襟翼侧缘噪声机理及修型降噪设计

Noise reduction design and analysis on flap side-edge shape modification

襟翼侧缘噪声是飞机起降阶段机体噪声的重要噪声源。采用极大涡模拟对襟翼侧缘非定常流场进行数值模拟,分析其噪声产生机理.基于此,提出了两种襟翼侧缘修型方式,应用虚拟渗透面的Ffowcs Williams and Hawkings(FW-H)声比拟方法将修型构型的远场噪声频谱特性和指向性与基准构型对比分析,研究其降噪效果。通过流场和声场的数值模拟表明,襟翼侧缘噪声属于宽频噪声。不同的襟翼侧缘形状改变了流场形态、侧缘涡结构以及涡系的发展过程,进而对声源分布和远场噪声特性产生影响。结果表明:在给定的5°计算迎角下,两种襟翼侧缘修型方式在保证增升装置的原有升阻气动特性的前提下,能达到减小全场总声压级1~2 dB的降噪效果。

Flap side-edge noise is a significant noise source for airplane at takeoff and landing stages.The noise generation mechanism from flap side-edge noise is analyzed by numerical simulation of unsteady flow field using Very Large Eddy Simulation(VLES).Two kinds of flap side-edge shape modifications are proposed on the basis,and their frequency spectrum and directivity of far-field noise are compared with the baseline configuration using permeable integral surface Ffowcs Williams and Hawkings(FW-H)acoustic analogy method to investigate their effects on noise reduction.Via the numerical simulation of flow field and acoustic field,it proves that the flap side-edge noise is broadband noise in nature.The different shapes of flap side-edge change the pattern of flow field,vortex structures and the developing process of vortex,thus having influences on noise source distributions and characteristics of far-field noise.The result shows that at the given 5°angle of attack,the proposed flap side-edge shape modifications can achieve reduction of the overall sound pressure level(OASPL)ranging from 1 to 2 dB without decreasing the lift and drag aerodynamic performances too mach.