基于大涡模拟和Lighthill声类比的孔腔流动发声特性研究

孔腔流动发声是气动声学研究领域重要的课题,基于大涡模拟和Lighthill声类比方法,探讨了气体在孔腔流动的流激噪声的发声特性。模拟结果表明,孔腔边界层出口剪切涡、边棱处涡街和腔体内反馈涡的运动诱导了孔腔发声,具有明显的偶极子特性,在高频段腔体内激发了声学驻波模态。通过模拟与实验对比分析了不同流量下噪声量级以及频谱分布规律,研究结果表明:24 kHz以下的声频谱会表现出波峰小范围迁移;24 kHz以上频率对应的声压级随流量增大而增大;腔体长度和特征频率近似满足Strouher公式,即声频特征频率随腔体长度的增大而减小。上述研究结果为下一步设计在线监测安全阀泄漏的报警超声波发声器提供了理论依据。

Research on the characteristics of sound generated by flow inside cavity based on LES and Lighthill acoustic analogy method

Cavity flow is an important issue in the field of aeroacoustics. By using LES (large eddy simulation) and Lighthill acoustic analogy method, the characteristics of sound generated by flow inside cavity have been discussed. Simulation results show that the sound generated by shear vortex, edge vortex and feedback vortex has obvious dipole characteristics. Acoustic standing wave is excited at high frequency. By simulation and experiment, the magnitude of noise and the distribution of spectrum under different flow rates are analyzed. The results show that the acoustic frequency locking characteristic could happen under different paraments of cavity length, diameter and baffle length, and that the frequency spectrum has a small range migration of the peak below 24 kHz and the sound pressure level increases with the flow rate above 24 kHz. The relation between cavity length and characteristic frequency is approximately satisfied with Strouher''s formula, and the characteristic frequency decreases with increasing the length of cavity. The research provides a theoretical basis for the design of the ultrasonic safety valve leakage alarm system for on-line monitoring.