David Megginson wrote: > Ralph Jones writes: > > It would, indeed, be nice to have a vertical velocity model for simulating > > soaring flight. I'm still trying to run down stability derivatives for my > > sailplane! > > It will be easy to allow you to specify up- or down-drafts for > specific areas; it will be much harder to have FlightGear figure them > out itself, but it might still be doable.
Doing this "right", of course, is a job for 2000 CPU supercomputers. But it might be OK for use to cheat a little. How about this: Look at the wind over ground at the current location. Calculate the up- or down-slope of the ground in that direction. Figure out an up or downdraft based on the amount of air that must be vertically displaced. Look at the amount of sunlight falling on the ground, maybe combined with an albedo value based on the terrain type and a cloud layer effect for shadow. This gives you a heat flux. Combine that with the air temperature on the ground to figure out how much air needs to be flowing upward to carry this heat away (this is going to require some hand waving about the uplift velocity as a function of temperature difference). This number should add to the turbulence as well. This won't take into account a whole range of second-order effects, like nearby mountain ridges, etc... But it might match reasonably well to a sailplane pilots intuition about where the updrafts "should" be. Not being a sailplane pilot, I couldn't say. :) 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
