摘要
本文采用热线风速仪测量了出口雷诺数为Re(≡Ujd/ν)=20100的圆形射流的中心线轴向速度,其中Uj为动量平均出口速度,d为喷嘴出口直径,ν为运动黏性系数.在有效去除热线测量数据中的高频噪声后,作者对射流中心线上小尺度湍流统计量的变化规律进行了系统的分析.研究发现,射流在经过一定距离的发展后,其小尺度统计量逐渐进入自相似状态,湍动能平均耗散率ε随下游距离的增加以指数形式衰减,Kolmogorov尺度η,Taylor尺度λ与下游距离的变化呈线性关系,湍流雷诺数Reλ以及速度一阶导数的偏斜因子S与平坦因子K均趋于常数.与前人结果相比,本文所获得的湍流自相似关系式中的比例系数更为严谨、合理,同时作者还发现,相比于湍流的大尺度运动,湍流的小尺度运动能更早地发展到自相似状态,并且湍流最小尺度统计量的变化规律更具有普遍性.此外,本文还分析了噪声对这些小尺度湍流统计量的影响,对今后湍流小尺度研究的实验测量具有指导意义.
This study systematically investigates the statistics of the centreline small-scale turbulence of a circular jet issuing from a smooth contraction nozzle. Detailed velocity measurements were performed for the exit Reynolds number of Re = 20100,where Re≡Ujd /ν with Uj being the exit mean velocity,d the nozzle diameter and ν the kinematic viscosity. After effectively filtering out high frequency noises, statistical properties of the small-scale turbulence were obtained appropriately; those properties include turbulence energy dissipation rate, Kolmogorov length scale, Taylor scale, turbulence Reynolds number,skewness and flatness of the velocity derivative. It is observed that these properties satisfy their self-preserving relations in the far field. It is also revealed that the small-scale turbulence reaches the self-preserving state earlier than does the large-scale motion. Besides,the smallest-scale turbulence depends least on the initial and boundary conditions and therefore behaves most universally across different flows.
出处
《物理学报》
SCIE
EI
CAS
CSCD
北大核心
2011年第3期376-384,共9页
Acta Physica Sinica
基金
国家高技术研究发展计划(批准号:2007AA05Z300)资助的课题~~
关键词
恒温热线
圆形湍射流
耗散率
小尺度
hot-wire anemometer
circular jet
dissipation rate
small-scale turbulence
