On Wed, 2002-06-05 at 20:54, Andy Ross wrote: > Tony Peden wrote: > > Induced drag is a function of the vortices surrounding the wing. > > Those vortices vary in strength with lift, not angle of attack. > > Not so. The induced drag of an aircraft in high-speed cruise is much > lower than an aircraft in level flight at stall speed.
I probably used lift where I should have used CL. So, at cruise, the dynamic pressure is high and the CL required much lower than at approach speeds where the dynamic pressure is relatively low. Induced drag goes with CL^2 and CL doesn't change much across a flap transition. The lift in > these situations is the same (and equal to weight, of course). Think > about it: if induced drag depended solely on lift, there would be no > such thing as the "back side" of the power curve. Drag would go > asymptotically to some constant as airspeed dropped to zero -- that > clearly isn't right. For real aircraft, drag always increases with > AoA. > > In reality, induced drag looks much more like a function of AoA than > it does a function of lift. Well, in "real" reality induced drag is > just a metaphor; so it isn't "really" a function of anything. > > Maybe you mean to say that induced drag is a function of lift > *coefficient* -- as on a drag polar plot? This is true, but unhelpful > to me. I don't know what the lift coefficient is until I calculate > the AoA. And we're back to where we started. Hmmm... > > 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 -- Tony Peden [EMAIL PROTECTED] We all know Linux is great ... it does infinite loops in 5 seconds. -- attributed to Linus Torvalds _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
