Scientific Research and Essays

  • Abbreviation: Sci. Res. Essays
  • Language: English
  • ISSN: 1992-2248
  • DOI: 10.5897/SRE
  • Start Year: 2006
  • Published Articles: 2748

Full Length Research Paper

Flow-induced Noise Prediction for 90ËšBend Pipeby LES and FW-H Hybrid Method

Zhang Chunjian
  • Zhang Chunjian
  • School of Engineering, Sun Yat-sen University, Guangzhou 510006, China.
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Luo Yuxi
  • Luo Yuxi
  • School of Engineering, Sun Yat-sen University, Guangzhou 510006, China.
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Liang Jiuxing
  • Liang Jiuxing
  • School of Engineering, Sun Yat-sen University, Guangzhou 510006, China.
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Li Lala
  • Li Lala
  • School of Engineering, Sun Yat-sen University, Guangzhou 510006, China.
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Li Jiang
  • Li Jiang
  • Department of Mathematics, University of Connecticut, Storrs 06269, USA.
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  •  Received: 10 March 2014
  •  Accepted: 29 April 2014
  •  Published: 15 June 2014

Abstract

This paper focuses on an aerodynamic noise study of outlet elbow of Continuous Positive Airway Pressure (CPAP) machine by analyzing the wall pressure fluctuations and predicting the far filed sound generated by turbulent flow. A hybrid approach combing the Larger-Eddy Simulation (LES) and Ffcowcs Williams-Hawkings (FW-H) acoustic analogy was used to simulate the flow distribution as well as calculate the flow-induced noise for a three-dimensional elbow pipe. Then, a different elbow structure was designed to form the appropriate structure for the air outlet via considering the sound pressure level of each model. As a result, elbow with guiding plate was demonstrated to be an effective method to reduce the aerodynamic noise strength since this design could weaken the wall pressure fluctuation and vortex magnitude. Furthermore, the decreased magnitude could reach more than 1dB when velocity increased from 5m/s to 9m/s. The results of simulation were a little higher than experimental results since the background noise, elbow vibration and the defect of FW-H equation which couldn’t be eliminated thoroughly.
 
Key words: Exhaust elbow, aerodynamic noise, Large-Eddy simulation, guiding plate, FW-H Acoustic Analogy