SGER: Documenting the Transient Nature of Natural Free Convection in Groundwater

SGER：记录地下水中自然自由对流的瞬态性质

• 批准号: 0903508
• 负责人: David Hyndman
• 金额: $ 4.91万
• 依托单位: Michigan State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-06-01 至 2011-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0903508&HistoricalAwards=false
• 关键词: SGER; Documenting; Transient; Nature; Natural

Geophysical imaging of a sabkha in the United Arab Emirates (UAE) following an extreme precipitation event in 2008 shows the first compelling evidence of free convection flow processes in a natural groundwater setting. The imaged pattern is consistent with fingering caused by precipitation-induced redissolution of a halite crust and a pre-existing convection pattern; the distribution of these fingers is similar to those observed in lab experiments and numerical simulations. Natural free convection, which is important for heat and solute transport across a range of hydrogeologic settings, has been studied for over a century but almost entirely in theory, numerical models, and laboratory experiments. Currently, very little is known about the growth and decay of convective instabilities because most research assumes steady state conditions. In order to resolve key questions about origins and persistence of convection, as well as their associated spatial and temporal scales, it is vital to resolve the transient nature of different interacting regimes.Our UAE field site is an ideal location to address some of these knowledge gaps. Precipitation records suggest that fingering at this site may only be initiated once every decade with a halite crust building up during dryer years. Our pilot data demonstrate the unique opportunity to monitor the dynamic nature of density fingering. We propose to integrate time-lapse geophysical, hydrological, and geochemical measurements with preliminary hydrological modeling. The exploratory research will provide a transformative advance for this important field. The results will be disseminated through research papers and conference presentations and will form the foundation for a continued research program including a full-scale modeling effort.

在2008年极端降水事件之后，阿拉伯联合酋长国（UAE）sabkha的地球物理成像显示了天然地下水环境中自由对流过程的第一个令人信服的证据。成像模式是一致的指状所造成的沉淀引起的再溶解的岩盐地壳和预先存在的对流模式，这些手指的分布是类似于在实验室实验和数值模拟中观察到的。自然自然对流是水文地质条件下热量和溶质运移的重要因素，人们对自然对流的研究已经有世纪之久，但几乎完全是在理论、数值模型和实验室实验中进行的。目前，对对流不稳定性的增长和衰减知之甚少，因为大多数研究假设了稳态条件。为了解决对流的起源和持续性以及相关的空间和时间尺度的关键问题，解决不同相互作用机制的瞬态性质至关重要。我们的阿联酋现场是解决这些知识差距的理想场所。降水记录表明，在这个网站的指入可能只会开始每十年一次，在干燥的几年与岩盐地壳建设。我们的试验数据证明了监测密度指进动态性质的独特机会。我们建议将延时地球物理，水文和地球化学测量与初步水文建模相结合。探索性研究将为这一重要领域提供变革性的进展。研究结果将通过研究论文和会议演示进行传播，并将为包括全面建模工作在内的持续研究计划奠定基础。