Shock-induced noise in supersonic jets

具有复杂激波结构的超音速射流产生高强度的宽带和小频带噪声(尖叫声)，导致结构疲劳和强烈的环境噪声污染。虽然尖叫声的频率在理论上是可以预测的，但到目前为止，它们的幅度还不能准确计算。该项目的目的是可靠地预测这样的噪声水平，并有助于更好地理解冲击波引起的噪声产生和传播的基本物理学。慕尼黑理工学院(TUM)和里昂中央学院(ECL)提供的两种不同的高精度可压缩Navier-Stokes解算器将用于直接对超音速完全膨胀和过度膨胀圆形射流进行数值和大涡模拟。ECL的团队将专注于LES，而TUM的团队将使用DNS进行流量和噪声预测。将定义一种常见的低雷诺数流动情况，它允许比较大涡模拟和直接模拟的噪声预测。详细的超音速喷流数据是基于线性化欧拉方程进行噪声传播研究的输入。该项目在下一个三年阶段的目标将与通过修改喷嘴嘴唇的形状来控制冲击噪声有关。

Supersonic jets with complex shock-cell structures produce broadband and smallband noise (screech tones) of high intensity which contributes to structural fatigue and to strong environmental noise pollution. While the screech frequencies are theoretically predictable, their amplitudes cannot, until now, be computed precisely. It is the aim of this project to predict such noise levels reliably and to contribute to a better understanding of the fundamental physics of shock-induced noise generation and propagation. Two different highly accurate compressible Navier-Stokes solvers, available at TU Munich (TUM) and École Centrale de Lyon (ECL) will be used to perforin direct numerical and large-eddy simulations of supersonic perfectly expanded and overexpanded round jets. While the group at ECL will concentrate on LES, the group at TUM will use DNS for flow and noise prediction. One common low Reynolds number flow-case will be defined which allows to compare noise predictions by LES and DNS. Detailed supersonic jet data are the input for noise propagation studies based on the linearized Euler equations. The goal of the project during the next 3-year phase will be related to the control of shockinduced noise by shape modifications of the nozzle lip.