轴对称钝体前缘分离剪切层的非线性行为

实验研究了锐前缘轴对称钝体前缘分离剪切层发展演化的动力学过程,以及分离剪切层与外加声激励之间的非线性作用.研究结果表明,自然状态下,存在着亚谐频现象,分离剪切层的演化发展是通过涡合并方式实现的.从分离到再附,层流分离剪切层一般经过2次涡合并过程,湍流分离剪切层一般经过5次涡合并过程.混沌动力学分析表明,层流分离剪切层是经过Hopf分岔和周期倍分岔途径进入混沌状态的.此外,讨论了分离剪切层对外加声激励的响应.

Nonlinear Behavior of Separated Shear Layer of a Blunt Circular Cylinder

Dynamical evolution process of separated shear layer of a blunt circular cylinder,and nonlinear interaction between separated shear layer and acoustic forcing have been experimentally investigated. The researches demonstrate, in unexcited state, there exists the subharmonic phenomenon, which implies the evolution of separated shear layer is mainly through vortices merging process. From separation to reattachment, laminar separated shear layer will take 2 times vortices merging processes, and turbulence separated shear layer will experience 5 times vortices merging. From the point of view of nonlinear dynamical system, transition of separated shear layer from order to chaos is through Hopf bifurcation and periodical bifurcation. In addition, response of separated shear layer to acoustic forcing was discussed.