超音速圆形双喷流耦合机理研究

Two parallel supersonic jets with closely center-to-center spacing exhibit resonant oscillations and generate high intensity dynamic pressure in the inter-nozzle region which may cause fatigue of aircraft structures. In this project the coupling mechanism of twin supersonic round jets will be studied with numerical and experimental methods. A high order computational aeroacoustics solver will be used to numerically predict the frequency and amplitude of the resonant oscillations generated by the coupling twin-jet accurately. The block flux reconstruction method developed recently by th present author will be utilized to deal with the complexity of two closely spaced round jets in the numerical simulation. The unsteady flow and sound fields will be analyzed in detail with POD and correlation methods, and a phase analysis will be applied to the key elements of the non-linear feedback loop. The main attention will be focused on the key processes including the generation and development of instabilities, the interaction between instabilities and the shock cells, the feedback acoustic waves. The relationship of the feedback loops between the twin-jet coupling resonance and the original screech tone will be analyzed. The source of screech tones will be localized, and a new formula for the prediction of the frequency of the twin-jet resonance will be constructed.

超音速双喷流耦合会在喷管间区域产生高强度的动态压力负载从而引起结构声疲劳。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圆形超音双喷流耦合现象进行研究。在数值模拟中将采用申请者最近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这种复杂几何问题，以期望能够准确预测双喷流耦合振荡产生的啸音频率和幅值。本项目将对双喷流非定常流场和声场进行POD分析和相关分析，对声反馈环关键要素进行相位分析，研究喷流中大尺度不稳定波产生、发展、与激波相互作用产生声波并反馈到喷管唇口的整个过程，分析双喷流耦合反馈环的关键要素及其与原有啸音模态反馈环间的关系；确定耦合振荡发声的声源位置，发展耦合振荡频率预测公式。

超音速双喷流耦合会在喷管间区域产生高强度的动态压力负载从而引起结构声疲劳。本项目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圆形超音双喷流耦合现象进行了研究。本项目对马赫数范围1.05—1.6的超音速双喷流及同等工况的单喷流开展了实验测量，研究了马赫数、喷管间距、下游挡流板等因素对双喷流耦合噪声的影响；在数值模拟方面，本项目改进并推广了网格块界面通量重构方法，在保证高阶差分格式精度的同时，提高了其处理复杂几何能力，同时发展了基于SA模型的脱体涡湍流模拟方法和多时间步长推进方法，为双喷流噪声的精确模拟打下基础；采用所发展的高精度数值方法对马赫数范围1.05—1.6超音速双喷流及同等工况下的单喷流进行了数值模拟，准确预测了双喷流耦合振荡产生的啸音频率和幅值，研究了马赫数、喷管间距、温度及下游挡流板对双喷流耦合噪声的影响；对单、双喷流非定常流场和声场进行动力学模态分解分析，对声反馈环关键要素进行相位分析，明确了喷流中大尺度不稳定波模态与啸音模态的关系，确定了耦合振荡发声的声源位置及其与单喷流的区别，解释了耦合振荡增强啸音及其谐波模态幅值的原因；发展了耦合振荡频率预测公式，并依据此公式和双喷流耦合机理，解释了双喷流啸音频率偏移的现象。