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首页> 外文会议>AIAA/CEAS aeroacoustics conference;AIAA aviation forum >Experimental investigation of the acoustic role of the output duct in the discharge of a high pressure flow through diaphragms and perforated plates
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Experimental investigation of the acoustic role of the output duct in the discharge of a high pressure flow through diaphragms and perforated plates

机译：实验研究输出导管在通过隔膜和多孔板排出高压流中的声学作用

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This work presents the second step of an experimental study of the noise radiated by a complete flow discharge/control system allowing to expand or evacuate a flow under pressure by passing though diaphragms or perforated plates. The first step of the study, focused on the study of the noise radiated by the passage of the flow through the perforated plates/diaphragms, allowed to identify the presence of three distinct radiation sources: a broadband noise associated with the mixing of the flow at the exit of the perforations and which is strongly linked to the geometry, a shock noise (screech and broadband shock associated noise) associated with the presence of shock cells in the flow for supersonic regimes and a tonal noise associated with a feedback loop and appearing for low subsonic operating points. By adding a duct downstream to the discharge zone to be closer to real geometries found in industry, the broadband noise is strongly modify by the appearance of strong acoustic resonances in the outlet duct. These resonances are moreover strongly affected by the operating point which drives the flow intensity in the duct. A simple analytical model is proposed in order to quickly predict the different acoustic modifications induced by the outlet duct in case of simple geometries. Finally, the shock noise, as observed without duct, is totally suppressed but is replaced by "base-pressure oscillation" responsible for strong low frequency tones for diaphragms and perforated plates with large cross-sections.
机译：这项工作是对完整的流量排放/控制系统辐射的噪声进行实验研究的第二步，该系统允许通过隔膜或穿孔板在压力下扩展或排空流量。研究的第一步集中在研究流通过多孔板/膜片时所辐射的噪声，从而可以确定三种不同辐射源的存在：与流在此处混合时相关的宽带噪声。穿孔的出口并与几何结构密切相关;对于超声速，与流动中存在冲击单元有关的冲击噪声（与振动和宽带冲击有关的噪声）和与反馈回路相关的音调噪声出现低亚音速工作点。通过在排放区的下游增加一条管道，使其更接近工业中的实际几何形状，出口管道中会出现强烈的声共振，从而大大改变了宽带噪声。此外，这些共振会受到驱动管道中流动强度的工作点的强烈影响。提出了一种简单的分析模型，以便在几何形状简单的情况下，快速预测出气管引起的不同声学变化。最后，在没有导管的情况下观察到的冲击噪声被完全抑制，但被“基本压力振荡”所代替，该“基本压力振荡”对膜片和大横截面的穿孔板产生了强烈的低频音调。

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