Abstract Severe vibrations and sound production can occur in dry gas flow through corrugated pipes. The addition of very small amounts of liquid to the dry gas flow potentially mitigates these flow-induced vibrations (FIVs) and noise. The different mechanisms behind this whistling mitigation are studied in this work, where acoustic measurements are combined with flow visualization and droplet sizing. Different corrugation geometries are studied. It is shown that noise mitigation mainly occurs through a geometric alteration of the cavity mouth, resulting in a reduced acoustic source strength. Additional acoustic damping as a consequence of the presence of droplets has a very limited contribution to the mitigation of FIVs. A non-axisymmetric filling of the cavities of a corrugated pipe with liquid is more effective in reducing the acoustic output, compared to an axisymmetric filling. The liquid viscosity has a minor effect on the achieved noise mitigation. To predict the acoustic source strength for a particular cavity geometry a numerical method is developed, based on URANS simulations combined with Howe's energy corollary. An energy balance method is applied to obtain the acoustic source strength from experiments. The whistling frequencies are accurately predicted with the simulations, but the acoustic source strength is over-predicted by a factor 2. Trends in the source strength obtained from simulations, however, closely resemble the experimentally obtained results. The developed method provides an intuitive understanding of sound production by vortical flow structures and shows potential for the prediction of self-sustained oscillations in corrugated pipes.

中文翻译：

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添加液体使波纹管消音 - 确定减少啸叫的机制

摘要 干气流通过波纹管时会产生剧烈的振动和声音。向干气流中添加非常少量的液体可能会减轻这些流动引起的振动 (FIV) 和噪音。在这项工作中研究了这种啸叫缓解背后的不同机制，其中声学测量与流动可视化和液滴尺寸相结合。研究了不同的波纹几何形状。结果表明，噪声缓解主要通过腔口的几何变化发生，导致声源强度降低。由于液滴的存在而产生的额外声阻尼对减轻 FIV 的贡献非常有限。用液体对波纹管的空腔进行非轴对称填充在降低声输出方面更有效，与轴对称填充相比。液体粘度对实现的降噪效果很小。为了预测特定腔体几何形状的声源强度，开发了一种数值方法，该方法基于 URANS 模拟并结合 Howe 的能量推论。应用能量平衡方法从实验中获得声源强度。通过模拟准确预测了啸叫频率，但声源强度被高估了 2 倍。然而，从模拟中获得的声源强度的趋势与实验获得的结果非常相似。所开发的方法提供了对涡流结构发声的直观理解，并显示了预测波纹管中自持振荡的潜力。