The geometrically complex mechanisms of energy transfer in the compound space of scales and positions of wall turbulent flows are investigated in a temporally evolving boundary layer. The phenomena consist of spatially ascending reverse and forward cascades from the small production scales of the buffer layer to the small dissipative scales distributed among the entire boundary layer height. The observed qualitative behaviour conforms with previous results in turbulent channel flow, thus suggesting that the observed phenomenology is a robust statistical feature of wall turbulence in general. An interesting feature is the behaviour of energy transfer at the turbulent/non-turbulent interface, where forward energy cascade is found to be almost absent. In particular, the turbulent core is found to sustain a variety of large-scale wall-parallel motions at the turbulent interface through weak but persistent reverse energy cascades. This behaviour conforms with previous results in free shear flows, thus suggesting that the observed phenomenology is a robust statistical feature of turbulent shear flows featuring turbulent/non-turbulent interfaces in general.

在随时间演化的边界层中研究了壁湍流尺度和位置复合空间中能量传递的几何复杂机制。该现象由空间上升的反向和前向级联组成，从缓冲层的小生产规模到分布在整个边界层高度的小耗散规模。观察到的定性行为与湍流通道流的先前结果一致，因此表明观察到的现象学通常是壁湍流的稳健统计特征。一个有趣的特征是湍流/非湍流界面处的能量传递行为，其中几乎不存在前向能量级联。特别是，湍流核心被发现通过微弱但持续的反向能量级联在湍流界面维持各种大规模的壁平行运动。这种行为与之前的自由剪切流结果一致，因此表明观察到的现象学是具有湍流/非湍流界面的湍流剪切流的稳健统计特征。