Differentiation of impinging jet noise

High-speed subsonic and supersonic impinging jets are seen in various applications such as cooling of equipment from heavy and large turbine blades, fusion blankets to weightless and micro size electronic chips. Impinging jets are widely used for heating and cooling operations. High rate of exchange of heat, mass and momentum makes these flows very fruitful in many applications. But these flows also contain other features responsible for noise generation, such as high rate of turbulent mixing, boundary layer turbulence and Mach wave radiations at high speeds. In addition to this there are instabilities which are responsible for the production of very painful tones caused by the coupling of fluid flow and acoustic waves. Apart from increase in noise levels if these tones are permitted to interact with surrounding structures, they can cause structural vibration and fatigue failure problems. This article discusses various types of noise in impinging jet and flow physics responsible for it. Acoustic and flow measurement for various impinging jet configuration is carried out. Further flow visualization is performed to show the special noise sources in the flow.