Flaperon Modification Effect on Jet-Flap Interaction Noise Reduction for Chevron Nozzles

Jet-flap interaction (JFI) noise can become an important component of far field noise when a flap is immersed in the engine propulsive stream or is in its entrained region, as in approach conditions for under-the-wing engine configurations. We experimentally study the effect of modifying the flaperon, which is a high speed aileron between the inboard and the outboard flaps, at both approach and take-off conditions using scaled models in a free jet. The flaperon modifications are of two types: sawtooth trailing edge and mini vortex generators (vg's). Parametric variations of these two concepts are tested with a round coaxial nozzle and an advanced chevron nozzle, with azimuthally varying fan chevrons, using both far field microphone arrays and phased microphone arrays for source diagnostics purposes. In general, the phased array results corroborate the far field results in the upstream quadrant pointing to JFI near the flaperon trailing edge as the origin of the far field noise changes. Specific sawtooth trailing edges in conjunction with the round nozzle give marginal reduction in JFI noise at approach, and parallel co-rotating mini-vg's are somewhat more beneficial over a wider range of angles, but both concepts are noisier at take-off conditions. These two concepts have generally an adverse JFI effect when used in conjunction with the advanced chevron nozzle at both approach and take-off conditions.