Numerical simulation of a two layered water flow by means of the Lattice Boltzmann Method

In this paper the dynamics of a two-layered liquid, made of two immiscible shallow-layers of different density, has been investigated within the framework of the Lattice Boltzmann Method (hereinafter indicated as LBM). The LBM developed in this paper for the two-layered, shallow-water flow has been obtained considering two separate sets of LBM equations, one for each layer. The coupling terms between the two sets have been defined as external forces, acted on one layer by the other. Results obtained from the LBM developed in this paper are compared with numerical results obtained solving the two layered, shallow-water equations, with experimental and other numerical results published in literature. The results are interesting. Firstly, the numerical results obtained by the LBM and by the shallow-water model (hereinafter indicated as SWM) can be considered as equivalent. Secondly, the LBM developed in this paper is able to simulate motion conditions on not-flat topography. Thirdly, the agreement between the LBM (and also SWM) numerical results and the experimental results is good when the evolution of the flow does not depend on the viscosity, i.e. during the initial phase of the flow, dominated by gravity and inertia forces. When the viscous forces dominate the evolution of the flow the agreement between numerical and experimental results depends strongly on the viscosity: it is good if the numerical LBM viscosity has the same order of magnitude of the liquid’s kinematic viscosity