Investigations On Gas-liquid-solid Three-phase Flow In Casting Filling Process Based On SPH Method

Mold filling flow is an important stage in the casting process,and it is necessary to obtain the high quality castings with a smooth filling process,reasonable filling sequence and filling time.Many defects,such as slag inclusion,air entrainment,misrun and cold shut,affect the casting quality in casting filling process.In the actual filling process,the mold cavity in the closed state,the liquid metal movement in the cavity is observed difficultly,and the use of simulation to predict the filling process of casting,is an important means to ensure the casting quality of production,shorten the trial period and reduce production cost.Although the traditional numerical simulation method based on grid method has been developed,it is difficult to deal with the free surface,the deformation boundary and the moving interface and the multiphase flow.The smoothed particle hydrodynamics(SPH)is a kind of Lagrangian particle method,can capture the free surface and multi phase interface movement by tracking the position of the particles,therefore investigation on free surface,moving substance interface and multiphase flow aspects have a great influence and application prospects.At present,the numerical simulation of mold filling process based on SPH method is still in the basic research stage,and there are still many key problems to be solved.In this paper,the following aspects are studied.In this paper,the concept and basic principle of SPH method are expounded,and the discrete control equations of casting filling process based on SPH are summarized.The basic properties of smooth functions are studied,and the accuracy and efficiency of several common smoothing functions are compared.Finally,the five smoothing function is defined as the kernel function of SPH filling process.Several common particle search methods are studied,and combined with the characteristics of mold filling process,it is found that the method of list search is used to solve the numerical simulation of SPH filling process.The SPH mold filling calculation program is established by Visual C++,and the correctness and validity of the SPH casting filling process are verified by the filling simulation of the two-dimensional plate.By introducing the surface tension model and dispersing the control equation of gas-liquid two-phase flow in SPH filling process and establishing the calculation model of SPH filling gas-liquid two-phase flow.The floating process of a single bubble is calculated,and the experimental results are basically consistent with the simulation results,which verifies that the established gas-liquid two-phase flow model is suitable for dealing with the problem of large density difference.The simulation results of the filling process of the bottom side injection chamber are consistent with the experimental results,which lays the foundation for the quantitative prediction of the casting defects such as porosity and gas volume.The influence of slag on the filling process of casting was studied,and the rigid body motion model was introduced,and the calculation program of solid-liquid two-phase flow in SPH mold filling process was established in this paper.The position of slag particles by computing on the filling process of plate-casting is consistent with the experimental results,it is proved that SPH method is correct and effective procedure of casting filling process of solid-liquid two-phase flow.The discrete control equations of gas-liquid-solid three-phase flow in SPH casting filling process are studied,and the model calculation program is established.By computing the three-phase of plate-casting flow filling process,and the results were compared with Win-Cast single phase flow,liquid metal flow trend is basically consistent,further validation of calculation program of the SPH casting process of gas-liquid-solid three-phase flow is correct and effective.