Certain interactions, for example BVI are such that the interacting tip vortex
filament with the blade is nearly parallel to the rotor blade. The resulting interaction can then
be idealized as a series of two-dimensional interactions between the blade section and a two
dimensional vortex. A two-dimensional section of the rotor blade airfoil undergoing BVI is shown
as a schematic. along with the typical vortex induced velocity. The velocity induced by