Vortex pair of coaxial helical filaments

Possible existence of vortex pairs of coaxially rotating helical filaments with circulation in the opposite directions is theoretically studied. Such pairs are generated, e.g., by a rotating blade of the rotor with identical intensities of the tip and shifted axial vortices. Conditions that ensure uniform rotation of the vortex pair of helical filaments are found, which is needed for modeling vortex wakes behind rotor blades.