Journal cover Journal topic
Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/hess-2018-203
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
12 Jun 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Hydrology and Earth System Sciences (HESS).
Multiscale Roughness Influence on Conservative Solute Transport in Self-affine Fractures
Zhi Dou1,2, Brent Sleep2, Hongbin Zhan3, Zhifang Zhou1, and Jinguo Wang1 1School of Earth Sciences and Engineering, Hohai University, Nanjing, 210098 China
2Department of Civil Engineering, University of Toronto, 35 St. George Street, Toronto, ON M5S 1A4, Canada
3Department of Geology and Geophysics, Texas A&M University, College Station, TX 77843-3115, USA
Abstract. In this article, the influence of multiscale roughness on transport of a conservative solute through a self-affine fracture was investigated. The fracture roughness was decomposed into two different scales (i.e., a small-scale stationary secondary roughness superimposed on a large-scale non-stationary primary roughness) by a wavelet analysis technique. The fluid flow in the single fracture was characterized by Forchheimer's law and exhibited nonlinear flow features such as eddies and tortuous streamlines. The results indicated that the small-scale secondary roughness was primarily responsible for the nonlinear flow features. Numerical simulations of asymptotic conservative solute transport showed non-Fickian transport characteristics (i.e., early arrivals and long tails) in breakthrough curves (BTCs) and in residence time distributions (RTDs) with and without consideration of the secondary roughness. Analysis of multiscale BTCs and RTDs showed that the small-scale secondary roughness played a significant role in enhancing the non-Fickian transport characteristics. Removing small-scale secondary roughness delayed the arrival time and shortened the tail. The peak concentrations in BTCs decreased as the secondary roughness was removed, implying that the secondary roughness could also enhance the solute dilution. Fitting the one-dimensional (1D) Fickian advection-dispersion equation (ADE) to the numerical BTCs resulted in considerable errors that decreased with the small-scale secondary roughness being removed. The 1D mobile-immobile model (MIM) provided a better fit to the numerical BTCs and inclusion of the small-scale secondary roughness in numerical simulations resulted in a decreasing MIM mobile domain fraction and an increasing mass exchange rate between immobile and mobile domains.
Citation: Dou, Z., Sleep, B., Zhan, H., Zhou, Z., and Wang, J.: Multiscale Roughness Influence on Conservative Solute Transport in Self-affine Fractures, Hydrol. Earth Syst. Sci. Discuss., https://doi.org/10.5194/hess-2018-203, in review, 2018.
Zhi Dou et al.
Zhi Dou et al.
Zhi Dou et al.

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