湍流边界层均匀动量区统计分形特性的PIV实验研究  

PIV EXPERIMENTAL STUDY ON STATISTICAL FRACTAL CHARACTERISTICS OF UNIFORM MOMENTUM ZONES IN TURBULENT BOUNDARY LAYER

作　　者：陈怡纯 田海平 马国祯 陈纪仲 Chen Yichun;Tian Haiping;Ma Guozhen;Chen Jizhong(Research and Innovation Center of Fluid Mechanics,Taiyuan University of Technology,Taiyuan 030024,China;National Demonstration Center for Experimental Mechanics Education,Taiyuan University of Technology,Taiyuan 030024,China)

机构地区：[1]太原理工大学流体力学科研创新中心,太原030024 [2]太原理工大学力学国家级实验教学示范中心,太原030024

出　　处：《力学学报》2024年第1期34-44,共11页Chinese Journal of Theoretical and Applied Mechanics

基　　金：国家自然科学基金(12172242,12332017,12302289);山西省基础研究计划(202203021222106)资助项目。

摘　　要：均匀动量区(UMZs)作为动量相近的局部区域成为新的湍流拟序结构成员,研究其统计特性与变化规律、分析其成因和研究其与其他湍流结构的内在关联,是深入认识壁湍流的重要途径.通过粒子图像测速系统(PIV)测量得到了具有高时空分辨率的湍流边界层流法向流场,对UMZs分区和界面位置等进行了统计,并基于瞬态流场分析了UMZs分界线与发卡涡(包)为主的湍流结构的位置关联,结果发现:UMZs流向速度概率密度函数(PDF)和界面厚度的统计分析呈现普适的分形特性,且不受湍流/非湍流界面(TNTI)和雷诺数的影响;瞬态流场UMZs数目在湍流间歇区较大,而湍流结构发展充分、层次丰富时的瞬态流场UMZs数目却较少;壁湍流涡包结构内多个发卡涡的空间分布规律决定了UMZs的统计分形特征;在近壁UMZs分界线向湍流结构存在区域集中靠拢,在外区UMZs分界线穿越展向涡核,正向涡旋导致UMZs分界线在法向上的聚集,反向涡旋引起UMZs分界线在流向上产生分离.Uniform momentum zones(UMZs),as local regions with similar momentum,become a new member of turbulent coherent structures.To study statistical characteristics,variation rules,its root causes and internal relationship with other turbulent structures about UMZs are an important way to understand wall turbulence.In this paper,the streamwise and wall-normal flow field of turbulent boundary with high spatio-temporal resolution was measured by time-resolved particle image velocimetry(TRPIV)system,statistical analysis was conducted on the partition and interface position of the UMZs.The position correlation between the UMZs boundary and the turbulent structure dominated by hairpin vortices(packets)was analyzed as well.The results revealed that the statistical analysis of streamwise velocity PDF and interface thickness of UMZs showed universal fractal characteristic,not affected by TNTI interfaces and Reynolds numbers.There are more UMZs number in the turbulent intermittent zone,and less UMZs number in instantaneous flow fields with well-developed turbulent structures with rich layers.The spatial distribution law of hairpin vortex packet determines the statistical fractal characteristics of the UMZs.The UMZs boundary near the wall converges towards the turbulent structure,while the UMZs boundary crosses the spanwise vortex core in the outer region.Forward spanwise vortex caused the aggregation of UMZs boundary in the wall-normal direction,while reverse spanwise vortex produced separation of UMZs boundary in the streamwise direction.

关 键 词：均匀动量区 分形特性 湍流结构 发卡涡包 

分 类 号：O357[理学—流体力学]