强迫对流影响枝晶生长的三维相场法模拟

Simulation of dendrite growth under influence of forced convection with three-dimensional phase-field method

将计算流体的三维模型与模拟枝晶生长的三维相场模型进行耦合,建立强迫对流环境下枝晶等温生长的三维PF-LBM模型,以Al-Cu合金为例研究液态金属流动时枝晶的生长行为、不同流速下枝晶的生长行为并在相同模拟参数条件下将三维模拟与二维模拟进行对比.结果表明:液态金属的流动显著改变了三维枝晶原有的对称生长形貌.不同流速下枝晶的生长形貌和溶质场分布不同,流动速度越大,迎流方向主枝晶越粗,逆流方向主枝晶越细.流动速度对尖端曲率半径的影响大于对尖端生长速度的影响,大的流动速度对逆流方向枝晶的影响比对迎流方向枝晶影响严重.三维模拟中液态金属的流动状况比二维模拟中复杂;相同模拟参数下三维模拟中液态金属的流动对枝晶生长的影响比二维模拟中影响大.

A three-dimensional PF-LBM model was established by coupling three-dimensional model for computational fluid and three-dimensional phase field model of dendritic crystal growth to simulate the isothermal growth of dendritic crystal in the condition of forced convection. Taking Al-Cu alloy as an example, the dendritic crystal growth behavior in liquid metal flow with different velocity was investigated. Under the condition of identical simulation parameters, the two-dimensional simulation was compared with the three-dimensional one. The results indicated that the original symmetric growth morphology of threedimensional dendritic crystal would be changed noticeably by the current of liquid metal. Dendritic crystal morphologies and solute field distributions were different under different flow velocities. When the flow velocity increased, the principal dendritic crystal would become thicker downstream and thinner upstream. The flow velocity of liquid metal had more effect on radius of curvature of tip than growing velocity of it and high flow velocity would have more effect on dendritic crystal upstream than downstream. The current of liquid metal in three-dimensional simulation was more complicated than that of two-dimensional simulation; the current of liquid metal would have more effect on dendritic crystal growth in three-dimensional simulation than that in two-dimensional simulation.