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可接受的低水平。然而，在一些涉及声学谐振器的情况下，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共振。一个例子是笛子的悦耳音调，当吹来的气流的湍流激发笛子“管子”内的声波时，就会产生悦耳的音调。当这些现象在工业应用中出现时，结果不如长笛的结果好。压力脉动可能足够强，从而产生危险的过度振动、震耳欲聋的噪音水平或导致结构故障，从而危及工作场所和邻近社区的安全和环境。 拟议研究的目的是提高对这些现象的认识状态，以及流动激励的声学共振发生的条件。研究工作将集中于在许多工业应用中经常遇到的三种通用流动情况，如燃气和蒸汽管道系统、核电站和常规电站、喷气发动机、钢铁制造和许多航空应用。这些结果将被用于制定设计指南，以帮助提高这些应用程序的安全性和效率。此外，由于拟议的计划将基础研究与以行业为导向的研究相结合，它将为高素质人员提供一个极好和有吸引力的培训基地。

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. The objective of the proposed research is to advance the state of knowledge of these phenomena and the conditions under which flow-excited acoustic resonances occur. The research work will focus on three generic flow cases which are often encountered in many industrial applications such as gas and steam piping systems, nuclear and conventional power stations, jet engines, steal manufacturing and many aeronautical applications. The results will be used to develop design guidelines to help improve the safety and the efficiency of these applications. Furthermore, since the proposed program combines fundamental investigations with industry-oriented research, it will constitute an excellent and attractive training ground for highly qualified personnel.