受迫流动下的枝晶生长相场法模拟研究

Denedritic growth in forced flow using the phase-field simulation

基于耦合流场和热噪声的相场模型及合理高效的三维动态求解域加速算法,定量模拟了在受迫流动下枝晶的非对称生长及流速对迎流、背流两侧的温度分布和层流层分布的影响.计算结果表明,受迫流动使迎流、背流两侧温度的分布与层流层分布呈现不对称状态,导致迎流侧与背流侧的过冷度不同,而熔体施加于枝晶界面前沿迎流侧的力还不足以抑制过冷度的作用,结果造成枝晶迎流方向优先生长,从而产生倾向于散热方向的倾斜;同时,由于迎流侧的实际过冷度大于背流侧,有利于促进迎流一侧枝晶生长速度以及稳定侧向分枝生长,从而导致了侧向分枝的非对称生长.随着流速的增加,枝晶倾斜程度越大,枝晶的不对称性越明显。

The assymmetrical dendritic growth and the effect of flow velocity on the temperature distribution and laminar flow boundary layer of both facing-flow side and against-flow side has been investigated numerically based on the phase-field model which incorporates both fluid flow and thermal noise,as well as reasonably high efficiency 3DAADCR.The computed results indicate that,the forced flow causes the dissymmetry of the distribution of the temperature distribution and laminar flow boundary layer of both facing-flow side and against-flow side,leading to the different undercooling on either sides,as a result,the dendritic growth towards the flow and inclination relative to the dissipating heat direction appear.At the same time,the undercooling of facing-flow side is greater than that of against-flow side,which is helpful to accelerate dendritic growth rate and makes the sidebranching steady growth,accordingly,resulting in assymmetrical sidebranching growth.With the increase of flow velocity,the greater the inclination,and the more obvious the assymmetrical degree.