A Parametric Study of the Link between Energy Dissipation and Bubble Creation in Laboratory Breaking Waves

实验室碎波中能量耗散与气泡产生之间联系的参数化研究

• 批准号: 0450974
• 负责人: Grant Deane
• 金额: $ 52.8万
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-04-01 至 2008-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0450974&HistoricalAwards=false
• 关键词: Parametric; Study; Link; between; Energy

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.

Abstractoce-0450974这项研究的目的是研究实验室断裂波中的能量耗散与泡泡创造之间的联系。通过破坏波的能量耗散是许多重要的上海洋过程的关键，包括动量转移和气泡介导的空气海气传输。这项研究以早期的NSF赠款的结果为基础，以识别波峰中断的泡沫创造机制。较早的研究确定了暴跌破裂器中气泡创造过程的尺度依赖性：大于长度尺度的气泡由湍流压力波动的碎裂力和表面张力的稳定力（Hinze尺度）确定的比例大于碎裂事件。小于Hinze量表的气泡因湍流碎片化而稳定。在本研究中要解决的两个主要问题是：1）破裂波峰中消散的湍流能量如何随波能和波斜率的变化而变化，而2）Hinze量表会按预期的固有波能量耗散而变化？ 该研究计划包括测量各种波能量和斜率的断裂波峰中的能量耗散，以及估算湍流气泡碎片的hinze量表，作为能量耗散的函数。能量耗散的估计值将通过研究玻璃墙水槽中的断裂波数据包来获得一系列波能和斜率，这会因改变数据包的频谱组成而变化。破裂波峰区域内的能量耗散率将通过两种方法独立估计：对生物发光鞭毛藻的光发射和能量保存的定量分析。使用生物发光来量化湍流是一种最近的技术，但事实证明对暂时性，两个相流有效。破裂过程中的气泡尺寸分布和空气的空隙分数将使用光学技术和电导率电池获得。气泡HINZE量表对应于气泡尺寸分布的斜率的明显变化，可以从光学测量中估算出来。断裂过程中损失的总能量将根据在破裂的上游和下游测量的波数据包形状的变化来估计，并且在破裂结束时相干和湍流的流体运动中的残留能量将通过声学多普勒速度仪和集合平均多个事件来测量。 更广泛的影响。 该项目将增强对大气动量向海洋的理解，控制气体传输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。所有这些过程都对大气 - 海洋耦合动态，全球气候建模和沿海海洋学产生了广泛的影响。实验和数据分析将包括UCSD和SIO Summer Research奖学金计划的研究生和本科实习生的参与。这些计划赞助来自全国各地的学生，以获得海洋学的动手经验。研究小组与加利福尼亚海洋科学教育中心合作，还与海洋研究所（Sea Bubbles！）制定了一项外展计划，以增加公众对海洋 - 大气相互作用的了解。