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

Abstract

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 outboard flaps, at both approach and take-off conditions using scaled models in a free jet. The flaperon modifications were of two types: sawtooth trailing edge and mini vortex generators (vg's). Parametric variations of these two concepts were 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 corroborated 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 gave marginal reduction in JFI noise at approach, and parallel co-rotating mini-vg's were somewhat more beneficial over a wider range of angles, but both concepts were noisier at take-off conditions. These two concepts had generally an adverse JFI effect when used in conjunction with the advanced chevron nozzle at both approach and take-off conditions. Nomenclature

Experimental and Numerical Investigation of Jet Flap Interaction Effects

“…This phenomenon was revealed in experimental studies [4,5] with a help of far-field microphones array. The region radiated increased high-frequency noise was found near the flap ends.…”

“…In experimental studies [3,4] the region with increased high-frequency noise was found near the flap ends. In these experiments array of phased microphones was used in order to visualize areas with increased noise level.…”

“…Investigations of influence of installation effects on jet noise and flow-field is being conducted during last thirty years [1][2][3][4][5][6][7][8]. The analysis of obtained results is given in [4][5] in detail.…”

On high-frequency sound generated by gust–aerofoil interaction in shear flow

“…This is highly relevant to turbine noise. A second acoustic source connected with aerofoil-flow interaction, which has perhaps received less attention, arises from the airframe at take-off or approach conditions, whereby the deployed wing flaps might interact with the engine exhaust flow to produce noise (Mengle et al 2007;Semiletov et al 2013).…”

Investigation of the effect of a pylon and a wing with flaps on the flow within an exhaust jet of a double-flow turbojet engine by a simulation method for large eddies

“…The consequence of this most often is an increase in the jet noise. Inter action of the wing and flaps with the jet also affects the flow in it [4,5] and causes an increase in the jet noise [6][7][8]. From the aforesaid, investigation of the effect of the pylon and airframe elements on the TJE jet flow becomes practically important.…”