The flow-excited acoustic resonance phenomenon is created when the flow instability oscillations are coupled with one of the acoustic modes, which in turn generates acute noise problems and/or excessive vibrations. In this study, the effect of the upstream edge geometry on attenuating these undesirable effects is investigated experimentally for flows over shallow rectangular cavity with two different aspect ratios of L/D = 1 and 1.67, where L is the cavity length and D is the cavity depth, and for Mach number less than 0.5. The acoustic resonance modes of the cavity are self-excited. Twenty four different upstream cavity edges are investigated in this study; including round edges, chamfered edges, vortex generators and spoilers with different sizes and configurations. The acoustic pressure is measured with a flush-mounted microphone on the cavity floor and the velocity fluctuation of the separated shear layer before the onset of acoustic resonance is measured with a hot-wire probe. The results for each upstream cavity edge are compared with the base case when square cavity edge is used. It is observed that when chamfered edges are used, the amplitude of the first acoustic resonance mode is highly intensified with values reaching around 5000 Pa (compared to 2000 Pa for the base case) and a clear shift in its onset of resonance to higher flow velocities is observed. Similar trend is observed when round edges are used. The amplitude of the generated pressure of the first acoustic resonance mode is amplified with values exceeding 4000 Pa and a delay in its onset of acoustic resonance is observed as well. Most of the spoiler edges are found to be effective in suppressing the pressure amplitude of the excited acoustic resonance. However, the performance of each spoiler depends on its specific geometry (i.e. thickness, height, and angle) relative to the cavity aspect ratio. A summary of the results is presented in this paper.
展开▼
机译：当流量不稳定性振荡与其中一个声学模式耦合时，产生流动激发的声学谐振现象，这又产生急性噪声问题和/或过度振动。在该研究中，实验研究上游边缘几何形状对衰减这些不期望的效果的影响，以在浅矩形腔中流动，其中L / D = 1和1.67的两个不同的纵横比，其中L是腔长，D是腔体深度，机器数小于0.5。腔的声谐振模式是自我激发的。在本研究中研究了二十四个不同的上游腔边缘;包括圆形边缘，倒角边缘，涡流发生器和具有不同尺寸和配置的扰流器。在腔底上用嵌合的麦克风测量声压，并且在用热线探针测量声谐振开始之前分离的剪切层的速度波动。当使用方腔边缘时，将每个上游腔边缘的结果与基础壳体进行比较。观察到，当使用倒角边缘时，第一声谐振模式的幅度高度加强，其值达到约5000Pa（与基本情况的2000Pa相比），并且其在其谐振开始到更高的流速的透明移位观察到。使用圆形边缘时观察到类似的趋势。第一声谐振模式的产生压力的幅度被超出4000Pa的值放大，并且也观察到其声谐振开始的延迟。发现大多数扰流器边缘有效地抑制激发声学共振的压力幅度。然而，每个扰流板的性能取决于相对于腔纵横比的特定几何形状（即厚度，高度和角度）。本文提出了结果的摘要。
展开▼
