Momentum flux measurements in the airflow over wind-generated surface waves
Momentum flux measurements in the airflow over wind-generated surface waves
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DOI：
10.1017/jfm.2020.276
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发表时间：
2020-05
影响因子：
3.7
通讯作者：
K. Yousefi;F. Veron;M. Buckley
中科院分区：
文献类型：
--
作者：
K. Yousefi;F. Veron;M. Buckley
表面波存在时的海气动量交换在大气和海洋的耦合中发挥着不可或缺的作用。在当前的研究中，我们对风生波的动量通量进行了详细的实验室研究。实验是在特拉华大学海气相互作用实验室的大型风浪设施中进行的。使用粒子图像测速和激光诱导荧光技术相结合，在风波上方获得气流速度测量结果。使用波跟随正交曲线坐标系检查动量预算。在波边界层，波峰的相平均湍流应力强（弱），顺风（逆风）为正。波峰的迎风面和背风面的波浪诱发应力也为正值，但强度不对称。这些正波应力区域与波峰上方和波谷顺风处的负波应力区域交织在一起。同样，在界面处，粘性应力表现出沿波锁相变化，且波峰逆风向最大。作为一般趋势，波致应力的平均分布从远离表面的接近零值减小到负最小值，然后在湍流应力减小的界面附近快速增加到正值。然而，远离表面时，湍流应力几乎等于总应力。在非常接近表面的粘性子层中，波应力和湍流应力消失，因此应力由粘性支撑。
The air–sea momentum exchanges in the presence of surface waves play an integral role in coupling the atmosphere and the ocean. In the current study, we present a detailed laboratory investigation of the momentum fluxes over wind-generated waves. Experiments were performed in the large wind-wave facility at the Air–Sea Interaction Laboratory of the University of Delaware. Airflow velocity measurements were acquired above wind waves using a combination of particle image velocimetry and laser-induced fluorescence techniques. The momentum budget is examined using a wave-following orthogonal curvilinear coordinate system. In the wave boundary layer, the phase-averaged turbulent stress is intense (weak) and positive downwind (upwind) of the crests. The wave-induced stress is also positive on the windward and leeward sides of wave crests but with asymmetric intensities. These regions of positive wave stress are intertwined with regions of negative wave stress just above wave crests and downwind of wave troughs. Likewise, at the interface, the viscous stress exhibits along-wave phase-locked variations with maxima upwind of the wave crests. As a general trend, the mean profiles of the wave-induced stress decrease to a negative minimum from a near-zero value far from the surface and then increase rapidly to a positive value near the interface where the turbulent stress is reduced. Far away from the surface, however, the turbulent stress is nearly equal to the total stress. Very close to the surface, in the viscous sublayer, the wave and turbulent stresses vanish, and therefore the stress is supported by the viscosity.