An experimental investigation of the effects of wind and wave on the impact of raindrops on water surface

海洋上空降水产生的海-气边界层在水-气界面的质量、热量、能量和动量的传输中起着重要的作用。雨场中的这种海-气边界层包括雨滴撞击产生的次生水滴、茎、冠和表面波。在实验室的两个不同的设备(雨塔和风浪水箱)中，在不同的风浪条件下，进行了不同雨量、雨滴直径和降雨在水面上的空间分布的实验。由于海洋上的降雨对影响天气和气候的海气转移过程做出了重要贡献，这项研究将产生广泛的影响。该项目将通过支持一名研究生和两名本科生，为理科学生的教育做出贡献。PIS还将向本科生班级介绍这项研究，并在每学期为当地高中生举办一次约一次讲座或一次实地访问，以向他们介绍这项研究的主题领域。希望这能培养他们在大学学习中学习海洋学的兴趣。此外，这项研究的结果将被发布在网络、照片和视频上，并将提交给美国物理学会流体运动画廊(APS)。本画廊的获奖者将发表在APS流体动力学分部的网站上。测量将包括使用电影激光诱导荧光技术测量雨场中心平面上的茎、冠和表面波的轮廓历史，使用全息技术测量雨滴和二次液滴的大小和轨迹，以及使用脉冲超宽带雷达系统测量雨区水面的雷达后向散射。实验室实验的目的是研究风浪对雨场中海-气边界层流动特性和混合特性的影响。研究了海气边界层在雨场中的变化对雷达后向散射特征的影响。模拟海-气输送过程的努力主要取决于湿度和蒸发量，而湿度和蒸发量又因降雨而大大增强。通过利用从拟议的实验中学到的物理知识，这项研究的目的是在风和海浪如何影响雨场中的海-气边界层的认识和理解方面取得重要进展，并做出重要贡献，数值模拟人员将发现这一点是有用的。最后，测量降雨对水面影响的技术进步将产生于拟议的工作，并将适用于与流体力学相关的其他领域的类似测量。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The air-sea boundary layer generated by rainfall over the ocean plays an important rolein the transfer of mass, heat, energy and momentum across the air-water interface. This air-sea boundary layer in the rain field includes secondary droplets, stalks, crowns and surface waves that are generated by the impacts of rain drops. Experiments with various rain rates, rain drop diameters and spatial distributions of rain on the water surface will be carried out in two different facilities (rain tower and wind-wave tank) in a laboratory under various conditions of wind and waves. Since rainfall over the ocean makes an important contribution to air-sea transfer processes that affect weather and climate, the research will have a broad impact. The project will contribute to the education of students in the sciences by supporting one graduate student and two undergraduate students. The PIs will also introduce the research to undergraduate classes and give approximately one talk or host one field visit to their research laboratory for local area high school students each semester in order to introduce them to the subject area of this research. It is hoped that this may foster interest in pursuing oceanography in their university studies. Also, results from this research will be posted on the web and photographs and videos and will be submitted to the Gallery of Fluid Motion of the American Physical Society (APS). Winners of this Gallery are published and posted on the web of the APS Division of Fluid Dynamics.Measurements will include the profile histories of stalks, crowns and surface waves at the center plane of the rain field using a cinematic laser induced fluorescence technique, the sizes and trajectories of both rain drops and secondary droplets using a holographic technique, and radar backscattering from the water surface in the rain zones using a pulsed ultra-wide band radar system. The goal of the laboratory experiments is to investigate the effects of wind and waves on the flow properties and mixing characteristics of the air- sea boundary layer in a rain field. The radar backscattering signatures in response to the changes of the air-sea boundary layer in the rain field will be investigated as well. Efforts to model air-sea transfer process are critically dependent on humidity and evaporation which are in turn greatly enhanced by rainfall. By using the physics learned from the proposed experiments, this study aims to produce important advancement in knowledge and understanding of how wind and waves affect the marine-atmospheric boundary layer in a rain field and make an important contribution that numerical modelers will find useful. Finally, advances in techniques for the measurement of rain impact on the water surface will result from the proposed work and will be applicable to similar measurements in other fields related to fluid mechanics.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.