摘要
波包被认为是喷流中一种重要的声辐射源,运动学分析旨在建立波包运动与声辐射的关联模型,但是该模型对于非等温喷流还存在表征波包尺度变化的问题。本文通过对速度、密度与压强场的模态分析来筛选适合于表征非等温喷流中波包的物理量,进一步引入了一种表征波包尺度变化的连续函数,在此基础上讨论波包尺度对声辐射的影响。结果表明喷流温度使得压强模态与密度模态的同步特征消失,且改变了压强模态与速度模态之间的耦合关系。压强模态的辐射特征显著,因此运动学分析可以针对压强场来开展。波包包络尺度L和相干衰减尺度Lc使得波包的能量分布呈椭圆形分散到辐射区,从而提高了波包的辐射强度。L仅使得椭圆端部畸变,它对辐射强度的影响比Lc弱。
Wave-packets have been considered as important sound sources of jet noise,ever since they were observed in experiments.Kinematic analyses aim to model the sound radiation based on motions of the wave-packets.However,for non-isothermal jets,the variation of length scales in wave-packets are not included by the original model.In this paper,modal analyses are carried out for the fields of velocity,density and pressure,in order to find a suitable variable to represent the wave-packets in non-isothermal jets.A continuous function is introduced,to represent the variable length scales of wave-packets,and the effects of length scales to the sound radiation are discussed.Results show that the temperature of jet flow desynchronizes the modes of density and pressure,and it also changes the coupling between modes of velocity and pressure.The pressure mode presents salient radiation feature,so the pressure field is meaningful for the kinematic analyses.The length scale of amplitude envelope,L,together with the length scale of coherence decay,Lc,cause the energy distribution of the wave-packet as an ellipse whose end scatters into a radiation region.Thus,the radiation intensity of the wave-packet is enhanced.The L only distorts the end of the ellipse slightly,showing a weaker effect on the radiation intensity than that of the Lc.
作者
刘琪麟
赖焕新
LIU Qilin;LAI Huanxin(School of Mechanical and Power Engineering,East China University of Science and Technology,Shanghai 200237,China)
出处
《工程热物理学报》
EI
CSCD
北大核心
2023年第12期3272-3282,共11页
Journal of Engineering Thermophysics
基金
国家自然科学基金资助项目(No.51976061)。
关键词
非等温喷流
波包
相干结构
尺度
non-isothermal jet
wave-packet
coherent structure
length scale
