Numerical models porous-fracturing

Traditionally, the use of analytical models in environmental tracer studies has been far more widespread than numerical models. There are a number of reasons for this. Analytical models are easier to use and manipulate than numerical ones they require less hydrodynamic information and/or field data and the time required to build a transport model is much less than for a numerical model. Multiple examples of such models can be found in the literature for various tracers H, He, C, and C1 (e.g., Castro et al., 2000 Nolte et al., 1991 Schlosser et al., 1989 Solomon et al., 1996 Stute et al., 1992b Torgersen and Ivey, 1985). Generally, these models are either applied to a single aquifer in porous or fractured media or to one particular area within the aquifer such as recharge or discharge areas. 

NUMERICAL FLOW AND HEAT TRANSFER MODEL OF THE POROUS-FRACTURING HYDROTHERMAL SYSTEM OF THE PARATOON THERMAL WATER HELD... 

In case of nonequilibrium reactions, the same effect can be obtained as above when different transfer rate coefficients are assumed, as we see in Fig. 6.14. Numerical modelling of the decay chain reactions in fractured porous media with a nonequilibrium sorption model is treated for the first time. Further there exists no analytical solution for this type of model. 

A new numerical solver RF-RTM for the reactive transport in fractured porous media was investigated. The simulator RF-RTM is a three-dimensional model, that can consider several nonequilibrium kinetic type models. This paper illustrates the accuracy with the finite element model for simulating decay reactions in fractured porous media. The presented results show the capability of RF-RTM to simulate transport of one or more species. The finite element model RF-RTM was verified for several situations when sorption occurs imder equilibrium conditions such as in Example 1 and 5, or in case of matrix diffusion such as in Example 4. Validation of the nonequilibrium model was shown in Example 3. The nonequilibrium model is verified only for homogenous media. Numerical modelling of the decay chain reactions in fractured porous media with a nonequilibrimn sorption model is treated for the first time. Especially the different penetrations of decay chain components in a fiacture-matrix system was illustrated through a series of simulations (see Example 6). Further research is needed to quantify the effect of nonlinear sorption in the migration of the contaminants with sequentially deca3ong processes in fractured porous media. 

Di Pietro, L. 1996. Application of a lattice gas numerical algorithm to modelling water transport in fractured porous media. Transp. Por. Media 22 307-325. 

Mathematical models and numerical methods for the coupled processes of fractured rock masses, soils and general porous media... 

The establishment of mathematical models (including the governing equations of coupled processes and constitutive models) and numerical methods for the solutions of practical problems attracted extensive attention in this area since mid 1990 s. Both equivalent continuum approach and discrete fracture system approach are used, with focus on coupled T-H, H-M, M-H-C and T-H-M processes of fractured rocks, soils and general porous media. Summarized below are some of the representative works ... 

Over the past two decades AECL has developed a three-dimensional code, MOTIF (Model Of Transport In Fractured/porous media), for detailed modelling of groundwater flow, heat transport, mechanical equilibrium and solute transport in a fractured rock mass. The initial development was completed in 1985 (Guvanasen 1985). Since then the code has undergone extensive updating, verification - comparison with known analytical or numerical solutions - and validation - comparison with experiments - (Chan et al. 2(XX)). In the latter document sixteen test cases were repotted to verify the code for groundwater flow, heat transfer and solute transport in fractured or porous rock. In this paper, additional verification and validation studies with an emphasis on thermo-hydromechanical (T-H-M) processes are presented. 

Bai, M. and Roegiers, J.C. 1994. Fluid flow and heat flow in deformable fractured porous media. Int. J. Engng Sci. 32(10) pp. 1615-1633. Callari C. Federico F. 2000. FEM validation of a double porosity elastic model for consolidation of structurally complex clayey soils. Int. J. Numer. Analy. Meth. 24 (4) pp. 367-402. 

The following examples illustrate the variety of geochemical problems treated with the numerical simulator. We first consider geochemical processes in porous media nitrification (Example 1), validation of the nonequilibrium model (Example 2) and TCE transformation (Example 3). After that we treat the same problems in fractured porous media matrix diffusion (Example 4), two-member decay chain (Example 5). Finally, Example 5 is extended to demonstrate the influence of parameter variation for the concentration distribution that occurs either under equilibrium or nonequilibriiun conditions (Example 6). 

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