A lattice Boltzmann method with two relaxation times for shallow-water equations (LABSWETRT) without turbulence is proposed. The described model is validated through simulations of three typical cases with laminar flows: 1D steady flow over a bump, 2D unsteady dam-break flow, and flow around circular cylinder. Good agreement between prediction and analytical or experimental solutions are obtained. In addition, the performance of the LABSWETRT and the lattice Boltzmann method for shallow-water equations using a single relaxation time (LABSWE) is compared in detail. Studies have shown that the former is more stable than the latter for 2D cases. Different combinations of the two relaxation times are also studied and the optimized one is recommended for good numerical stability. This study demonstrates that the additional relaxation time in the LABSWETRT can improve the stability of simulations for laminar shallow flows using a procedure almost as simple as that in the LABSWE.

In this paper, an improved lattice Boltzmann Shan‒Chen model coupled with Carnahan-Starling equation of state (C-S EOS) and the exact differential method (EDM) force scheme is used to simulate the cavitation bubble collapse in the near-wall region. First, the collapse of a single cavitation bubble in the near-wall region was simulated; the results were in good agreement with the physical experiment and the stability of the model was verified. Then the simulated model was used to simulate the collapse of two cavitation bubbles in the near-wall region. The main connection between the two cavitation bubble centre lines and the wall surface had a 45° angle and parallel and the evolution law of cavitation bubbles in the near-wall region is obtained. Finally, the effects of a single cavitation bubble and double cavitation bubble on the wall surface in the near-wall region are compared, which can be used to study the method to reduce the influence of cavitation on solid materials in practical engineering. The cavitation bubble collapse process under a two-dimensional pressure field is visualized, and the flow field is used to describe the morphological changes of cavitation bubble collapse in the near-wall region. The improved lattice Boltzmann Method (LBM) Shan‒Chen model has many advantages in simulating cavitation problems, and will provide a reference for further simulations.