Effect of Shearing on Non-Darcian Fluid Flow Characteristics through Rough-Walled Fracture

Biao Li,Jianrong Xu,Wei-Chau Xie,Weiya Xu,Long Yan,Mingjie He

doi:10.3390/w12113260

Abstract

The heterogeneous fracture geometry induced by the presence of roughness and shearing complicates the fracture flow. This paper presents a numerical investigation of the non-Darcian flow characteristics of rough-walled fractures during shear processes. A series of fracture flow simulations were performed on four types of fractures with different joint roughness coefficients (JRCs), and the different shear displacements were imitated by degrees of mismatch on two fracture surfaces. The results show that the disorder of fracture geometries and the increase in flow rate are the main causes for the emergence of an eddy flow region, which can significantly reduce the fracture conductivity and change the fracture flow from linear to nonlinear. The Forchheimer equation provides a good model for the nonlinear relationship between the hydraulic gradient and the flow rate in the fracture flow. When the shear displacement or JRC increased, the linear permeability coefficient kv decreased, while the nonlinear coefficient β increased. A three-parameter equation of β was used to examine the inertial effect induced by the fracture roughness JRC and the variation coefficient of aperture distribution σs/em. The critical Reynolds number was a combined effect of aperture, viscous permeability, and inertial resistance, assuming the flow becomes non-Darcian when the inertial part is greater than 10%.

Highlights

The fluid flow processes in fractured aquifers are of great importance in many engineering practices, such as water flow in dam foundation, underground mining extraction, enhanced geothermal systems, and fluid waste disposal
Eddy flow occurred with an increase in the Reynolds number due to the local effects of sharp-cornered asperities, which enhanced the tortuosity by changing local flow direction
The results showed that increasing the and shear displacement resulted in a high characteristics

Summary

Introduction

The fluid flow processes in fractured aquifers are of great importance in many engineering practices, such as water flow in dam foundation, underground mining extraction, enhanced geothermal systems, and fluid waste disposal. The inertial losses cannot be neglected with regard to viscous forces arising from changes in flow flux or direction and localized eddy formation [4,5]. In this case, the pressure drops more than the proportional increase in the flow velocity; this is known as the non-Darcian fluid flow. The pressure drops more than the proportional increase in the flow velocity; this is known as the non-Darcian fluid flow To describe such viscous and inertial losses, the Forchheimer equation is widely used [6,7,8]

Methods

Results

Conclusion