Lattice Boltzmann Method Applied In Flood Routing

Lattice Boltzmann (LB) method was developed into a flow-field simulating scheme in the middle of 1980s. Compared with traditional numerical methods, the LB method has several important features, including: simplicity in algorithm, easily programming, direct calculation of pressure from a state equation and amenability to simulate all kinds of flow field with complex boundaries, it also has many advantages in the respect of parallel computation because of its regional evolution. Although, there has a progress in employing the lattice Boltzmann equation for fluid dynamics and modeling complex physics in fluids recently, there are some problems to be solved, such as the negativity of discrete local equilibrium or evolutionary distribution and the limitation of low Mach number. The application of the lattice Boltzmann method in unsteady open channel flows was studied in detail in the paper. An existing lattice BGK model was mended; For the problem of negative local equilibrium and evolutionary distribution, we proposed a lattice Boltzmann model based on cell-population equilibrium, which is a direct non-negative approximation to the continuous Maxwell distribution. The model reduces the transport and collision, two basic evolution steps in the LB model, to transport of the non-equilibrium distribution. Furthermore, this model permits the particles changes in much more lattices instead of neighbour lattices only. This scheme increases the numerical stability of the LBM in simulating open channel fluid flow. In the LBM, the discrete speed is often taken finite values, and is limit to simulate low Mach number flow. The finite volume KFVS method, based on the Boltzmann equation, breaks through the low Mach number and can simulate rush flow. We established a new method by combining the particle speed distribution on the boundary of dry and wet ground and applied it in moving boundary problem. Numerical test showed that this model was reliable. In this paper, 1-D dambreak and 2-D dambreak with dry bed were simulated by the models mentioned above respectively, and the numerical result showed that the models were feasible and efficient.