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Visualization and modeling of the evaporation process using representative 2D Micromodels and universal scaling laws

使用代表性的二维微模型和通用缩放定律对蒸发过程进行可视化和建模

基本信息

批准号：
318157347
负责人：
Professor Dr. Helmut Geistlinger
金额：
--
依托单位：
Department Bodensystemforschung
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2016
资助国家：
德国
起止时间：
2015-12-31 至 2020-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/318157347?language=en
关键词：
Visualization modeling evaporation process using

项目摘要

Evaporation is a key process controlling the soil water budget and is characterized by a complex interplay of atmospheric boundary conditions and the flow- and transport properties of the 3-phase system "solid phase - water - gas". The central objective is the experimental and theoretical investigation of the evaporation process for real soil structures using representative 2D-micromodels and network models. The 3D-pore structure is measured by micro-X-ray computer tomography (micro-CT) and mapped to the 2D-micromodel by a new topological 2D-3D transformation. The experimental results are compared with the theoretical results of an evaporation-network model, which for the first time takes into account the evaporation over the thick-film surface and the experimental pore size distribution. The 2D-micromodels have both an inner and an outer roughness as natural soils and loose rock. For the first time the thick-film flow is investigated as a function of the microstructure of the solid surface. Therefore, REV-micromodels (REV: representative elementary volume) are produced in silicon (inner roughness = 0.1 micro-m), glass (0.5) and glass ceramic (3). As a working hypothesis it is assumed that (i) different atmospheric conditions (diffusive flow, laminar flow and turbulent flow; increasing potential evaporation rate) cause different drying dynamics and that (ii) the critical water potential depends on the thick-film flow and on the thick-film-surface. Two soil types from agricultural land (Fuhrberger Feld) are investigated: (i) sandy soil (A-horizon) and (ii) medium sand (C-horizon). The pore structure is analyzed using micro-CT (maximal resolution: 5 micro-m) and methods of mathematical morphology (Minkowski functions). The micro-model experiments are carried out for both the horizontal and the vertical water flow in the range of relevant capillary numbers; (10^-7 ... 10^-4; increasing evaporation rate). The visualization experiments are carried out with two high-resolution SLR cameras (18 megapixels) and a fluorescence microscope. The Thick-film dynamics is described by the standard theory of "wetting on rough surfaces". For all experiments (i) a cluster analysis is conducted, (ii) the gravitational correlation length is calculated by universal scaling laws, and (iii) the fractal dimension of the drying/displacement front is determined. Based on a representative network model the two important parameters of the continuum theory (REV-scale) - the effective permeability and the effective diffusion coefficient - are derived. The expected results are both of fundamental interest and of great practical relevance, as they improve process understanding and consequently the predictive modeling of evaporation at REV-scale.

蒸发是控制土壤水分收支的关键过程，其特征在于大气边界条件与三相系统“固相-水-气”的流动和输运性质的复杂相互作用。中心目标是实验和理论研究的蒸发过程中的真实的土壤结构，使用代表性的二维微观模型和网络模型。三维孔隙结构的测量微X射线计算机断层扫描（micro-CT）和映射到二维微观模型的一个新的拓扑2D-3D变换。的蒸发网络模型，其中第一次考虑到在厚膜表面的蒸发和实验的孔径分布的理论结果与实验结果进行了比较。二维微观模型具有天然土壤和松散岩石的内部和外部粗糙度。第一次厚膜流动的固体表面的微观结构的函数进行了研究。因此，在硅（内部粗糙度= 0.1微米）、玻璃（0.5）和玻璃陶瓷（3）中产生REV-微模型（REV：代表性基本体积）。作为一个工作假设，它是假定（i）不同的大气条件（扩散流，层流和湍流;增加潜在的蒸发速率）导致不同的干燥动力学和（ii）的临界水势取决于厚膜流和厚膜表面。研究了两种农田土壤类型（Fuhrberger费尔德）：（i）桑迪土（A层）和（ii）中砂（C层）。使用显微CT（最大分辨率：5微米）和数学形态学方法（Minkowski函数）分析孔结构。在相应的毛管数范围内进行了水平和垂直水流的微观模型实验，10^-4;增加蒸发率）。可视化实验进行了两个高分辨率的单反相机（18万像素）和荧光显微镜。厚膜动力学是由“粗糙表面润湿”的标准理论描述的。对于所有的实验（i）进行聚类分析，（ii）的重力相关长度计算的通用标度律，和（iii）的分形维数的干燥/位移前确定。基于一个典型的网络模型，导出了连续介质理论（REV尺度）的两个重要参数--有效渗透率和有效扩散系数。预期的结果是根本利益和巨大的实际意义，因为它们提高了过程的理解，从而在REV规模的蒸发预测建模。