Multi-field Coupled Phase Field Model Of PF-LBM Based On OpenCL Parallel

The phase field method(PF)based on Ginzburg-Landau theory,it is one of the most potential effective calculation techniques in the simulation of solidification structure.It does not need to track the solid-liquid interface,and it is convenient to introduce external fields such as flow into the phase field governing equation.Lattice Boltzmann Method(LBM)is not only satisfied with the calculation of multiphase flow,but also can deal with arbitrarily complex boundaries.It has high computational efficiency,good numerical stability,inherent parallelism,it is easy to deal with arbitrarily complex boundary problems and many other traditional methods do not have this unique advantage.In this paper,based on the phase field model and the lattice Boltzmann method(LBM)for calculating momentum,mass and energy transfer,the PF-LBM model is established by coupling temperature field,solute field,flow field and other external fields,taking pure matter and Al-4.5wt%Cu alloy as an example,Carry out the numerical simulation under the coupled condition of multi-physics process to study the influence of flow on the growth of two-dimensional pure substance dendrite and the solidification growth of Al-4.5wt%Cu binary alloy,as well as the influence of solidification growth on flow.In view of the multi-scale and traditional finite-difference method based on uniform grid in the simulation calculation of multi-field coupled phase-field model,the problem of large calculation amount,low computational efficiency,and limited qualitative research in solving the phase field model on a single CPU is studied.The GPU-based high-performance computing method realizes the parallelization of the algorithm for solving the phase field model in the two-dimensional area,so as to expand the simulation scale,improve the accuracy of the solution and the efficiency of the calculation.On the CPU+GPU heterogeneous multi-node cluster platform,the Open CL parallel computing method is used to solve the numerical simulation of the multi-field coupled PF-LBM phase field model.In order to verify the reliability and validity of the Open CL parallel calculation method in the numerical calculation of dendrite growth under simulated flow,the results of the Open CL parallel calculation method to solve the PF-LBM phase field model were compared with the CPU serial results.Under the same conditions,Compared with the CPU-based simulationcalculation time,the Open CL parallel calculation method has a significant reduction in the solution time and a significant increase in calculation efficiency.On a simulation area of ??1200×1200 grid,the Open CL parallel calculation method on a single GPU achieves a 7.6 times speedup.The dendrite growth in forced convection and natural convection was simulated.The simulation results show that under forced convection,single dendrites grow asymmetrically under the influence of the flow field during the growth process.The higher the flow velocity,the more obvious asymmetric growth.During the growth of multiple dendrites,as the dendrite spacing decreases and the solute concentration increases,the dendrites grow asymmetrically,the flow effect gradually weakens,the dendrite arms appear to oppose each other and grow,and the dendrites show irregular shapes.Under the action of natural convection,as the single dendrite grows,the interface temperature rises,and the flow field is gradually divided into four small eddy regions.The flow effect changes the dendrite growth behavior,promotes the growth of the dendrites in the upstream direction,and the increase in temperature gradient increases the strength of the natural convection flow field.