Numerical Simulation Study On Lattice Boltzmann Method For Seturated Soil Seepage

The Lattice Boltzmann Method (LBM) developed in 1980s has gradually infiltrated from the initial CFD applications to other fields and has became one of the international research focuses. LBM based on the microscopic discrete model and some micro-dynamic equations, and the simulation system is established using discrete speed sets in the way of Down-top, which has the characteristics of Euler method and Langrange method. With the traditional CFD methods, LBM has some advantages, such as simple algorithm, easy programming, easy to handle complex boundary conditions, adapt naturally to large-scale parallel computing and so on, which makes it very appropriate to study the seepage problems.In this paper, LBM as the breakthrough point, after understanding the key of using LBM to solve seepage problems lies in establishing suitable for the evolution equation of seepage movement, the evolution equations and local equilibrium distribution function of conventional LBM for the amendment, that is, the constraint force, porous media imposed to fluid, is added in the right side of the evolution equation of conventional LBM(the constraint force can be written in power series of discrete speed sets), and porosity is introduced in the local equilibrium distribution function; and then the specific expression and reasonable discrete form of the force are determined. This has laid a theoretical foundation for using LBM solve to seepage problems.Furthermore, in the basis of digestion and absorption the related results of theory and applications of LBM in recent years, the software platform(LBM_Seepage) for simulating saturated soil seepage with LBM theory is initially developed. The Pre-processing module of the software not only has a more comprehensive mapping functionality, but also provide interface for interacting with other graphical documents, using it can easily complete the drawing of flow field geometry section; the LBGK model and the non-equilibrium extrapolation format are used in the core of the core module of the software, which not only speed up the convergence rate, but also enable the evolution equation to approximate to second-order accuracy in time and space; a wide range of data visualization software package is used in the Post-processing module of the software, which greatly expanded the functions of LBM_Seepage.In order to verify the correctness of LBM_Seepage, first, Darcy's law is verified with the software, and then in the REV scale the software is used to simulate the groundwater movements under many cases and the vertical seepage of layered soil samples, and the verification and comparison with the indoor experimental results are performed. In addition, in the pore scale, water flow rule in the artificial rough fracture and seepage characteristic of variable porosity porous media are simulated with the software, and the verification and comparison are performed also. Study shows that the software platform has a certain degree of flexibility, effectiveness and extendibility, and it is expected to become a powerful tool for research seepage movement.