Airframe noise studies on wings with deployed high-lift devices

Slat Cove Unsteadiness: Effect of 3D Flow Structures

“…The lower Reynolds number in the BART experiments reflects an essential compromise of the type mentioned at the beginning of this section. A likely aeroacoustic artifact of low Reynolds number high-lift configurations corresponds to prominent narrowband peaks in both nearfield and farfield frequency spectra [3,30]; some of these peaks have been attributed to Rossiter modes of the open cavity flow in the slat cove region. 30 However, no evidence of narrowband peaks (other than the peak associated with vortex shedding from the slat trailing edge) was found during the present simulations for the BART configuration.…”

“…The ranking of these sources is configuration dependent; typically, noise due to high-lift system dominates for the medium sized aircraft, whereas landing gear noise could be more important for the larger twin-engine transports. Model scale tests [1][2][3][4][5][6] have identified the leading-edge slat as a prominent source of airframe noise during approach conditions. These findings are corroborated by the flyover noise measurements for the Airbus A340 7 .…”

Effects of Geometric Details on Slat Noise Generation and Propagation

“…Minimizing the noise on approach is important for the quality of life of residents living near airports and allow for increased airport capacity. Among the various high-lift components, the leading-edge slat and the side edges of the flaps have been identified as prominent airframe noise sources [1][2][3][4] . For practical reasons, mostly model scale experiments have been relied upon to provide insight on sound generation and the radiated acoustic field 3,[5][6][7] .…”

“…Experimental and computational studies, focused on leading-edge slats, have been instrumental in providing the foundation for an in-depth understanding of noise generation mechanisms and the radiated sound field 3,6,7,[9][10][11][12][13][14][15][16][17][18] . Following Dobrzynski et al 3 , compilation of past acoustic measurements 3,6,7,9,10 reveals a near universal Strouhal (St) scaling, based on the slat chord C s and freestream velocity, for the frequency spectrum.…”

Method of Analyzing the Wind Tunnel Test Data Measured with Directional Microphone Systems

“…Here the noise source has to fulfill the following requirements. We used a speaker noise for frequencies below the 3.15 kHz band and a jet noise for frequencies above the 4 kHz band, both of which were embedded in a smooth shaped supporting structure to reduce the aerodynamic noise originated by the source body itself 3) . These noise sources almost satisfy these conditions at frequencies from 1 kHz to 20 kHz though the condition (b) is not satisfied at lower frequencies and the conditions (a) and (c) are not satisfied at higher frequencies.…”