Linear and nonlinear unified fluid flow in fractured porous media considering flow pattern adaptive conversions

Linear and nonlinear fluid flow in fractured rock masses often co-occurs because of the hydraulic pressure gradient discrepancy and significant permeability difference between fractures and rock matrixes. In the current Darcy-Forchheimer coupled theory, the linear and nonlinear fluid flow is often artificially and strictly confined to rock matrixes and fractures, respectively. In this study, we conducted a numerical study on linear and nonlinear unified fluid flow in fractured porous media, considering flow pattern adaptive conversions instead of artificial constraints. The flow pattern adaptive conversion is realized by a conversion factor of linear and nonlinear fluid flow. A numerical linear and nonlinear unified fluid flow method was proposed using the unified pipe-network method. The accuracy and correctness of the proposed method were validated by comparing it with the result of both linear and nonlinear fluid flow. This method can effectively describe the linear and nonlinear mixed fluid flow and calculate the distributions of linear and nonlinear flow regions in fractured porous media. Characteristics of the unified fluid flow in fractured porous media were analyzed in detail by parametric discussions based on the developed numerical method.