INDUSTRIAL AEROACOUSTICS: PLANAR JETS AND CAVITY FLOWS

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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.