Low frequency sound generated by flow separation in a conical diffuser |
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| Institution: | 1. PLADEMA-CONICET, Universidad Nacional del Centro de la Provincia de Buenos Aires, Tandil, Argentina;2. Universitat Pompeu Fabra, Barcelona, Spain;3. Medisys, Philips Research, Paris, France;4. Neurochirurgie, Département de Neurosciences Cliniques, Faculté de Médecine, Université de Genéve, Genéve, Switzerland;5. Hirslanden Clinic, Zürich, Switzerland;1. School of Remote Sensing and Information Engineering, Wuhan University, Wuhan 430079, China;2. Key Laboratory of Digital Earth Science, Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, Beijing 100094, China;3. Graduate School, Chinese Academy of Sciences, Beijing 100049, China;4. Department of Geography and GeoInfomation Science, George Mason University, Fairfax, VA 22030, USA;1. State Key Laboratory of Structural Analysis for Industrial Equipment, Dalian University of Technology, 116024, China;2. Institute of Ocean Energy, Saga University, 840-8502, Japan;1. Pladema – CONICET, Universidad Nacional del Centro de la Provincia de Buenos Aires, Buenos Aires, Argentina;2. University Hospital of Tours, UMR Imagerie et Cerveau, Inserm U930, Université François-Rabelais, Tours, France |
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| Abstract: | The sound field in a circular pipe generated by a concentric jet flow entering the pipe is studied. In the first case the air flow enters the pipe through a convergent nozzle only. In the second case a short diffuser is attached to the nozzle. When the diffuser half angle is small enough to ensure attached flow conditions, the sound pressure level in the duct is reduced over the entire frequency range measured. When the diffuser angle is increased up to the point where flow separation occurs, an increase in the duct sound pressure level is observed. It is shown by means of cross-correlation measurements involving the unsteady wall pressures in the diffuser and the sound pressure in the duct that the increased sound levels are in fact caused by the flow separation in the diffuser. |
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