高超声速风洞中来流扰动模态特征的研究

It is well known that the freestream disturbance of wind tunnel has a direct impact on hypersonic boundary-layer transition. In order to obtain a quantitative assessment of such process, the disturbance modes of the hypersonic wind tunnel must be qualified at the first step. A novel methodology using Constant Temperature Anemometer and focused laser differential interferometer simultaneously and its respective post-processing method are developed to systematically investigate the disturbance modes of the hypersonic freestream. Firstly, the hypersonic disturbance modal decomposition based on the raw experimental data is discussed for the independent, partial-correlated and sound-wave dominated cases respectively, and the disturbance modal decomposition suitable for conventional hypersonic wind tunnel is devised; thereafter, the evolution characteristics of vorticity and modes entropy along the Laval nozzle, such as frequency and amplitude, are studied by introducing artificial perturbations ahead of the Laval nozzle, and the heat equation of these two modes are established; additionally, eddy Mach wave and shivering Mach wave have been quantitatively investigated using a two-channel Constant Temperature Anemometer system, and the contributions of these two sub-modes to the sound-wave mode have been also qualified. This research reveals the detailed characteristics of the vorticity, entropy and sound-wave modes in hypersonic wind tunnels. The content of the framework is critical for the experimental research of laminar/turbulent boundary-layer transition in hypersonic flow, as well as the development of large hypersonic wind quiet tunnels.

高超声速风洞的来流扰动对边界层转捩有直接影响，定量评估该过程需要对来流扰动模态进行全面的特征分析。本项目提出了恒温热线仪/聚焦激光差分干涉仪联合测量来流扰动模态的新方法，并通过对测量数据后处理，重点研究高超声速风洞中来流扰动模态的特征。通过系统测量高超声速风洞自由来流的脉动参数，研究基于来流脉动参数的扰动模态分解方法，揭示互不相关、部分相关和声波占优模态下的流场脉动特征和物理机理，建立常规高超声速风洞来流扰动模态分解准则；引入人工小扰动，研究涡波和熵波模态经过高超声速Laval喷管加速后幅值和频率的变化规律，建立对应的热力方程模型；实验研究声波扰动子模态（涡流马赫波和颤振马赫波）行为特征，探明涡流和颤振马赫波对声波模态的贡献。该研究旨在揭示涡波、熵波和声波扰动子模态在高超声速风洞中的发展过程和演变规律，项目的开展将为高超声速层/湍流边界层转捩研究以及发展我国大型高超声速静风洞提供理论依据。

高超声速风洞的来流扰动对边界层转捩有直接影响，定量评估该过程需要对来流扰动模态进行全面的特征分析。本项目搭建了聚焦激光差分干涉仪测试技术，结合热线风速仪、皮托探头开展了马赫6高超声速风洞来流扰动模态测量与解耦分析，获得了高超声速风洞中涡波、熵波和声波幅值，为下一步开展高超声速边界层转捩的感受性等问题研究提供了支撑；其次，开展了高超声速湍流噪声辐射研究，通过高精度数值模拟方法，确定了高超声速流动情况的噪声辐射主要来源雷诺应力的二阶脉动项，并初步确定了高超声速湍流边界层下壁面压力脉动与自由来流中压力脉动的比值关系，基于以上工作开展了高超声速风洞湍流壁面噪声辐射控制研究，并获得初步的成果。以上研究部分成果已经在国内相关研究单位得到了应用。