INDUSTRIAL AEROACOUSTICS: PLANAR JETS AND CAVITY FLOWS

点击翻译按钮获取中文摘要

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.