Analysis of Different Sound Source Formulations to Simulate Combustion Generated Noise Using a Hybrid LES/APE-RF Method
Analysis of Different Sound Source Formulations to Simulate Combustion Generated Noise Using a Hybrid LES/APE-RF Method
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使用混合 LES/APE-RF 方法分析不同声源配方以模拟燃烧产生的噪声
DOI：
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发表时间：
2009
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通讯作者：
H. Pitsch
中科院分区：
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作者：
T. Bui;M. Ihme;W. Schröder;H. Pitsch
研究了DLR-A火焰的燃烧噪声和声源机理。采用大涡模拟/计算气动声学(LES/CAA)混合方法。在混合分析的第一步中，采用火焰面/进度变量(FPV)模型作为燃烧模型，然后在第二步中使用反应流动的声学摄动方程(APE-RF)进行声学模拟。已在声源术语方面扩展了小火焰/进度变量数据库。对热声源(如非定常热释放)引起的低马赫数反应流声场的分析导致了一个非常僵硬的问题，因为相关的源需要在源区内有高分辨率的区域，这限制了可能的时间步长。要使用这种混合方法模拟燃烧产生的噪声，必须使用合适的源描述，该描述最好满足两个要求，即高效和准确地预测产生的声场，而源项可以很容易地从LES中估计出来。使用由密度的比例偏时间导数表示的源项，声场可以在最大Strouhal数STD=2的情况下得到最好的再现。然而，这种源公式要求在混合方法的界面处有严格的约束，以避免由内插引起的人为加速引起的杂散噪声。更准确地说，密度不均匀的对流速度必须在内插过程中保持不变。使用通过密度的定标材料导数表示的源公式可以实现效率和精度之间的折衷，因为从定义上讲，该公式不描述密度不均匀的对流。
Combustion noise and sound source mechanisms of the DLR-A flame are investigated. A hybrid large-eddy simulation/computational aeracoustics (LES/CAA) approach is employed. In the first step of the hybrid analysis the flamelet/progress variable (FPV) model is employed as combustion model followed by the acoustic simulation in the second step using the acoustic perturbation equations for reacting flows (APE-RF). The flamelet/progress variable database has been extended in terms of acoustic source terms. The analysis of the acoustic field of low MACH number reacting flows induced by the thermoacoustic sources such as the unsteady heat release leads to a very stiff problem formulation, since the related sources require highly resolved regions in the source area, which restricts the possible time step. To simulate combustion generated noise using such a hybrid approach, a suitable source description has to be used, which preferably satisfies two requirements, i.e, to efficiently and accurately predict the generated sound field, while the source term can be easily evaluated from the LES. Using the source term, which is expressed via the scaled partial time derivative of the density, the acoustic field can be reproduced best up to a maximum Strouhal number of StD = 2. However, this source formulation requires a rigorous constraint at the interface of the hybrid approach to avoid spurious noise due to artificial acceleration caused by interpolation. To be more precise, the convection speed of density inhomogeneities has to be preserved during interpolation. A compromise between efficiency and accuracy can be achieved using the source formulation expressed via the scaled material derivative of the density, since by definition this formulation does not describe the convection of density inhomogeneities.