Numerical Simulation Study Of Flow In Single Rough Fractures Based On Fluent

Groundwater resource is an important part of water resources in China. Especially in the north area, fracture groundwater served as the significant water source of agriculture and civil living. However, due to the activities like inappropriate utilization, garbage landfill and deep reserving of radioactive wastes, a series of negative effect emerged in the aspect of water recourse, water environment and geology environment. Therefore, researches on modeling and simulation of groundwater environment play an important role for the conservation and sustainable utilization of groundwater. In China, The state of researches on the fracture flow movement goes at the stage of theoretic and experimental exploration. The study need to be deepened, and the methods should varied. Supported by the project"Research on the experiment and simulation of solute Non-Fickian transport in rock fractures"(40872166) of the National Natural Science Foundation of China, the thesis discuses flow mechanism in different rough fracture models.One of the most important methods of researching fluid fields in fractures is flow simulation with mathematics models for their high efficiency, flexibility and relative cheapness. Based on the review of studies on numerical simulation on groundwater flow, the author established three 2D fracture models with different rough forms (rectangle, triangle and sinusoid), and compared the accuracy of four different flow models.Subsequently, the distribution of fluid fields in different fractures are simulated by the optimized flow model and analyzed. Results can be concluded as below:1) All the models of Laminar, standard k-ε, RNG k-εand Spalart-Allmaras can be used to simulate the fluid fields in rough fractures. But the standard k-εmodel is the best for its calculation accuracy and quick convergence speed.2) In rough fractures, traditional Darcy theorem can not characterize the flow, the velocity of flow v and hydraulic gradient J have exponential relations rather than linear. Besides, The Local Cubic Law (LCL) does not fit these fluid fields.3) In rough fractures with different structure, rough configuration's effects on fluid flow vary. A smooth rough configuration has the smaller influence on flow than a coarse one. In the cases of the paper, the turbulent effect from fracture with sinusoid configuration is the smallest, that form triangle fracture is moderate, and that from the rectangle ones have the strongest effect.4) In single rough fracture the turbulence strength increases with the growing of relative roughness. In amendatory LCL, the value of m relates to the relative roughness; the value of m gets close to 1 as the relative roughness becomes smaller, that is the wall is getting smooth. Another factor that effects m is the rough configuration, the value of m decrease with its undulation intensively.5) In amendatory LCL, the value of n increases with the growth of flow velocity. It is larger than 3 in non-mating rough fractures, which means the relation between discharge of seepage and average aperture accord with super-cubic law. The n value is smaller than 3 in mating rough fractures, which means the relation between discharge of seepage and average aperture accord with sub-cubic law. The rough configuration has influence on the value of n, comparing fractures with rectangle, triangle and sinusoid configurations, the value of n in sinusoid fractures is closer to 3 than the other two. The reason lies in the light effect on fluid flow by a change of its wall is smooth.6) In rough fractures, the recirculation will occur where the aperture change suddenly for the roughness of wall. Recirculation areas depend on the figure of rough structure and velocity of flow. At the same flow velocity, with rough walls fluctuate intensively, the recirculation is strong, also the recirculation areas enlarge.