Seepage disturbance mechanism and interface force of cylindrical barrier in fracture

Abstract

The fluid flow in the crack is disturbed by the contact area. The parallel-plate model with a circular cylindrical contact area is regarded as an idealization of the real contact fracture, and a computational fluid dynamics simulation is performed on it to analyze the interaction between the contact area and the flow around it. The size of the contact area controls the disturbance intensity to the flow velocity magnitude and the disturbance range to the velocity direction. Due to the existence of viscosity, the flow near the wall has a larger shear rate. The intermediate transition region is located between the contact area and the fracture lateral wall and does not contain the region with strong viscous friction caused by the wall. The flow velocity magnitude in the intermediate transition zone changes exponentially in space and has a peak value near the contact area. After the flow bypasses the contact area, the inertial effect caused by the increase in flow velocity magnitude in the local flow channel controls the generation and development of the low-velocity region and the asymmetric degree of the velocity direction distribution. Both the mechanical aperture and the inlet flow velocity affect the stress distribution on the surface of the contact area. The occurrence of the nonlinear flow behavior of fracture seepage and nonlinear change trend of logarithmic drag coefficient curve can be predicted with the same critical Reynolds number. These results provide a useful guide for further exploring the local flow and the surface stress distribution of the local interior geometric property in a single rough-walled fracture on the mesoscopic scale.