机翼表面脉动压力的空间和频域特性数值研究

Numerical Study of Pressure Fluctuation Spatial and Frequency Domain Characteristics on Airfoil Surface

机翼表面脉动压力是大型客机近场噪声的主要来源之一,对其空间和频域分布特性开展研究有重要意义.采用大涡模拟方法对弦长1 m、后掠角45°的无限翼展NLF(2)-0415机翼的绕流场在Re_(C)=2.42×10^(6)的条件下开展了数值研究,分析了不同湍流来流条件及不同流动状态对机翼上表面时均流场及脉动压力声压级和功率谱的影响.计算结果表明:在本文条件下,机翼上表面脉动压力在转捩位置处有明显突增,湍流区声压级比层流区高出约20~30 dB;来流湍流强度对壁面脉动压力的影响主要集中在层流区,湍流区的壁面脉动压力对来流湍流强度变化反应不敏感;层流区脉动压力功率谱整体较低,且随频率的增加衰减较快,而湍流区脉动压力功率谱相比层流区在全频段均提升了约2~3个数量级,且谱级在低频段随频率的变化较小,在高频段则随频率增加以一定斜率下降.

The wing surface pressure fluctuation is one of the main sources of large passenger aircraft near-field noise,and the study of its spatial and frequency domain distribution characteristics is of great significance.The large eddy simulation method were used to carry out Re_(C)=2.42×10^(6)numerical calculation research for an infinite wingspan NLF(2)-0415 airfoil with a chord length of 1 m and a sweep angle of 45 degrees.The effects of different turbulent incoming flow conditions and flow states on the time-averaged flow field and pressure fluctuation sound pressure level and power spectrum on the upper surface of the wing were analyzed.The research results show that under the conditions of this paper,the pressure fluctuation on the upper surface of the wing has an obvious sudden increase at the transition position;the sound pressure level in the turbulent flow zone is about 20~30 dB higher than that in the laminar flow zone;the influence of the incoming turbulence intensity on the surface pressure fluctuation is mainly concentrated in the laminar flow zone,and the pressure fluctuation in the turbulent zone is not sensitive to the incoming turbulence intensity;the pressure fluctuation power spectrum in the laminar flow zone is generally low,and decreases fast as the frequency increases;the pressure fluctuation power spectrum in the turbulent flow zone is increased by about 2~3 orders of magnitude in the whole frequency band compared with the laminar flow zone,and the spectrum level changes little with frequency in the low frequency range,and decreases with a certain slope as the frequency increases in the high frequency range.