Numerical Study of Mach Number and Thermal Effects on Sound Radiation by a Mixing Layer
Numerical Study of Mach Number and Thermal Effects on Sound Radiation by a Mixing Layer
复制标题
DOI：
10.1260/1475-472x.11.5-6.555
复制
发表时间：
2012-10
影响因子：
1
通讯作者：
C. Moser;E. Lamballais;F. Margnat;V. Fortuné;Yves Gervais
中科院分区：
文献类型：
--
作者：
C. Moser;E. Lamballais;F. Margnat;V. Fortuné;Yves Gervais
研究了马赫数和热效应对二维等温和非等温混合层中声产生和传播机制的影响，马赫数为0.2 ~ 0.4，雷诺数为400。基于特征的配方是用来解决通过直接数值模拟的可压缩Navier-Stokes方程使用高阶格式。辐射声直接计算在一个域中，包括近场气动源区域和远场声传播。在等温混合层中，可以通过与声源的非紧凑性相关联的方向性的增加来识别声场中的马赫数效应。斜压不稳定效应在非等温混合层中可被识别为反向旋转涡度层的存在，由此产生的声源被发现效率较低。声学类比的基础上的分析表明，方向性随马赫数的增加，可以与出现的密度波动的弱振幅，但非常有效的噪声产生在浅的角度。这种影响，结合对流和折射效应，被发现形状的声波波前图案取决于马赫数。
Mach number and thermal effects on the mechanisms of sound generation and propagation are investigated in spatially evolving two-dimensional isothermal and non-isothermal mixing layers at Mach number ranging from 0.2 to 0.4 and Reynolds number of 400. A characteristic-based formulation is used to solve by direct numerical simulation the compressible Navier-Stokes equations using high-order schemes. The radiated sound is directly computed in a domain that includes both the near-field aerodynamic source region and the far-field sound propagation. In the isothermal mixing layer, Mach number effects may be identified in the acoustic field through an increase of the directivity associated with the non-compactness of the acoustic sources. Baroclinic instability effects may be recognized in the non-isothermal mixing layer, as the presence of counter-rotating vorticity layers, the resulting acoustic sources being found less efficient. An analysis based on the acoustic analogy shows that the directivity increase with the Mach number can be associated with the emergence of density fluctuations of weak amplitude but very efficient in terms of noise generation at shallow angle. This influence, combined with convection and refraction effects, is found to shape the acoustic wavefront pattern depending on the Mach number.