Coherent vortices in the aqueous surface layer beneath wind waves manifest themselves by inducing elongated high-speed streaks on the interface. Analyses of thermal images taken in the wind-wave flume reveal that the mean streak spacing scaled by the viscous length, , depends strongly on the wind-wave condition. This contradicts the wall-bounded turbulent flow in which the scaled mean streak spacing approaches a canonical value, . Comparative numerical simulations of shear flow bounded by flat and wavy surfaces are conducted to explain the variation. In the low-wind range with insignificant surface waves, ; the reduction of is attributed to the insufficient shear rate to form the elongated streaks. For the moderate-wind range in which surface waves become pronounced but remain to be unbroken, is still less than 100. Analysis of the vorticity transport in the simulated wavy flows reveals that the presence of non-breaking waves enhances the formation of quasi-streamwise vortices and the surface streaks. For the high-wind range, surface waves break and the breakers wipe out the streaks. The streaks quickly reestablish in the wake of the breaker with mean spacing but are destructed again by the following breaker.

中文翻译：

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风波上条纹状热足迹的特征

风波下方的水表面层中的相干涡流通过在界面上引起细长的高速条纹而表现出来。对风浪水槽中拍摄的热图像的分析表明，由粘性长度 缩放的平均条纹间距在很大程度上取决于风浪条件。这与壁限湍流相矛盾，其中缩放的平均条纹间距接近规范值。进行了以平坦和波浪形表面为界的剪切流的比较数值模拟来解释这种变化。在低风区，面波微不足道，；减少归因于剪切速率不足以形成拉长的条纹。对于表面波显着但仍未中断的中风范围，仍小于 100。 对模拟波浪流中涡度输运的分析表明，非中断波的存在增强了准流向的形成涡流和表面条纹。对于强风范围，表面波会破裂，而破碎带会消除条纹。条纹在具有平均间距的破碎机之后迅速重新建立，但被下一个破碎机再次破坏。