Computer Simulation of Fluid Flow in a Single Fracture with "In-Plane Heterogeneity" Considered

Muraoka, Tamotsu*; Sato, Seiji*; Yamamoto, Asao*; Yatake, Yoichi*; Asano, Rinichi*; Yamamoto, Ryuichi*

The heterogeneity of the transmissivity and aperture in a single fracture, so called "in-plane heterogeneity", is considered to have an effect on the migration of radionuclides in a host rock of geological disposal of nuclear wastes. Aiming at better understanding of this effect for the safety assessment of geological disposal, we have improved the computer simulation code for the 3D flow and transport analysis in a single fracture developed in 2002 using the lattice Gas Automaton (LGA) method, and we have conducted the various flow and transport simulations using the 3D fracture models. Upon the improvement of the LGA code, we have investigated the macroscopic averaging method for the pseudo-4D face-centered-hypercubic (FCHC) model of 3D LGA simulation to come up with relation to map the numerical results of the LGA code onto real physical quantities such as pressure and velocity. Furthermore, we have improved the usability of the LGA code and its computational efficiency by algorithm tuning and parallel processing. We have also surveyed the results of the previous research on the in-plane heterogeneity of single fractures, examined the parameters to describe the heterogeneity, and obtained the 3D mathmatical model by S.R. Brown and P.W.J. Glover to create fractally rough synthetic fractures with these parameters reproduced well. Based on the above results, we have conducted the 3D simulations of fluid flow and mass transport in various numerically synthesized fractures. Finally, we have evaluated the effects of the parameters describing the in-plane heterogeneity on the property of fluid flow and mass transport through single fractures.