The Numerical Simulation Study Of Macro Filed Coupling Microsteucture Of Ignots Solidification Process Based On CA-LBM Model

Preventing and controlling the sturtured defects are still the tough problems in the process of solidification.In order to solve these problems,it is necessary to understand the formation of macro-structure and the phenomenon of transport.The problem has been one of the widespread interesting and researchful point.With the development of computer,the simulation is becoming an important method in researching solidification.The simulated method have the important significance to learn about the formation of macro-structure,analyze the process of transfer,control and improve the defects.In this thesis,a two-dimensional cellular automaton(CA)-lattice Boltzmann(LB)coupling model is developd based on CA method of simulating the dendritic growth and LBM of calculating the transport.And the model adopt to a new method to simulate the soult transport.First,simulating the Poiseuille flow,the cavity natural convection,the diffusion of heat and solute by the LBM.Then,researching the dendritic growth by the coupling CALBM modelling.Last,analyzing the macro-structure of global ingot under different condicition.According to the above researchs,the resoults show as follows:(1)Simulated the Poiseuille flow,the cavity natural convection,the diffusion of heat and solute,compared the simulated results with relative analytical solutions.The results show reasonability and reliability of LB modeling.(2)Simulated the dendritic growth with natural convection and without convection,compared the analytical solutions.The results show that the coupling model can really simulate the dendritic growth.(3)Simulated the effect of coefficient,cooling date,convection on dendritic growth.The results indicate: the primary dendrite arms becomes thinner with increasing anisotropy.The finger channel becomes wider with increasing Gibbs-Thomson.Low enough anisotropy and Gibbs-Thomson result in the growth of instabilities,which lead to the high branching of the dendrites.Convection producing asymmetrical dendrites,and the phenomenon of asymmetrical intensify with increasing convection.(4)Simulated and analyzed the tranafer of CET with different condition,which show:the convection influence the structure of CET and transport of heat and solute.There are indistinct sturcture of CET,thick dendrites,fast solidification when the pouring temperature is low.And when heat transfer coefficient is enough in a limited condition,there are thick dendrites and long columnar dendrites.The columnar dendrites are not obvious and the solidifiction is fast,when the ingnot is smaller.(5)Compared the results of experiment with simulation,which indicate: the dendritic morphologies with forced convection and CET of simulations are agreed with the experiment.Improtantly,it released that the modelling of CA-LBM is reliable and effective to simulate solidification,including the processess of microstructure and tranfer.