Research in Linear and Nonlinear Baroclinic Waves and Ocean Circulation Theory

本研究的目的是研究实验室破碎波中能量耗散和气泡产生之间的联系。破碎波的能量耗散是一些重要的海洋上层过程的关键，包括动量转移和气泡介导的海气输送。这项研究建立在早期NSF资助的结果基础上，以确定破碎波峰内的气泡产生机制。早期的研究确定了尺度依赖性的气泡产生过程中暴跌断路器：气泡大于长度尺度的湍流压力波动的破碎力和表面张力的稳定力（Hinze规模）的比例确定的受到一系列的破碎事件。小于Hinze尺度的气泡是稳定的，对湍流破碎。在这项研究中要解决的两个主要问题是：1）如何在破碎波峰耗散的湍流能量随波能和波斜率的变化而变化？2）欣泽尺度是否随预测的内禀波能耗散而变化？ 研究计划包括测量各种波能和坡度的破碎波峰内的能量耗散，并估计作为能量耗散函数的湍流气泡破碎的Hinze尺度。能量耗散的估计将通过研究破碎波包在玻璃壁水槽的波能和斜率的范围内，通过改变包的光谱组成而变化。破碎波峰区域内的能量耗散率将独立估计两种方法：定量分析发光甲藻的光发射，和能量守恒。使用生物发光来量化湍流是一种最近的技术，但已被证明对瞬态两相流是有效的。将使用光学技术和电导池获得破碎过程中的气泡尺寸分布和空气的空隙率。气泡Hinze尺度对应于气泡尺寸分布的斜率的显著变化，其可以从光学测量估计。破碎过程中损失的总能量将从破碎上游和下游测得的波包形状的变化来估计，破碎结束时相干和湍流流体运动中的剩余能量将用声学多普勒速度计和多个事件的整体平均来测量。 更广泛的影响。 该项目将增进对大气动量向海洋的输送、控制气体输送的小规模物理过程以及海洋边界层和沿海地区的湍流和气泡产生的了解。所有这些过程都对大气-海洋耦合动力学、全球气候模拟和沿海海洋学产生了广泛的影响。实验和数据分析将包括来自UCSD和SIO夏季研究奖学金计划的研究生和本科实习生的参与。这些项目赞助来自全国各地的学生获得海洋学方面的实践经验。该研究小组与加州海洋科学教育卓越中心合作，还与海洋研究所（海洋泡沫！）以增加公众对海洋-大气相互作用的了解。

ABSTRACTOCE-0450974The objective of this research is to study the link between energy dissipation and bubble creation in laboratory breaking waves. Energy dissipation by breaking waves is key to a number of important upper-ocean processes, including momentum transfer and bubble-mediated air-sea gas transport. This study builds on the results of an earlier NSF grant to identify bubble creation mechanisms within breaking wave crests. The earlier study identified the scale dependence of bubble creation processes within plunging breakers: bubbles larger than a length scale determined by the ratio of the fragmenting forces of turbulent pressure fluctuations and the stabilizing force of surface tension (the Hinze scale) are subject to a cascade of fragmentation events. Bubbles smaller than the Hinze scale are stabilized against turbulent fragmentation. The two main questions to be addressed in this study are: 1) how does the turbulent energy dissipated in the breaking wave crest vary with variations in wave energy and wave slope and 2) does the Hinze scale vary with intrinsic wave energy dissipation as predicted? The research plan consists of measuring of energy dissipation within breaking wave crests for various wave energies and slopes, and estimating the Hinze scale for turbulent bubble fragmentation as a function of energy dissipation. Estimates of energy dissipation will be obtained by studying breaking wave packets in a glass-walled flume for a range of wave energies and slopes, varied by changing the spectral composition of the packets. The energy dissipation rate within the breaking crest region will be independently estimated with two methods: quantitative analysis of the light emission from bioluminescent dinoflagellates, and conservation of energy. Using bioluminescence to quantify turbulence is a recent technique, but has proven effective for transitory, two phase flows. The bubble size distribution and void fraction of air during breaking will be obtained using optical techniques and a conductivity cell. The bubble Hinze scale corresponds to a distinctive change in slope of the bubble size distribution, which can be estimated from the optical measurements. The total energy lost during breaking will be estimated from changes in wave packet shape measured upstream and downstream of breaking, and the residual energy in coherent and turbulent fluid motions at the end of breaking will be measured with acoustic Doppler velocimeters and ensemble averaging of multiple events. Broader Impact. The project will enhance the understanding of atmospheric momentum transport to the ocean, the small-scale physical processes controlling gas transport, and turbulence and bubble production in the marine boundary layer and coastal regions. All of these processes have a broad impact on atmosphere-ocean coupling dynamics, global climate modeling and coastal oceanography. The experiment and data analysis will include the participation of a graduate student and undergraduate interns from UCSD and the SIO summer research fellowship program. These programs sponsor students from around the country to gain hands-on experience in oceanography. Working with the California Center for Ocean Science Education Excellence, the research team is also developing an outreach plan with the Ocean Institute (Sea Bubbles!) so as to increase public understanding of ocean-atmospheric interactions.