Numerical simulation of jet mixing noise associated with engine exhausts

本项目涉及发动机排气噪声的数值预测。这个主题特别有趣，因为它涉及许多不同的流动特征，冷和热射流湍流的混合，自由剪切层和壁面有界流动。因此，为了获得亚音速射流中声源及其近场的准确估计，必须在CFD代码中进行特殊的数值开发。将与项目的其他CFD合作伙伴一起研究和验证几种数值方法。同时，还将讨论非定常壁面流动计算的物理相关性及其在声学远场估计中的适用性。为此目的，将使用法国合作伙伴提供的实验基准。这个基准结合了湍流射流与准周期性扰动的圆形圆柱冲击在下游定位翼型。因此，在实验上解决了紊流射流附近的壁面有界流动问题。这个实验的大部分结果已经得到了，但还需要进行一些额外的测量。本文将对非定常流场和声远场进行比较。远场计算将通过将瞬时源项整合到ffwoocs - williams - hawkins类比的高级时间公式中来实现。

This project is concerned with the numerical prediction of engine exhaust noise. This topic is of particular interest because it involves many different flow features, mixing of cold and hot jet turbulent flows, free shear layers and wall bounded flows. Therefore, special numerical developments will have to be achieved in the CFD codes in order to obtain accurate estimates of the acoustic sources and their near field in subsonic jets. Several numerical approaches will be investigated and validated with other CFD partners of the project. In parallel the difficult question about the physical relevance of unsteady wall flow computations and their applicability to acoustic far field estimates will be addressed. For that purpose, an experimental benchmark from the French partner will be used. This benchmark combines a turbulent jet flow with the quasi periodic disturbance of a circular cylinder impinging on a downstream located airfoil. Thus, the problem of a wall bounded flow in the vicinity of a turbulent jet flow is addressed experimentally. Most results of this experiment are already available, but a few additional measurements will be carried out. Comparisons will be made both on the unsteady flow field and on the acoustic far field. Far field computations will be achieved by integrating the instantaneous sources terms into an advanced time formulation of the Ffwocs-Williams-Hawkings analogy.