Numerical Simulation On Submerged Plane Water Jets Based On Free Energy Lattice Boltzmann Method

A submerged, vertical plane jet impinging onto a free water surface will be self-excited into a flapping motion when the jet exit velocity exceeds a critical value. As we know, the self-excited flapping motion is due to the jet instability; however, the mechanism of this motion is still ambiguous.In this paper, based on theoretical analysis of flapping motion with experimental data, it is verified that the value of flapping factor k tf and the value of Reynolds factor k tare with the same order. Those results imply the fact that the effect of the flapping-induced shear stresses on the flapping motion can not be neglected.The lattice Boltzmann method is a novel mesoscale approach of numerical simulation for fluid hydrodynamics from the discrete movement theory and statistic physics, and has been applied to fluid flow and heat transfer simulations. Free energy LBM is used as a development of the basic model of standard LBM to simulate multiphase and multi-component fluid. It is a method of diffuse interface to capture the moving interface of binary fluids. In this paper, the free energy LBM is applied to investigate the properties of the submerged plane water jets under different conditions. The results show that:(1) The method is suitable to simulate the plane water jets with large density ratio and free surface, and will be used to simulate the flapping motion as a novel way.(2) The mean velocity decay rules along the jet centerline are consistent with the theory of impinging jet.(3) The change of the mean velocity decay exponent along the jet centerline and the existence of the additive exponent decay factor will imply the trend of the flapping motion.