A Lattice Boltzmann Based Model for Predicting Unsaturated Flow through Soil Macropores and Capillary Pores

基于格子玻尔兹曼的预测土壤大孔和毛细孔不饱和流的模型

• 批准号: 1100020
• 负责人: Milind Khire
• 金额: $ 21.16万
• 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: 2011
• 资助国家: 美国
• 起止时间: 2011-04-01 至 2014-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1100020&HistoricalAwards=false
• 关键词: Lattice; Boltzmann; Based; Model; Predicting; Lattice; Boltzmann; Based; Model; Predicting

The key objective of this project is to couple the Richards Equation based unsaturated flow in capillary pores of soils with flow through macropores using the Navier-Stokes Equations solved using the Lattice-Boltzmann (LB) Method for two phase (liquid and gas) flow. Because computationally efficient mechanistically-based models do not exist, groundwater recharge, or deep drainage estimates, or gas emissions from landfills are often carried out by ignoring preferential flow or by modeling it empirically. Dual permeability models simulate macropore flow by specifying separate sets of unsaturated properties to the micro and macro pores. However, the flow through macropores does not follow Darcian flow and assumes all macropores are connected as a continuum while often macropores are discrete and disconnected. The central idea behind the model to be developed in this project is that flow through macropores is similar to flow in conduits having irregular shapes and hence Navier Stokes equations are more appropriate and are numerically stable when solved using the Lattice-Boltzmann method. With the advances in digital X-ray CT imaging techniques, it is now possible to have pore structure of soils characterized relatively quickly and economically. Hence, a model that can take advantage of such high resolution pore structure data can revolutionize the way we estimate long-term liquid percolation into landfills or gas emissions from landfills. The macro pore and micro pore structure in the soil system will be digitally input to the model using X-ray Computed Tomography (CT) image data for soil samples collected from instrumented field-scale clay caps to validate the modeling approach. High-resolution water balance data has been collected over a period of three years from two field-scale clay cap test sections located at a landfill in Detroit. The conventional physically-based numerical models can capture the unsaturated flow through capillary or micropores relatively accurately. However, they cannot model flow through macropores which are formed and continuously evolve due to inadequate compaction, desiccation cracking, freeze/thaw, root penetration, and rodent activity. The model that will be developed will overcome the challenge of modeling liquid or gas flow through macropores. A numerical model that takes advantage of recent advances in X-ray imagining of soil structure for modeling flow through soils will provide practitioners and regulators a tool to accurately predict long-term deep drainage into ground water systems of environmental significance or green-house gas emissions from landfills. A course module on migration of liquids and gases from waste sites will be prepared for an undergraduate landfill design class and a course module containing theory and lab experimentation to demonstrate preferential flow through soils will be prepared and introduced in a graduate level course. Outreach to high school students during summer training camps will carried out with hands-on demonstrations at Michigan State University.

该项目的关键目的是将基于Richards方程的不饱和流在土壤的毛细管毛孔中，并使用使用晶状体螺栓曼（LB）方法求解的Navier-Stokes方程，用于两相（液体和气体）。 由于不存在基于计算有效的机械模型，因此通常通过忽略优先流量或通过经验对垃圾填埋场进行垃圾填埋场的气体发射，或者垃圾填埋场的气体排放。 双渗透率模型通过将单独的不饱和特性集指定给微孔和宏孔，从而模拟大孔流。 但是，通过大孔的流量不遵循Darcian流动，并假设所有大孔都以连续体连接，而大孔通常是离散和断开连接的。 在该项目中要开发的模型背后的核心思想是，通过大孔的流动与具有不规则形状的导管中的流动相似，因此使用lattice-boltzmann方法求解时，Navier Stokes方程更合适，并且在数值上稳定。 随着数字X射线CT成像技术的进步，现在有可能在相对和经济上具有相对和经济的孔结构。 因此，可以利用如此高分辨率的孔结构数据的模型可以改变我们估计垃圾填埋场中的长期液体渗透或气体排放的方式。 土壤系统中的宏孔和微孔结构将使用X射线计算机断层扫描（CT）图像数据将来自仪器田间尺度粘土帽收集的土壤样品进行数字输入，以验证建模方法。 从位于底特律垃圾填埋场的两个现场尺度粘土帽测试部分，已经收集了三年的高分辨率水平衡数据。常规的基于物理的数值模型可以相对准确地捕获穿过毛细管或微孔的不饱和流。 但是，由于压实不足，干燥裂纹，冻结/融化，根穿透和啮齿动物活性，它们无法模拟流过大孔和不断发展的大孔。 将要开发的模型将克服建模通过大孔的液体或气体流量的挑战。一个数值模型，利用X射线对土壤进行建模的土壤结构的最新进展将为从业者和调节器提供一种工具，以准确预测具有环境意义的地下水系统或垃圾填埋场中的绿色房屋气体排放的长期深层排水。 将准备有关液体和气体从废物站点迁移的课程模块，为本科垃圾填埋场设计类别准备，并在研究生水平的课程中准备并引入一个包含理论和实验室实验的课程模块，以证明通过土壤的优先流通。在夏季训练营期间，将向高中生举行宣传，将在密歇根州立大学举行动手演示。