Solute dispersion in natural fractures is critical for groundwater contamination prediction. Fracture geometry-particularly pore-throat ratio(R (R=rmax/rmin)), surface roughness(Ra), and average pore radius("r"  ̅)-exerts significant but poorly understood coupled effects on dispersion. Using stochastically generated rough fracture models and COMSOL Multiphysics, this study simulates single fractures with varying R, Ra, and "r"  ̅, and quantifies the longitudinal dispersion coefficient ("D" _"l" ). Increasing R from 1 to 3.28 reduces "D" _"l"  by up to 60% with nonlinear decay. Higher Ra enhances the effect; at Ra = 0.08 mm, the "D" _"l"  decrease is nearly 20% greater than at Ra = 0.04 mm. A multivariate nonlinear regression model captures the synergistic parameter interactions and identifies the Ra·R coupling term as the dominant control. This work provides a theoretical foundation for contaminant transport assessment in fractured media.

Wanting Hu, Chenhao Li, Jiawen Cai. Study on the Solute Dispersion Mechanism under the Coupling Effect of Fracture Geometric Parameters. Academic Journal of Materials & Chemistry (2026), Vol. 7, Issue 1: 41-49. https://doi.org/10.25236/AJMC.2026.070107.

[1] Bodin J, Delay F, De Marsily G. Solute transport in a single fracture with negligible matrix permeability: 2. mathematical formalism[J]. Hydrogeology Journal, 2003, 11(4): 434-454.

[2] Cassell J S, Williams M M R. An integro-differential equation arising in radionuclide transport through fractured rock[J]. Mathematical Models and Methods in Applied Sciences, 1993, 3(5): 641-654.

[3] Jones T A, Detwiler R L. Mineral precipitation in fractures: using the level-set method to quantify the role of mineral heterogeneity on transport properties[J]. Water Resources Research, 2019, 55(5): 4186-4206.

[4] Zhao Z, Jing L, Neretnieks I, et al. Numerical modeling of stress effects on solute transport in fractured rocks[J]. Computers and Geotechnics, 2011, 38(2): 113-126.

[5] Boutt D F, Grasselli G, Fredrich J T, et al. Trapping zones: the effect of fracture roughness on the directional anisotropy of fluid flow and colloid transport in a single fracture[J]. Geophysical Research Letters, 2006, 33(21): 2006GL027275.

[6] Bodin J, Delay F, De Marsily G. Solute transport in a single fracture with negligible matrix permeability: 1. fundamental mechanisms[J]. Hydrogeology Journal, 2003, 11(4): 418-433.

[7] Hoagland D A, Prud’Homme R K. Taylor-Aris dispersion arising from flow in a sinusoidal tube[J]. AIChE Journal, 1985, 31(2): 236-244.

[8] Keller A A, Roberts P V, Kitanidis P K. Prediction of single phase transport parameters in a variable aperture fracture[J]. Geophysical Research Letters, 1995, 22(11): 1425-1428.

[9] Bouquain J, Méheust Y, Bolster D, et al. The impact of inertial effects on solute dispersion in a channel with periodically varying aperture[J]. Physics of Fluids, 2012, 24(8): 083602.

[10] Li B, Mo Y, Zou L, et al. Influence of surface roughness on fluid flow and solute transport through 3D crossed rock fractures[J]. Journal of Hydrology, 2020, 582: 124284.

[11] Zhang Q, Luo S, Ma H, et al. Simulation on the water flow affected by the shape and density of roughness elements in a single rough fracture[J]. Journal of Hydrology, 2019, 573: 456-468.

[12] Gelhar L W. Stochastic subsurface hydrology from theory to applications[J]. Water Resources Research, 1986, 22(9S): 135S-145S.

[13] Dronfield D G, Silliman S E. Velocity dependence of dispersion for transport through a single fracture of variable roughness[J]. Water Resources Research, 1993, 29(10): 3477-3483.

[14] Dejam M, Hassanzadeh H, Chen Z. Shear dispersion in a rough-walled fracture[J]. SPE Journal, 2018, 23(5): 1669-1688.

[15] Geetha Manjari K, Sivakumar Babu G L. Reliability and sensitivity analyses of discrete fracture network based contaminant transport model in fractured rocks[J]. Computers and Geotechnics, 2022, 145: 104674.

[16] Ozgumus T, Mobedi M. Effect of pore to throat size ratio on thermal dispersion in porous media[J]. International Journal of Thermal Sciences, 2016, 104: 135-145.

[17] Zhang S, Liu X, Wang E. Quantitative evaluation of the onset and evolution for the Non-Darcy behavior of the partially filled rough fracture[J]. Water Resources Research, 2024, 60(3): e2023WR036494.

[18] Chen Y F, Zhou J Q, Hu S H, Hu R, Zhou C B. Evaluation of Forchheimer equation coefficients for non-Darcy flow in deformable rough-walled fractures[J]. Journal of Hydrology, 2015, 529(3): 993-1006.

[19] Berkowitz B, Zhou J. Reactive solute transport in a single fracture[J]. Water Resources Research, 1996, 32(4): 901-913.