A new geometrical model for non-linear fluid flow through rough fractures

Abstract

Summary Fractures in rock mass are the main flow paths and introduce as a most important attribute in rock mass hydraulic behavior. The non-linear fluid flow through rock fractures was studied in this paper. Computational domain of an artificial three-dimensional fracture is generated and used for CFD simulations. Both laminar and turbulent flow simulations were performed for a wide range of flow rates. Also, a new non-linear fluid flow formulation was developed on the basis of some geometrical and kinematical assumptions for fracture and fluid flow, respectively. Based on comparison between simulation results and developed formulation, a new geometrical model has been proposed for non-linear fluid flow through rough fractures, which suggests a polynomial expression, like Forchheimer law, to describe the dependence of pressure drop on flow rate. Finally, this model has been evaluated with experimental results of a fracture with different geometries. The results show that the predicted pressure drop for turbulent flow simulation was roughly 3–17% more than those for laminar one at the Reynolds number of 4.5–89.5, respectively. Moreover, a good accuracy was found between the proposed model and turbulent flow simulation results. These findings may prove useful for computational studies of flows through real rock fractures, or inclusions in simulators for large-scale flow in fractured rocks.