Effect of roughness on water flow through a synthetic single rough fracture |
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Authors: | Zhou Chen Jiazhong Qian Hongbin Zhan Zhifang Zhou Jinguo Wang Yefei Tan |
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Institution: | 1.School of Earth Sciences and Engineering,Hohai University,Nanjing,People’s Republic of China;2.School of Resources and Environmental Engineering,Hefei University of Technology,Hefei,People’s Republic of China;3.Department of Geology and Geophysics,Texas A&M University,College Station,USA;4.Nanjing Hydraulic Research Institute,Nanjing,People’s Republic of China |
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Abstract: | A single fracture is usually idealized theoretically as smooth parallel plates, but the real fractures are rough-walled with points of contact. Though relative roughness is considered in quantifying the flow through a single rough fracture (SRF) previously, additional factors such as the distribution of rough elements and bending degree of streamlines should be considered in order to obtain more accurate results. Semiempirical friction factor (f) and discharge per unit width (q) equations are first deduced taking relative roughness, roughness elements distribution and streamline reattachment length into consideration. A horizontal SRF model was then set up and a series of experiments and simulations were performed. Main conclusions are drawn: Recirculation of streamlines arises in the rough element and the intensity of the recirculation increases with the angle from which the streamlines enter into the rough elements and Reynolds number (Re); streamlines are discontinuously distributed when asperity height is large and nonlinear flow occurs; the nonlinearity of the flow increases with the increasing the asperity height and Re; the critical value of related roughness used to judge whether the influence of roughness on water flow through a SRF can be ignored or not should be much lower than 0.033; the revised f and q equations under laminar flow through a SRF are proved to be better when calculating the f and q values. |
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