On hairpin vortex generation from near-wall streamwise vortices
The generation of a hairpin vortex from near-wall streamwise vortices is studied via the direct numerical simulation(DNS)of the streak transient growth in the minimal channel flow at Reτ = 400.The streak profile is obtained by conditionally averaging the DNS data of the fully developed turbulent channel flow at the same Reynolds number.The near-wall streamwise vortices are produced by the transient growth of the streak which is initially subjected to the sinuous perturbation of the spanwise velocity.It is shown that the arch head of the hairpin vortex first grows from the downstream end of the stronger streamwise vortex and then connectswith theweaker,opposite-signed streamwise vortex in their overlap region,forming a complete individual hairpin structure.The vorticity transport along the vortex lines indicates that the strength increase and the spatial expansion of the arch head are due to the stretching and the turning of the vorticity vector,respectively.The hairpin packets could be further produced from the generated individual hairpin vortex following the parent-offspring process.
Hairpin vortex Streamwise vortex Streak transient growth
Yinshan Wang Weixi Huang Chunxiao Xu
AML,Department of Engineering Mechanics,Tsinghua University,Beijing 100084,China
国内会议
上海
英文
139-152
2017-12-16（万方平台首次上网日期，不代表论文的发表时间）