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。一个安全、高效和安静的流体力学设备的好设计，选择将这些压力脉动保持在可接受的低水平。然而，在一些涉及流动分离和再附着的情况下，例如喷漆和涂装过程中的撞击射流，或者在建筑穿孔板上流动，流动湍流可以产生强烈的压力脉动。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。当类似的现象出现在工业应用中时，由此产生的压力脉动不如笛子的压力脉动那么温和。它们的强度可能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故障，从而危及工作场所和邻近社区的安全和环境。即使所产生的噪声和振动水平足够低并且可以容忍，所制造的产品的表面质量也可能因压力脉动而降低。*拟议研究的目的是促进对撞击流产生压力振荡的机制的了解。这项工作将集中在两个通用的流动案例，这是重要的工业应用。在第一种情况下，研究了两个相对的平面射流的振荡，并探讨了这些振荡对镀锌和涂装物体边缘表面质量的影响。更好地了解这些现象将有助于加拿大汽车工业的钢板镀锌工艺。拟议工作的另一项任务是研究建筑行业中使用的穿孔板上流动产生声音(噪音)的原因。这两项研究任务的结果将在设计指南中实施，以避免在设计阶段产生压力脉动，以帮助提高这些通用流动情况的安全性和效率。此外，由于拟议的方案将基础研究与以行业为导向的研究结合在一起，它将成为高素质人员的优秀和有吸引力的培训基地。

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.** **The objective of the proposed research is to advance the state of knowledge of the mechanisms generating pressure oscillations by impinging flows. The work will focus on two generic flow cases which are important for industrial applications. In the first case, the oscillations of two opposing planar jets are investigated and the effect of these oscillations on the surface quality at the edges of galvanized and painted objects is explored. Better understanding of these phenomena will benefit the galvanizing process of sheet steel for the automotive industry in Canada. The other task of the proposed work focuses on the cause of sound (noise) generation by flow over perforated panels used in the architectural industry. The results of both research tasks will be implemented in design guides to avoid the generation of pressure pulsation during the design stage to help improve the safety and the efficiency of these generic flow situations. 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.****