论文标题
风流水流中表面条纹的产生和分解
Generation and Breakdown of Surface Streaks in Wind-Driven Aqueous Flow
论文作者
论文摘要
使用具有加速表面漂移速度的时间增长的边界层模型分析了风压力驱动的水流中的旁路过渡方案。选择模型的参数以模拟波坦克实验，参考风速为5 m/s。为了分别研究边界层过程，对平坦的自由表面进行了调整，从而抑制了波的启动。首先，使用线性非正常生长理论确定边界层最敏感的优选初始扰动。这些扰动被排列为位于自由表面附近的流轴结构涡流对。随后，使用这些最佳扰动初始化了直接的数值模拟，并生成流式条纹。高速条纹渗透到更深的水层中，并让人弯曲的不稳定性让人联想到壁挂式流中低速条纹上发展的不稳定性。条纹不稳定性在自由表面诱导横向起伏，在风波坦克实验中波发作之前，它与染料模式非常相似。目前的分析为这些实验观察提供了理论背景。
A bypass transition scenario in a wind-stress driven aqueous flow is analysed using a temporally developing boundary layer model with accelerating surface drift velocity. The parameters of the model are selected to mimic a wave-tank experiment with a reference wind speed of 5 m/s. To study the boundary layer processes in isolation, a flat free surface is adapted, which inhibits the initiation of waves. First, preferred initial perturbations to which the boundary layer is the most sensitive are identified using linear non-normal growth theory. These perturbations are arranged as streamwise-constant vortex pairs located adjacent to the free surface. Subsequently, direct numerical simulations are initialized with these optimal perturbations and streamwise streaks are generated. High-speed streaks penetrate into deeper water layers and undergo sinuous instabilities reminiscent of the instabilities developing on low-speed streaks in wall-bounded flows. Streak instabilities induce lateral undulations at the free surface, which closely resemble the dye patterns before the onset of waves in wind-wave-tank experiments. The present analysis provides a theoretical background for these experimental observations.
