Accurate descriptions of matrix diffusion across the fracture/matrix interface are critical to assessing contaminant migration in fractured media. The classical transfer probability method is only applicable for relat...Accurate descriptions of matrix diffusion across the fracture/matrix interface are critical to assessing contaminant migration in fractured media. The classical transfer probability method is only applicable for relatively large diffusion coefficients and small fracture spacings, due to an intrinsic assumption of an equilibrium concentration profile in the matrix blocks. Motivated and required by practical applications, we propose a direct numerical simulation （DNS） approach without any empirical assumptions. A three-step Lagrangian algorithm was developed and validated to directly track the particle dynamics across the fracture/matrix interface, where particle＇s diffusive displacement across the discontinuity is controlled by an analytical, one-side reflection probability. Numerical experiments show that the DNS approach is especially efficient for small diffusion coefficients and large fracture spacings, alleviating limitations of the classical modeling approach.展开更多
Non-Darcian flow has been well documented for fractured media,while the potential non-Darcian flow and its driven factors in field-scale discrete fracture networks(DFNs)remain obscure.This study conducts Monte Carlo s...Non-Darcian flow has been well documented for fractured media,while the potential non-Darcian flow and its driven factors in field-scale discrete fracture networks(DFNs)remain obscure.This study conducts Monte Carlo simulations of water flow through DFNs to identify non-Darcian flow and non-Fickian pressure propagation in field-scale DFNs,by adjusting fracture density,matrix hydraulic conductivity,and the general hydraulic gradient.Numerical simulations and analyses show that interactions of the fracture architecture with the hydraulic gradient affect non-Darcian flow in DFNs,by generating and adjusting complex pathways for water.The fracture density affects significantly the propagation of hydraulic head/pressure in the DFN,likely due to fracture connectivity and flow channeling.The non-Darcian flow pattern may not be directly correlated to the non-Fickian pressure propagation process in the regional-scale DFNs,because they refer to different states of water flow and their controlling factors may not be the same.Findings of this study improve our understanding of the nature of flow in DFNs.展开更多
基金supported by the United States Department of Energythe Desert Research Institute IR&D Funds
文摘Accurate descriptions of matrix diffusion across the fracture/matrix interface are critical to assessing contaminant migration in fractured media. The classical transfer probability method is only applicable for relatively large diffusion coefficients and small fracture spacings, due to an intrinsic assumption of an equilibrium concentration profile in the matrix blocks. Motivated and required by practical applications, we propose a direct numerical simulation （DNS） approach without any empirical assumptions. A three-step Lagrangian algorithm was developed and validated to directly track the particle dynamics across the fracture/matrix interface, where particle＇s diffusive displacement across the discontinuity is controlled by an analytical, one-side reflection probability. Numerical experiments show that the DNS approach is especially efficient for small diffusion coefficients and large fracture spacings, alleviating limitations of the classical modeling approach.
基金funded partially by the National Natural Science Foundation of China under grants 41628202,41330632 and 11572112.
文摘Non-Darcian flow has been well documented for fractured media,while the potential non-Darcian flow and its driven factors in field-scale discrete fracture networks(DFNs)remain obscure.This study conducts Monte Carlo simulations of water flow through DFNs to identify non-Darcian flow and non-Fickian pressure propagation in field-scale DFNs,by adjusting fracture density,matrix hydraulic conductivity,and the general hydraulic gradient.Numerical simulations and analyses show that interactions of the fracture architecture with the hydraulic gradient affect non-Darcian flow in DFNs,by generating and adjusting complex pathways for water.The fracture density affects significantly the propagation of hydraulic head/pressure in the DFN,likely due to fracture connectivity and flow channeling.The non-Darcian flow pattern may not be directly correlated to the non-Fickian pressure propagation process in the regional-scale DFNs,because they refer to different states of water flow and their controlling factors may not be the same.Findings of this study improve our understanding of the nature of flow in DFNs.
