Flow State of Single Rough Fracture Based on Lattice Boltzmann Method

Based on the lattice Boltzmann method and D2G9 discrete model, a single fracture seepage model was established considering different roughness, with the advantages of the easy setting of boundary conditions, high computational efficiency, and visualization of calculation results. The upper and lower boundaries of the model were set as full rebound boundaries without slip. The distribution function boundary of the left and right edges was used in the non-equilibrium extrapolation format, and the model is verified with the Poiseuille flow problem of classical fluid mechanics. Finally, the influence of the surface roughness of rock fracture on the seepage state was analyzed. The calculation results showed that with the increase of the roughness of the wall surface, the flow velocity, size, and direction of the fluid will change to different degrees. In the parts where the gap width changes sharply due to the change of roughness, the formation of local fluid vortices will lead to the increase of internal friction resistance of the fluid, resulting in greater local energy loss.