scholarly journals Constitutive Relations for Unsaturated Flow in a Fracture Network

2001 ◽  
Author(s):  
H. H. Liu ◽  
G. S. Bodvarsson
Keyword(s):  
Unsaturated Flow ◽  
Constitutive Relations ◽  
Fracture Network

scholarly journals Constitutive relations for unsaturated flow in a fracture network

2001 ◽  
Vol 252 (1-4) ◽  
pp. 116-125 ◽  
Author(s):  
Hui-Hai Liu ◽  
Gudmundur S. Bodvarsson
Keyword(s):  
Unsaturated Flow ◽  
Constitutive Relations ◽  
Fracture Network

Dual-Permeability Modeling of Capillary Diversion and Drift Shadow Effects in Unsaturated Fractured Rock

2009 ◽  
Vol 131 (10) ◽  
Author(s):  
Clifford K. Ho ◽  
Bill W. Arnold ◽  
Susan J. Altman
Keyword(s):  
Fractured Rock ◽  
Constitutive Relations ◽  
Water Flux ◽  
Fracture Network ◽  
Small Scale ◽  
Grid Refinement ◽  
Capillary Pressures ◽  
And Behavior ◽  
Capillary Pressure Curves ◽  
The Impact

The drift-shadow effect describes capillary diversion of water flow around a drift or cavity in porous or fractured rock, resulting in lower water flux directly beneath the cavity. This paper presents computational simulations of drift-shadow experiments using dual-permeability models, similar to the models used for performance assessment analyses of flow and seepage in unsaturated fractured tuff at Yucca Mountain. Comparisons were made between the simulations and experimental data from small-scale drift-shadow tests. Results showed that the dual-permeability models captured the salient trends and behavior observed in the experiments, but constitutive relations (e.g., fracture capillary-pressure curves) can significantly affect the simulated results. Lower water flux beneath the drift was observed in both the simulations and tests, and fingerlike flow patterns were seen to exist with lower simulated capillary pressures. The dual-permeability models used in this analysis were capable of simulating these processes. However, features such as irregularities along the top of the drift (e.g., from roof collapse) and heterogeneities in the fracture network may reduce the impact of capillary diversion and drift shadow. An evaluation of different meshes showed that at the grid refinement used, a comparison between orthogonal and unstructured meshes did not result in large differences.

Influence of local splitting behavior at intersections on infiltration in an unsaturated fracture network 

2021 ◽  
Author(s):  
Song Xue ◽  
Zhibing Yang ◽  
Yi-Feng Chen
Keyword(s):  
Large Scale ◽  
Preferential Flow ◽  
Unsaturated Flow ◽  
Flow Characteristics ◽  
Fracture Network ◽  
Liquid Volume ◽  
Complex Flow ◽  
Local Flow ◽  
Divergent Flow ◽  
Macro Scale

<p>Understanding and predicting the macro-scale flow characteristics in the fractured vadose zone is of great importance for subsurface hydrological applications. Here we develop a network model to study infiltration in unsaturated fracture networks. We consider an idealized honeycomb-like fracture network composed of a series of Y-shaped and inverted Y-shaped intersections. At the scale of intersections, liquid storage/release and splitting/convergence behaviors are modeled according to local splitting relationships obtained from detailed laboratory work and numerical simulations. By varying the splitting relationships, the influence of local flow behaviors on large scale flow structures is systematically investigated. We find that when the water split tends to split equally at the intersection, a divergent flow structure forms in the network. Conversely, unequal splitting leads to preferential pathways. We also find that an avalanche infiltration mode, i.e., sudden release of a large amount of water from the network, emerges spontaneously, and is modulated by the local splitting behavior. The pathways of preferential flow is controlled by the liquid volume triggered by avalanches and the network structure. The improved understanding from this study may shed new light on the complex flow dynamics for unsaturated flow in fractured media.</p>

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