This paper presents a direct numerical simulation of turbulent flows over a bump in an open channel to examine the turbulence characteristics near divergent waves emanating from the bump and to investigate the interaction of the turbulences with the divergent waves. To verify the reliability of the simulations, the mean velocity profile and root-mean-square of velocity fluctuations are compared with previous data. The anisotropic invariant maps show that the ratio of the streamwise to spanwise velocity fluctuations plays an important role in characterizing the anisotropic nature of the separated shear layer behind the bump in the vicinity of the free surface. The vortex identification discloses a large-scale streamwise vortical structure from the mean velocity field and a cluster of small coherent structures from the instantaneous velocity field, which are responsible for the anisotropic characteristics of the turbulence beneath the free surface.

本文提出了在明渠中颠簸上方湍流的直接数值模拟，以检查颠簸产生的发散波附近的湍流特性，并研究湍流与发散波的相互作用。为了验证模拟的可靠性，将平均速度曲线和速度波动的均方根与以前的数据进行了比较。各向异性不变图显示，在表征自由表面附近凸块后面的分离剪切层的各向异性特性中，沿流速度与沿跨度速度波动的比率起着重要作用。涡流识别从平均速度场公开了大规模的流向涡流结构，并从瞬时速度场公开了一组小的相干结构，