing is all about "all the little things" and that's what's most useful to track down. You can spend the time to make your model more complex and then still arrive at the same end answer; you've added cost and complexity but it hasn't been value-added work. Given that my experience in racing has been that you are dramatically time limited in how much you can get done for a race, I see MUCH more value in getting a "close enough" answer today, rather than a marginally more precise or complete answer several days or a week from now.
My MO is to be as effective and impactful as you can, use the simplest models or predictive tools as you can - not the most complicated or involved.