Coupled Heat and Water Transfer in Soil

土壤中的热水耦合传递

• 批准号: 0337553
• 负责人: Robert Horton
• 金额: $ 35.02万
• 依托单位: Iowa State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-02-15 至 2008-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0337553&HistoricalAwards=false
• 关键词: Coupled; Heat; Water; Transfer; Soil

0337553HortonMovement of heat and water across the soil surface largely drives both the atmosphere and the terrestrial hydrosphere. In near-surface soil, coupled transfer of heat and water is the rule rather than the exception, yet the coupling process is poorly understood. In fact, predictions made using the de facto standard Philip and de Vries type coupled transfer model can be substantially off. Current models, based as they are on data sets covering only a narrow range of conditions, ignore at least two important considerations: thermally-driven advection ('soil breathing'), in which daily heating at the soil surface cyclically alters the density of the gas phase and so drives advection of soil air, and wettability, which controls both the height of capillary rise and the area of the air-water interface. We propose to conduct detailed experiments measuring heat and water in both sealed and open soil columns. Our experiments will use the new thermo-TDR probe, capable of measuring temperature, thermal properties, and water content, allowing us to conduct several months of experiments on each individual soil column. This permits us to subject each soil column to a wide range of boundary conditions, and so to collect data for both calibration and validation from each soil column. We will examine effects of soil texture and wettability, water content, mean temperature, direction of thermal gradient, and influence of fluctuating boundary conditions on coupled heat and water movement in sealed soil columns. We will then study effects of soil texture and wettability, mean temperature, upper boundary condition, and advective vapor barrier on evaporation from open soil columns. In parallel with the laboratory experiments, we will develop a network model of coupled heat and water transfer in soils. A network model operates from first principles, and (in contrast with conventional continuum models) properties such as unsaturated hydraulic conductivity, air/water interfacial area, and soil breathing emerge from the network rather than being explicitly programmed in. This fundamental approach will allow us to examine which properties and processes are important under which conditions, furthering our understanding and focusing the development of improved continuum models in the future.This project will develop and disseminate new models and approaches in both experiment and modeling. These ideas, data, and models will be made available in the peer-ed literature, at conferences, and on a group website. Additionally, the research will be integrated into broader programs and activities of national interest, such as natural resource management and climate change.

0337553跨土壤表面的热量和水很大程度上驱动了大气和陆地水圈。 在近地表土壤中，热量和水的耦合传递是规则而不是例外，但耦合过程却鲜为人知。 实际上，使用事实上的标准菲利普和de Vries型耦合转移模型做出的预测可以大大关闭。 目前的模型基于仅涵盖狭窄条件的数据集，至少忽略了两个重要的考虑因素：热驱动的对流（“土壤呼吸”），在这种情况下，每天在土壤表面上进行每日加热，循环地循环地改变了气相的密度，因此可以使空气的对流和润滑性的高度促进毛细血管的高度，从而控制了这两种面积的高度和空中界面的高度。我们建议进行详细的实验，以测量密封和开放土壤柱中的热量和水。 我们的实验将使用新的Thermo-TDR探针，能够测量温度，热性能和水含量，从而使我们能够在每个土壤柱上进行几个月的实验。 这使我们可以使每个土壤柱处于各种边界条件上，因此从每个土壤柱中收集数据以进行校准和验证。 我们将检查土壤质地和润湿性，水含量，平均温度，热梯度的方向以及波动边界条件对密封土壤柱中耦合热和水运动的影响。 然后，我们将研究土壤质地和润湿性，平均温度，上边界条件和对流蒸气屏障对开放土壤柱蒸发的影响。与实验室实验并联，我们将开发一个网络模型，以耦合热和水中的水转移。 网络模型由第一原则和（与常规连续模型相反）属性，例如不饱和的水力传导率，空气/水界面区域以及从网络中出现的土壤呼吸出现，而不是明确编程。在实验和建模中传播新的模型和方法。 这些想法，数据和模型将在同行文献，会议和小组网站上提供。 此外，该研究将纳入更广泛的国家利益计划和活动，例如自然资源管理和气候变化。