Periodic motion embedded in plane Couette turbulence: regeneration cycle and burst
Periodic motion embedded in plane Couette turbulence: regeneration cycle and burst
复制标题
DOI：
10.1017/s0022112001006243
复制
发表时间：
2001-12-25
影响因子：
3.7
通讯作者：
Kida, S
中科院分区：
文献类型：
--
作者：
Kawahara, G;Kida, S
数值求解了受约束平面Couette流的不可压Navier-Stokes方程的两个具有三维结构的时间周期解。一个解决方案具有强烈的变化，在空间和时间结构表现出完整的再生周期，其中包括形成和崩溃的流向涡和低速条纹;另一个，温和的变化，代表展向驻波运动的低速条纹。这两个解是不稳定的，并且相空间中相应的周期轨道是相互连接的。湍流状态在大部分时间内都在强湍流状态附近徘徊，偶尔也会从强湍流状态中逃逸出来，因此，平面Couette湍流的平均速度分布和速度脉动的均方根值与这种周期运动的时间平均值吻合得很好。在偶尔逃离强解之后，湍流状态到达温和的周期解并返回。在返回的途中，它经历了一次过冲，伴随着强烈的湍流活动，就像间歇性的爆发现象。
Two time-periodic solutions with genuine three-dimensional structure are numerically discovered for the incompressible Navier-Stokes equation of a constrained plane Couette flow. One solution with strong variation in spatial and temporal structure exhibits a full regeneration cycle, which consists of the formation and breakdown of streamwise vortices and low-velocity streaks; the other one, of gentle variation, represents a spanwise standing-wave motion of low-velocity streaks. These two solutions are unstable and the corresponding periodic orbits in the phase space are connected with each other. A turbulent state wanders around the strong one for most of the time except for occasional escapes from it. As a result, the mean velocity profile and the root-mean-squares of velocity fluctuations of the plane Couette turbulence agree very well with the temporal averages of those of this periodic motion. After an occasional escape from the strong solution, the turbulent state reaches the gentle periodic solution and returns. On the way back, it experiences an overshoot accompanied by strong turbulence activity like an intermittent bursting phenomenon.