From previous experiments, it was shown that small quantities of liquids reduce or eliminate the singing phenomenon in corrugated tubes. The singing mitigation was attributed to filling up of the corrugations, interference with the boundary layer or due to the increased acoustic damping. To evaluate the influence of the presence of liquids on the acoustic damping, this damping was measured in a smooth and a corrugated tube (internal diameter 49 mm). The damping was measured using an active source (loudspeaker) and measuring amplitude of sound waves on both sides of the pipe. This was done at different gas velocities (U = 0, 15, 30 m/s) and different liquid injection rates (0, 150, 250 350 ml/min) for a frequency range between 0-2200 Hz. The smooth pipe results compared well with literature models such as the Kirchhoff model. In the presence of liquid, the acoustic damping increased linearly with the liquid rate. This increase was higher than expected based on the assumptions of mist flow or overall pressure drop. In case of the corrugated tube, the measured damping is dominated by a large fluctuation due to the source behavior (negative damping) at flowing conditions. At low velocities a decrease in source strength was measured with increasing liquid. At higher gas velocities, it was observed that liquid has almost no effect on the damping.
展开▼
机译：从以前的实验中可以看出，少量液体减少或消除了波纹管中的鸣叫现象。减轻歌唱归因于波纹的填充，对边界层的干扰或由于增加的声阻尼。为了评估液体的存在对声阻尼的影响，在光滑的波纹管（内径49 mm）中测量了该阻尼。使用有源源（扬声器）测量阻尼，并测量管道两侧的声波幅度。对于0-2200 Hz之间的频率范围，这是在不同的气体速度（U = 0、15、30 m / s）和不同的液体注入速率（0、150、250 350 ml / min）下完成的。光滑管道的结果与Kirchhoff模型等文献模型进行了很好的比较。在液体存在的情况下，声阻尼随液体流速线性增加。根据雾流或总压降的假设，该增加量高于预期。对于波纹管，由于在流动条件下的源行为（负阻尼），所测得的阻尼主要受较大波动的影响。在低速下，随着液体的增加，测量到的源强度下降。在较高的气体速度下，观察到液体几乎对阻尼没有影响。
展开▼
