Document Type : Article
Authors
1
Dept. of Mining & Metallurgical Engineering\r\nAmi&zwnj
2
Dept. of Mining & Metallurgical Engineering Ami
3
Dept. of Mining & Metallurgical Engineering \r\nAmi&
4
Dept. of Mechanical Engineering Amirkabir Univ&zwnj
Abstract
Fluid flow and solute transport in a fractured rock mass are of key interest for many practical applications, such as in the hydrocarbon and water industries and in the safe design of disposal sites for domestic, industrial and nuclear waste. In many geological structures, rock fractures are the main flow paths and are a most important attribute in rock mass hydraulic behavior. Therefore, the development of realistic and robust predictive models of flow and transport requires a thorough understanding of the physical processes that govern flow in individual fractures. The objective of this paper is to examine the impacts of fracture roughness on the flow velocity field throughout an individual fracture. First, a three-dimensional geometrical domain of an arbitrary rough-walled fracture, consisting of 150 volumetric elements (fracture segments) in 6 rows and 25 columns, was generated. The computational domain of this fracture was generated, and turbulent flow through the void specimen was simulated by using the finite volume method for a wide range of inlet velocities; from 0.01 to 1 m/s. In order to evaluate the effect of surface roughness and aperture on the average flow velocity, sixty-four horizontal sections, with 0.01mm consecutive distances in a z-direction and eleven vertical sections, normal to the y-direction and perpendicular to the main flow direction, with 1 mm consecutive distances in the y-direction, were considered through the geometrical domain, respectively. The average velocity on these horizontal and vertical sections has been normalized with the inlet velocity. These normalized velocities were used to illustrate roughness and aperture effects on flow velocity fields in rock fractures. The maximum value of the normalized velocity on horizontal sections is about 1.47, occurred in the inlet velocity of 0.01 m/s, which is close to the ideal magnitude for cubic law. By increasing inlet velocity, the maximum value of the normalized velocity on horizontal sections decreases from 1.47 to 1.34 for the inlet velocity of 0.01 m/s to 1 m/s, respectively. Moreover, by increasing inlet velocity, the corresponding height of the maximum value of the normalized velocity decreases from 0.205 mm to 0.18 mm for the inlet velocity of 0.01 m /s to 1 m/s, respectively. The results show that; (i) by increasing flow rate, the symmetry of the velocity profile decreases and inclines to the smoothest fracture surface, and, also, the intensity of the rotational flow increases, (ii) in high flow rates, the arrangement of flow channels changes and lower flow rates take place through large apertures.
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