Collaborative Research: Experimental and Numerical Characterization of Thin Films in Three-Dimensional Porous Media

现有的对多孔域薄膜特性的分析往往是建立在二维或准三维几何上简单的孔隙结构上，而没有明确考虑三维孔隙的连通性。需要更深入的数值和实验研究来弥补二维和三维实验分析之间的差距，以及颗粒状多孔介质中孔尺度薄膜特性的三维数值和实验分析之间的差距。因此，我们提出的研究建立在我们正在进行的孔隙尺度界面研究的基础上，旨在将实验和数值分析结合起来，以便更好地理解由相互连接的任意粗壁孔隙几何形状组成的三维多孔介质中的薄膜特性和热力学。在这个为期1年的扩展提案中，我们的目标是开发一个基于热力学声音自由能的多相晶格-玻尔兹曼模型（可以处理高密度对比的流体并实现热力学声音固-流相互作用）。为了获得模型验证的数据，我们将测量与火山凝灰岩破碎中薄膜形成和分布有关的薄膜特征。这包括成像水的分布，因为它们从吸附膜到毛细管保持水随着蒸汽压力的增加。根据图像，可以估计发生毛细凝结的临界分离距离。薄膜特性将首先使用延时数字显微镜在几何简单的二维流道中测量，随后使用计算机微断层扫描（CMT）在破碎的凝灰岩样品中测量更复杂的三维系统。从CMT图像中，我们将确定用于验证新模型开发的毛细管凝聚区域的位置和范围。一旦使用二维实验数据验证了模型，该模型将用于模拟具有水力连接任意孔隙几何形状的三维天然多孔介质中的薄膜形成和分布。数值模拟结果的几何形状和范围的毛细血管凝聚区将与微层析成像数据进行比较。然后，数值模型将用于绘制无法通过实验测量的变量的空间分布，如流体密度、薄膜中的蒸气压、界面宽度和三维曲率，从而计算界面能、表面张力、化学势和分离压力。拟议研究的更广泛影响：我们期望拟议研究的结果可以在不同领域产生重要的更广泛的影响，其中与低饱和度状态相关的过程具有重要意义，包括干旱区灌溉和水管理，渗透区污染物和胶体颗粒的命运和运输，非常干燥气候下的核废料处理，提高石油采收率，以及行星科学。此外，该项目将为本科生和研究生以及博士后提供培训。

0610108/0610003Wildenschild/Schaap Existing analyses on thin film characteristics in porous domains are often built on two- orquasi-three dimensional geometrically simple pore structures without explicitlyaccommodating pore connectivity in the third dimension. More in-depth numerical andexperimental studies are needed to bridge the gap between two- and three dimensionalexperimental analyses as well as the gap between three-dimensional numerical andexperimental analyses of pore-scale thin-film characteristics in granular porous media.Hence, the proposed research, which builds on our ongoing pore-scale interfacialresearch, aims at integrating experimental and numerical analyses for betterunderstanding of thin film characteristics and thermodynamics in three-dimensionalporous media consisting of interconnected arbitrary rough-walled pore geometries.In this 1-year extension proposal, we aim to develop a thermodynamically soundfree-energy-based multiphase lattice-Boltzmann model (that can handle fluids with highdensitycontrasts and implements thermodynamically-sound solid-fluid interactions). Toobtain data for model verification, we will measure thin film characteristics related tofilm formation and distribution in a crushed volcanic tuff. This includes imaging waterdistributions as they progress from adsorbed films to capillary held water with increasingvapor pressure. Based on the images it is possible to estimate the critical separationdistance at which capillary condensation takes place. The film characteristics will first bemeasured in geometrically simple two-dimensional flow channels using time-lapse digitalmicroscopy, and subsequently using computerized microtomography (CMT) for morecomplex three-dimensional systems in crushed tuff samples. From the CMT images wewill determine the location and the extent of the capillary condensed regions to be used tovalidate new model developments.Once the model is validated using the two-dimensional experimental data, themodel will be used to simulate thin film formation and distributions in a threedimensionalnatural porous medium with hydraulically connected arbitrary poregeometries. Numerically simulated results on the geometry and extent of capillarycondensed zones will be compared to the microtomography data. The numerical modelwill then be used to map the spatial distribution of variables that cannot be measuredexperimentally such as fluid density, vapor pressure in thin films, interfacial width, andthree-dimensional curvatures, to subsequently calculate interfacial energies, surfacetension, chemical potentials, and disjoining pressures.Broader Impacts of the proposed research:We expect that the findings from the proposed research could have importantwider impacts in diverse fields where processes relevant to the low saturation regime areof significance, including arid zone irrigation and water management, fate and transportof contaminants and colloidal particles in the vadose zone, nuclear waste disposal in verydry climates, enhanced oil recovery, and in planetary sciences. In addition, the projectwill provide training for undergraduate and graduate students, as well as a post-doc.