Characterization of Flow under Different Geometric Properties and Reynold Numbers in Y-Junction Bifurcated Fractures

Abstract

Bifurcated fractures are the basic units of fracture networks. In this paper, a bifurcated fracture model is designed using Fluent software to characterize the fluid flow in a fracture network. The characterization of water flow was investigated by changing the geometrical properties, namely, joint roughness coefficient (JRC), angle between two outlet fractures (θ), and the mechanical aperture (e) of either outlet fracture. The effect of Reynolds numbers (Re), hydraulic gradient (J), flow rate (Q), flow velocity (V), critical Reynolds numbers (Rec), and hydraulic aperture (E) on the flow were systematically analyzed. The results showed that (1) given the increase in roughness and θ, the flow ratio in the branches increases nonlinearly, whereas the aperture ratio showed an opposite characteristic; (2) the deflected flow caused by the variation in θ is mainly attributed to inertial forces, whereas that caused by the change in JRC and the aperture ratio is due to the combination of the viscous and inertial forces; (3) when Re was small, the ratio of E·e−1 was slightly lower than 1, and with an increase in Re, the E·e−1 strength of the outlet fractures was weak; and (4) the aperture is the most important parameter affecting the deflected flow, followed by θ and JRC.