INDUSTRIAL AEROACOUSTICS: PLANAR JETS AND CAVITY FLOWS

工程应用中的许多流动本质上是湍流的，因此会产生压力脉动。安全、高效和安静的流体力学装置的良好设计选择将这些压力脉动维持在可接受的低水平。然而，在涉及流分离和再附着的某些情况下，例如涂漆和涂覆过程中的冲击射流，或建筑穿孔板上的流动，流动湍流可产生强烈的压力脉动。一个例子是长笛的悦耳音调，这是当气流的湍流被吹激发长笛“管道”内的声波时产生的。当类似的现象发生在工业应用中时，所产生的压力脉动比长笛的压力脉动更不温和。它们的强度足以产生危险的过度振动、震耳欲聋的噪音或造成结构故障，从而危及工作场所和邻近社区的安全和环境。即使当所产生的噪声和振动水平足够低并且可以被容忍时，制造产品的表面质量也会由于压力脉动而劣化。

Many flows in engineering applications are turbulent in nature and therefore produce pressure pulsations. A good design of a fluid mechanics device, that is safe, efficient and quiet, opts to maintain these pressure pulsations at an acceptably low level. However, in some cases involving flow separation and reattachment, such as impinging jets in painting and coating processes, or flow over architectural perforated panels, the flow turbulence can generate strong pressure pulsations. 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 similar phenomena occur in industrial applications, the resulting pressure pulsations are less benign than those of the flute. They can be sufficiently strong to generate dangerous excessive vibrations, deafening noise levels or cause structural failures and thereby endanger the safety and the environment of the work place and neighbouring communities. Even when the generated noise and vibration levels are sufficiently low and can be tolerated, the surface quality of the manufactured product can be degraded by the pressure pulsation.