超音速热双喷流斜冲击噪声特征与机理研究

Intensive noise is generated by the exhausts of the aircraft on the carrier impinging on the jet blast deflector. The high level noise is harmful to the personnel on the desk, and may cause structure fatigue of the aircraft. In this project the noise generated by the hot supersonic twin-jet impinging on an oblique plate will be studied with numerical and experimental methods. Four key issues are focused in this study: (1) the noise characteristics and flow structures of the obliquely impinging twin-jet, (2) identifying the noise sources and their locations, (3) the mechanism of the tone noise generated by the oblique impingement of the hot supersonic twin-jet, (4) the influence of the oblique plate downstream on the coupling of the supersonic twin-jet. A high order computational aeroacoustics solver will be used to numerically predict the noise spectra generated by the impinging twin-jet accurately. The block flux reconstruction method developed recently by the present author will be utilized to deal with the complexity of two closely spaced round jets and the oblique plate in the numerical simulation. The unsteady flow and sound fields will be analyzed in detail with dynamic mode decomposition and correlation methods, and a phase analysis will be applied to the key elements of the non-linear feedback loop of impingement tone. The main attention will be focused on the key processes including the generation and development of the large scale flow structures, the interactions between the flow with the shock cells and the oblique plate, and the noise generated by the interactions.

舰载机起飞时尾喷流冲击在挡流板产生的强烈噪声极大地危害舰上工作人员的身心健康，也是飞机结构声疲劳的隐患。本项目拟采用计算气动声学高精度数值模拟与实验测量相结合的方法对高温圆形超音双喷流斜冲击噪声问题进行研究，重点关注四个问题：（1）双喷流斜冲击噪声的流场结构及声场特征；（2）双喷流斜冲击噪声的主要声源类型及其声源位置（3）高温斜冲击情况下纯音出现的机理；（4）下游倾斜平板对双喷流耦合的影响。在数值模拟中将采用申请者发展的网格块界面通量重构方法来解决近距离的圆形双喷管和倾斜平板这种复杂几何问题，以期望能够准确预测双喷流冲击噪声的频谱。本项目将对双喷流斜冲击的非定常流场和声场进行动力学模态分解分析和相关分析，对纯音声反馈环关键要素进行相位分析，研究喷流中大尺度结构产生、发展、与激波和平板相互作用产生声波的整个过程。

舰载机起飞时尾喷流冲击在挡流板产生的强烈噪声，不仅会极大地危害舰上工作人员的身体健康，也是飞机结构声疲劳隐患；而航天火箭发射起飞时高温高热喷流冲击在发射台上产生的高强度噪声,则会危害整流罩内部卫星等精密仪器设备。本项目采用纹影和麦克风等方式对超音速斜冲击喷流噪声进行了实验测量研究，采用计算气动声学高精度方法对超音双喷流斜冲击噪声问题进行了数值模拟研究。通过对比分析单/双自由喷流、单/双冲击喷流的流场结构和声场特征，取得了如下进展：（1）明确了斜冲击双喷流的流场结构及声场特征；（2）得到了平板与喷流距离、平板角度等几何参数对纯音和湍流混合噪声的影响规律；喷流马赫数、温度等流动参数对纯音和湍流混合噪声的影响规律；（3）发现了新的与冲击相关的纯音噪声分量并进行了机理分析；（4）分析了平板对啸音的影响机理；(5)分离出喷流中向上游传播的声波，并明确了其在啸音反馈环中的作用。