Aero-acoustic analysis and assessment of conceptual low-noise airframe configurations
Konferensbidrag (offentliggjort, men ej förlagsutgivet), 2015
High-lift (HL) configuration represents a significant part of airframe noise. Two different low-noise HL designs have been assessed with respect to a baseline HL configuration, which is a full-scale regional aircraft wing with a double-slotted part-span flap. The first design uses a single slotted flap. The second design, with a single slotted flap, has invoked a Krueger flap. Hybrid CFD/CAA analysis has been performed using acoustic analogies (the Kirchhoff, FW-H and Curle methods) based on hybrid RANS/-LES computations. It is shown that the Krueger flap has the best aerodynamic and aero-acoustic performances, which haves led to a noise reduction by 6-10dB. One of energetic airframe noise sources is associated to turbulent flow motion over the flap side-edge (FSE). To reduce FSE noise, a fence is attached onto the side edge. In the analysis of this configuration, an effective stochastic noise generation and radiation (SNGR) method was used, which formulates the noise sources based on the RANS solutions computations. The Lighthill acoustic analogy and boundary element method (BEM) in frequency domain have been employed for noise prediction. The analysis shows that the fence is able to effectively reduce noise by about 7dB. Another dominant airframe noise source is the turbulent flow induced by a landing gear (LG). Four low-noise conceptual designs are investigated for a full-scale main landing gear (MLG). The LG-bay door is opened to explore its noise scattering effect. Several different concepts measures for noise reduction have been investigated, including fairing, shallow LG-bay and acoustic liners. The aero-acoustic analysis has been demonstrated that, with a lined bay rear wall, the noise level has been was reduced by 1.817dBA. In the presentation, the aero-acoustic analysis and assessment on the aforementioned airframe configurations will be reporteds and discussed.