飞机起落架气动噪声特性仿真与试验

 对某型飞机前起落架的气动噪声特性进行了数值仿真分析和声学风洞试验研究。在典型飞机着陆速度下,采用分离涡(DES)方法模拟起落架周围非定常湍流流场,通过涡声理论计算声源的强度和位置,并利用FW-H(Ffowcs-Williams/Hawkings)方程积分外推法求解出不同部件及其组合件产生的声场,分析其噪声的产生机制、频谱特性及远场指向特性,同时评估各部件对总噪声的贡献量。在声学风洞中对轮胎和轮叉组合件进行气动声学试验,借助麦克风测量获得了噪声的频谱特性。基于部件固体表面积分计算的仿真结果与试验结果在声学远场条件下吻合较好。仿真结果表明:起落架气动噪声是钝体绕流噪声和空腔噪声的叠加,呈现宽频噪声的特性。强度最大的声源主要分布在起落架各部件的固体表面;轮胎噪声对总噪声的贡献最大,其次是轮叉噪声,支柱噪声对总噪声贡献最小。各部件噪声和总噪声均具有偶极子声源的辐射特性。空间可穿透积分面计算的声压级结果比固体表面计算的声压级结果大5 dB左右。该研究结果为低噪声起落架设计提供了一定的参考。

Simulation and Experiment on Aeroacoustic Noise Characteristics of Aircraft Landing Gear

Simulation analysis and experimental research are performed on the aeroacoustic noise characteristics of an aircraft nose landing gear in this paper.At the flight speed during the approach phase,the flow field of an aircraft nose landing gear is produced by means of detached eddy simulation(DES).The source strength and location are determined though the vortex sound theory.Meanwhile,the acoustic field radiated from different model parts or assembled parts are calculated via FW-H(Flowcs-Williams/Hawkings) equation.The noise mechanism,frequency spectra and the directivity characteristics are subsequently studied,and the contribution of each part is assessed.The acoustic field radiated from the assembled parts of the wheel and bogie is measured in an aeroacoustic wind tunnel.The noise spectra are evaluated by microphones.A comparison shows that the simulation results agree well with the experiment results under the acoustic far field condition.The results indicate that the landing gear noise is broadband noise,which is mainly generated by flow separation off the bluff body and superimposed by tonal noise.The sources with the biggest strength are on the solid surface of each part.The wheel is the largest contributor and the strut is the least contributor to the landing gear noise.The noise radiation directivities of each part and the whole model are similar in possessing dipole characteristics.The sound pressure level calculated from the porous surface is about 5 dB greater than that calculated from the solid surface.The results can provide some reference for low noise landing gear design.