Research On High Accuracy Multiphase Curved Boundary Algorithm Based On Lattice Boltzmann Method

The Multiphase flow phenomenon widely exists in nature,daily life and industrial and agricultural production,and it is essential to study it phenomenon deeply.With the development of high performance computing technology,numerical simulation has become an essential tool for studying multiphase flow.The lattice Boltzmann method is favored by people because of its clear concept and natural parallelism.It has developed into one of the main numerical simulation methods for studying multiphase flow,especially in dealing with complex boundaries with apparent advantages.In the lattice Boltzmann method,the curved boundary algorithm effectively improves the simulation accuracy of single-phase flow systems.However,in the multiphase environment,these algorithms cause the mass non-conservation of the system,leading to the multiphase flow simulation system’s collapse and limiting the multiphase flow simulation’s accuracy.In this paper,a multiphase flow curved boundary algorithm is successfully developed and applied to a variety of curved systems,and the work includes the following aspects:1.Analyze the problems of the interpolation boundary algorithm and propose a new high accuracy algorithm.When the interpolation boundary algorithm is applied to multiphase flow simulation,it is found that the interpolation boundary algorithm will cause the mass non-conservation of the system in multiphase flow simulation;mainly when the simulated solid is hydrophilic,the algorithm will cause the mass loss of the simulated system,and when the simulated solid is hydrophobic,the algorithm will cause the mass of the simulated system to increase.On this basis,the analysis finds that since the boundary algorithm can generate new distribution functions,it serves as a collision step of the lattice Boltzmann method,and therefore non-ideal effects should be considered in its process to reflect the surface wettability.Secondly,in the multiphase flow simulation system,the density distribution of the whole phase transition region is highly nonlinear,and the boundary algorithm can also produce considerable computational errors in the three-phase contact region in the simulation.Therefore,non-ideal effects and interpolation errors must be properly handled when applying the curved boundary algorithm in multiphase flow simulations.The high accuracy multiphase flow curved boundary algorithm developed in this study is obtained by correctly handling the non-ideal effects and interpolation errors.2.Analysis and compare the effectiveness of the new multiphase flow curved boundary algorithm.The validity of the new curved boundary algorithm is tested on the established multiphase flow models with flat and curved boundary,and compared with the simulation results of applying the linear interpolation boundary algorithm.The results show that the new curved boundary algorithm scheme is accurate and ensures the mass conservation of the simulated system;meanwhile,compared with other mass-conserving multiphase flow curved boundary algorithms,the new algorithm has a small artificially compensated mass and has a small spurious current during the simulation,which reflects the high efficiency of the new algorithm.3.The new curved boundary algorithm is applied to simulate the multiphase flow dynamics with curved boundaries.The high accuracy curved boundary algorithm of multiphase flow is applied to the simulation of the static droplet model,droplet impacting solid surface model and droplet hysteresis model on the heterogeneous surface,and all three applications show the effectiveness of the high accuracy curved boundary algorithm,especially the simulation data of droplet impacting surface solid is compared with the real experimental data,which shows the accuracy of the algorithm in simulation experiments.In this paper,a high accuracy curved boundary algorithm for multiphase flow is designed based on the lattice Boltzmann method,which is not only able to accurately portray the wetting boundary with complex geometry,but also ensure the mass conservation of the simulation system.The new algorithm can be applied to a series of static and dynamic simulations with large density ratios,providing some algorithmic references for the improvement of numerical simulation accuracy and realistic application of curved boundaries in multiphase flow.