Direct numerical simulations of a turbulent Couette-Poiseuille flow with zero-mean-shear at the moving wall (SL-flow) is performed to examine flow features compared to those for a turbulent pure Poiseuille flow (P-flow). Profiles of the streamwise mean velocity, indicator function and ratio of production to dissipation show that the logarithmic region is significantly elongated for the SL-flow compared to that for the P-flow at a similar Reynolds number. In addition, the magnitudes of the Reynolds stresses are found to be larger in both inner and outer layers for the SL-flow than those for the P-flow. The spanwise spectra of the production term in the turbulent kinetic energy equation are examined to provide a structural basis for explaining the statistical behaviors. In addition, because the growth of the energy-containing motions extends to the outer layer further for the SL-flow due to the presence of a positive mean shear throughout the entire wall layer, the self-similar behavior of the energy balance between the production and transport terms with respect to the self-similar wavenumber is found far from the wall. We also find the increase in the number of uniform momentum zones in the SL-flow, revealing the hierarchical distribution of the energy-containing eddies which are composed of multiple uniform momentum zones. These coherent motions lead to the elongation of the logarithmic region for the SL-flow. Finally, investigation of the turbulent energy transfer process in a spectral domain for the SL-flow demonstrates importance of outer layer very-long structures, and these structures attribute to the energy transport process in an entire flow field.

对在移动壁上具有零平均剪切的湍流 Couette-Poiseuille 流 (SL 流) 进行直接数值模拟，以检查与湍流纯 Poiseuille 流 (P 流) 相比的流动特征。流向平均速度、指示函数和生产与耗散比的剖面图表明，在相似雷诺数下，SL 流的对数区域比 P 流的对数区域显着延长。此外，发现 SL 流的内层和外层雷诺应力的大小都比 P 流的大。检查了湍流动能方程中产生项的展向谱，以提供解释统计行为的结构基础。此外，由于在整个壁层中存在正平均剪切，因此对于 SL 流，含能运动的增长进一步扩展到外层，因此产生和传输项之间的能量平衡的自相似行为关于自相似波数被发现远离壁面。我们还发现 SL 流中均匀动量区的数量增加，揭示了由多个均匀动量区组成的含能涡流的分层分布。这些相干运动导致 SL 流的对数区域的伸长。最后，对 SL 流谱域中的湍流能量传递过程的研究证明了外层超长结构的重要性，