David Findlay wrote: > Curt Olson wrote: > > So for instance if you want to try Andy's YASim 747 model, and check > > out his alternate (blade element-ish) approach to modeling the flight > > dynamics > > So what exactly does blade element-ish mean? Is this sorta like a realtime > digital wind tunnel sorta thing? Thanks,
Sorta. Blade element is a term from propeller theory, but the basic idea is the same. The airframe is broken up into a bunch of "surface" objects, each of which gets an independant force calculation. Since they're at different positions, they will have different velocities due to aircraft rotation or orientation. So you get some cool stuff "for free" as it were: asymmetric stalls, where one wing stalls before the other and puts the aircraft into a nasty orientation or spin(-like state); or adverse yaw -- crank the ailerons hard to one side and the aircraft will yaw to oppose the turn due to the extra drag on the upward-moving airleron. Eventually (hopefully soon), this will be extended to support turbulence and wash effects at each surface. There are some performance worries there, though, since if each surface depends on the wash effects of all the others you go from O(N) to O(N^2) in the number of surfaces. I think it'll work, but might require some surgery. Actually, the coolest feature of YASim (well, the one I'm most proud of) isn't the low-level simulation mechanism. It's the high level performance matcher/solver. In a YASim configuration file, you simply ask for "a plane that weighs so much, cruises at this speed, has this big an engine and has an approach speed of XXX knots at NN degrees AoA" -- and that's what you get. This radically reduces the amount of "tweaking" that needs to be done. Climb rates tend to be right about where they should be, etc... There's still lots of tweaking (or can be -- I haven't really tuned the existing models much), but you start out with a working aircraft from the very beginning. Andy -- Andrew J. Ross NextBus Information Systems Senior Software Engineer Emeryville, CA [EMAIL PROTECTED] http://www.nextbus.com "Men go crazy in conflagrations. They only get better one by one." - Sting (misquoted) _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
