Aeroacoustics of jet and cavity flows

工程应用中的许多流动，无论是核反应堆、喷气发动机还是简单的管道系统，本质上都是湍流的，因此会产生压力脉动。一个好的设计，即安全、高效和安静，选择将这些脉动保持在一个可接受的低水平。然而，在涉及声学谐振器的某些情况下，例如连接到阀门的简单管道，流动湍流可以激发强大的声学谐振。例如，当气流的湍流激发了长笛“管”内的声波时，长笛就会发出悦耳的音调。当这些现象在工业应用中出现时，其结果不如长笛的效果好。压力脉动足以产生危险的过度振动，震耳欲聋的噪音水平或导致结构破坏，从而危及工作场所和邻近社区的安全和环境。

Many flows in engineering applications, whether it is a nuclear reactor, a jet engine or a simple piping system, are turbulent in nature and therefore produce pressure pulsations. A good design, that is safe, efficient and quiet, opts to maintain these pulsations at an acceptable low level. However, in some cases involving acoustic resonators, such as a simple pipe connected to a valve, the flow turbulence can excite powerful acoustic resonances. An example would be the pleasant tones of the flute, which are produced when the turbulence of the air stream being blown excites the sound waves inside the flute "pipe". When these phenomena occur in industrial applications, the results are less benign than those of the flute. The pressure pulsations can be sufficiently strong to generate dangerous excessive vibrations, deafening noise levels or cause structural failures and thereby endanger the safety and the environment at the work place and neighboring communities.