Abstract Entropy noise is produced when temperature fluctuations (entropy spots) are accelerated by the mean flow, through a nozzle or a turbine stage for instance. When it propagates outside the engine it contributes to community noise and may generate thermoacoustic instabilities when reflected back towards the combustor, hence the need for its modelling. Among all the inviscid models proposed in the literature, only the one developed by ONERA takes into account the 2D nature of the mean flow and the radial deformation of the entropy waves through the nozzle, which plays a crucial role in noise generation (Emmanuelli et al., J. Sound Vib., vol. 472, 2020, pp. 115163). This model has been validated in the subsonic regime and is extended in the present work to 2D supercritical configurations, without and with a normal shock in the diffuser. Modelled transfer functions are validated by comparison with reference data obtained with computational aeroacoustics simulations and excellent agreement is found between the simulations and the model. The contribution of the shear dispersion of the entropy wave to noise generation is evidenced and the failure of the quasi-1D models, which do not account for the radial deformation of the entropy fluctuations, is illustrated. Noise scattering through the nozzle is also investigated. The 2D model is found to correctly recover the simulated transmitted and reflected acoustic waves through the nozzle. Quasi-1D solutions are also found to collapse with the reference simulations, which indicates that 2D mean flow effects are negligible for the propagation of the acoustic waves through the nozzle.

中文翻译：

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二维阻塞喷嘴流中的熵噪声建模

摘要 当温度波动（熵点）被平均流加速时，例如通过喷嘴或涡轮级，就会产生熵噪声。当它在发动机外传播时，它会产生社区噪声，并且在反射回燃烧器时可能会产生热声不稳定性，因此需要对其进行建模。在文献中提出的所有无粘性模型中，只有 ONERA 开发的模型考虑了平均流的二维性质和通过喷嘴的熵波的径向变形，这在噪声生成中起着至关重要的作用（Emmanuelli et al ., J. Sound Vib.，第 472 卷，2020 年，第 115163 页）。该模型已在亚音速状态下得到验证，并在目前的工作中扩展到 2D 超临界配置，扩散器中没有和有正常冲击。通过与计算气动声学仿真获得的参考数据进行比较来验证建模的传递函数，并且在仿真和模型之间发现了极好的一致性。熵波的剪切色散对噪声生成的贡献得到了证明，并说明了准一维模型的失败，该模型没有考虑熵波动的径向变形。还研究了通过喷嘴的噪声散射。发现 2D 模型可以正确恢复通过喷嘴的模拟传输和反射声波。还发现准一维解在参考模拟中崩溃，这表明二维平均流效应对于通过喷嘴的声波传播可以忽略不计。