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.

蒸发是控制土壤预算的关键过程，其特征是大气边界条件的复杂相互作用以及3相系统“固相 - 水 - 气体”的流动和运输特性。核心目标是使用代表性的2D微型模型和网络模型对真实土壤结构的蒸发过程的实验和理论研究。 3D孔结构通过Micro-X射线计算机断层扫描（Micro-CT）测量，并通过新的拓扑2D-3D变换映射到2D-Micromodel。将实验结果与蒸发网络模型的理论结果进行了比较，该模型首次考虑了厚膜表面上的蒸发和实验性孔径分布。 2D微型模型既具有内在的粗糙和外部粗糙度，如天然土壤和松散的岩石。首次研究厚膜流是固体表面微观结构的函数。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-Micromodels（Rev：代表性基本体积）。作为一个工作假设，假定（i）不同的大气条件（扩散流动，层流和湍流；增加潜在的蒸发速率）会导致不同的干燥动力学，并且（ii）关键水电位取决于厚膜流量和厚膜厚膜的厚度。研究了两种来自农业土地（Fuhrberger Feld）的土壤类型：（i）沙质土壤（a-horizon）和（ii）中砂（C-Horizon）。使用Micro-CT（最大分辨率：5 micro-M）和数学形态学方法（Minkowski函数）分析孔结构。在相关毛细管数范围内，对水平和垂直水流进行了微模型实验。（10^-7 ... 10^-4；蒸发率提高）。可视化实验是使用两个高分辨率SLR相机（18兆像素）和一个荧光显微镜进行的。厚膜动力学由“在粗糙表面上润湿”的标准理论描述。对于所有实验（i）进行聚类分析，（ii）重力相关长度是通过通用缩放定律计算的，并且（iii）确定干燥/位移前面的分形维度。基于代表性网络模型，得出了连续理论的两个重要参数 - 得出了有效的渗透性和有效扩散系数。预期的结果既具有基本的兴趣，又具有极大的实际相关性，因为它们可以提高过程的理解，从而提高了Rev级蒸发的预测建模。