Process-based characterization of flow in unsaturated fractured rocks

由于过程理解、尺度效应和跨尺度过程参数表征等诸多不确定性，模拟非饱和裂隙岩石的快速流动仍然是一个挑战。我们的建议侧重于开发一种模拟局部尺度非饱和流动的建模工具，并评估小尺度过程在多大程度上影响非饱和裂隙岩石中水在大尺度上的走时分布。模型开发的主要目标是模拟自由表面流动，包括表面张力和接触线动力学的影响。为此，将开发无网格平滑粒子流体力学（SPH）代码。为了了解裂缝表面的流动过程，模拟将涵盖广泛的流动形式和相互作用，包括：(1)毛细管流动，(2)裂缝表面的薄吸附膜，(3)裂缝中的高度非线性流动形式，例如液滴流动。对这些流动区室之间复杂的水动力相互作用进行建模，将极大地增强对水通过裂隙非饱和岩石材料的走时分布的理解，这是Richards方程等常用体积有效连续体建模方法无法捕捉到的。所开发的基于颗粒的流动模型将提供一个通用的数值框架来研究通过各种多孔材料和与固结岩石相关的裂缝几何形状的非饱和流动。

Simulation of rapid flow through unsaturated fractured rocks is still a challenge because of a number of uncertainties ranging from process understanding, scale effects and characterization of process parameters across scales. Our proposal focuses on the development of a modeling tool for simulation of unsaturated flow on a local scale and the assessment in how far small scale processes affect travel time distribution of water in unsaturated fractured rocks on larger scales. The main objective of model development is the simulation of free-surface flow including the effects of surface tension and contact line dynamics. For this purpose, meshless Smoothed Particle Hydrodynamics (SPH) codes will be developed. To obtain an understanding of flow processes that occur on fracture surfaces, simulations will cover a broad spectrum of flow regimes and interactions ranging from: (1) capillary flow, (2) thin adsorbed films on fracture surfaces, and (3) highly non-linear flow regimes in fractures, e.g. droplet flow. Modeling the complex hydrodynamic interplay between these flow compartments will strongly enhance the understanding of travel time distributions of water through fractured unsaturated rock materials, which cannot be captured with common volume effective continuum modeling approaches such as the Richards equation. The developed particle based flow models will provide a versatile numerical framework to investigate unsaturated flow through various porous materials and fracture geometries associated with consolidated rocks.