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Old Oct 10, 2012, 03:42 AM
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The control surface endplates are interesting but don’t appear to lend themselves to simple analysis. The purpose of an aileron is to produce a rolling moment by changing the loading along the span. Any change in the span loading has to be accompanied by a change in the vorticity / circulation carried along the span. The presence of an end plate can’t change the fact that a change in the span loading must result in vorticity /circulation being shed into the wake (if the endplate were to completely “block” vortex shedding at the aileron tip, it would also make the aileron completely ineffective).

Given that the end plates can’t block the vorticity shedding, all they can do is redistribute it. If the redistribution they provide makes the resulting span loading closer to elliptic, they should reduce the induced drag due to aileron deflection. The question then becomes: does this benefit outweigh the profile drag cost? Given that the profile drag of an end plate is always present, and its potential induced drag savings would only come into play during aileron (or partial-span flap) deflection, their prospect for providing overall performance benefit is dubious.

My limited experience with vortex lattice codes suggests that they are poorly equipped to explore this configuration. I have had very little success trying to directly model the circulation in the vicinity of a flap or aileron break with a vortex lattice code. If I understand AVL’s implementation, control deflection is approximated by “normal vector tilting”. I have found this approach to more accuratley predict the span loading than dircet analysis of the actual control surface geometry. Unfortunatley, this approach prevents comparing the endplate case to the no-endplate case. Would useful comparison really require a full-blown experimental or Navier-Stokes analysis?
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