非线性扰动方程研究平面混合层发声机制

发布时间：2018-05-14 04:32

本文选题：非线性扰动方程 + 超声速混合层　；参考：《空气动力学学报》2016年05期

【摘要】：在流动过程中由脉动引起的噪声问题在自然界和工业界中广泛存在,研究流动过程中不稳定波的发声机制对于理解、预测并最终控制气动噪声有着重要意义。本文以二维Blasius相似性解作为基本流场,以超声速混合层作为研究对象,采用非线性扰动方程(NLDE)研究超声速混合层不稳定波的近场动力学特性与远场声辐射之间的内在联系。针对不同类型的对流马赫数,分别研究对流马赫数Mc=0.5(1)和Mc=1.2(≥1)两种情况下的扰动发声机制,结果表明:当对流马赫数Mc1时,流场中的发声机制主要由大尺度结构的涡条发声,且基本波与亚谐波之间的非线性作用能增强辐射强度;当对流马赫数Mc≥1时,根据扰动相速度是相对于上层还是下层自由流速度为超声速,可以进一步分为快慢两种模态,分别对快慢两种模态以及其相互作用模态进行了数值模拟研究,计算得到流场中的发声机制是以马赫波形式辐射向远场,即马赫波辐射,其辐角的计算结果与理论值相符。
[Abstract]:The noise problem caused by pulsation in the flow process exists widely in nature and industry. The study of the sound mechanism of unstable waves in the flow process is of great significance for understanding, predicting and controlling aerodynamic noise. In this paper, the two-dimensional Blasius similarity solution is used as the basic flow field, and the supersonic mixing layer is taken as the research object. A nonlinear perturbation equation (NLDE) is used to study the intrinsic relationship between the near-field dynamic characteristics of the unsteady wave of supersonic mixing layer and the sound radiation from the far field. According to the different types of convective Maher numbers, we study the disturbing sound mechanism of the convective Maher number (1) and Mc=1.2 (> 1) respectively. The results show that when the convective Maher number is Mc1, the flow field is in the flow field. The sound mechanism in the medium is mainly composed of a large scale vortex bar, and the nonlinear action between the basic and subharmonic waves can enhance the radiation intensity. When the convective Maher number Mc is more than 1, the velocity of the disturbance phase is relative to the upper or lower flow velocity of the supersonic velocity. It can be divided into two modes, which are two modes of fast and slow speed, respectively. The numerical simulation of the state and its interaction mode is carried out. The sound mechanism in the flow field is calculated to radiate to the far field in the form of Maher wave, that is, Maher wave radiation. The calculation results of the radiant angle are in agreement with the theoretical values.

【作者单位】：天津大学机械工程学院力学系;
【基金】：国家自然科学基金(11332007,10972156)
【分类号】：O302;V211

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