HALF-PLOW VORTEX GENERATORS FOR ROTORCRAFT BLADES FOR REDUCING BLADE-VORTEX INTERACTION NOISE

摘要

In one embodiment for a helicopter main rotor assembly, a half-plow vortex generator is mounted in combination with the upper aerodynamic surface of each main rotor blade and is operative to generate a primary corotating vortex of sufficient strength to interact with and dissipate the tip vortex generated by the same main rotor blade, thereby reducing blade-vortex interaction noise radiating from the helicopter main rotor assembly. The half-plow vortex generator has a right triangular planform configuration defined by a length, a width, and an apex angle. The three-dimensional configuration of the vortex generator is further defined by an apex height. The apex height is the primary determinant of the strength of the generated primary corotating vortex and is defined in terms of the magnitude of the local chord where the vortex generator is mounted. The apex height preferably has a magnitude within the range of about 0.01 to about 0.08 of the magnitude of the local chord. The length, width, and apex angle are secondary determinants of the strength of the primary corotating vortex generated by the half-plow vortex generator. The length and width of the vortex generator are also defined in terms of the magnitude of the local chord, the length preferably having a magnitude within the range of about one-fourth to about one-half of the magnitude off the local chord and the width preferably having a value of about one-third of the length of the vortex generator. The apex angle preferably has a value within the range of about twenty to about thirty degrees. The mounting site for the half-plow vortex generator is defined in terms of the length of the local and tip chords. The vortex generator is mounted inboardly from the tip of the main rotor blade a spanwise distance having a magnitude preferably within the range of about one-half to about equal to the tip chord length and is mounted with the length thereof in substantial alignment with the local chord. The apex of the vortex generator is mounted inwardly from the leading edge of the main rotor blade by a chordal distance having a magnitude of about one-quarter of the magnitude of the local chord.