超声在铝合金半连铸中搅拌作用的数值模拟

Numerical Simulation of the Stirring Action of Ultrasound in the Process of Semi-Continuous Casting Aluminum Alloy

针对含有相变的铸造过程,推导出了郎之万辐射压力梯度的矢量表达式,建立了声场、流场和温度场的耦合模型,并应用COMSOL Multiphysics软件求解出了声波频率为20kHz时的液穴内熔体流动速度分布和温度分布。模拟结果表明,超声处理能使熔体流动大幅度加强,形成流动漩涡,极大地增强了传热、传质和晶核的弥散;超声振动降低了过渡区域在圆坯轴向的温度梯度,使等轴晶更易形成。

For the process of casting accompanied by phase transformation, the vector expression of Langevin radiation pressure gradient was deduced, and the mathematical coupling model of ultrasound field, flow field and temperature field was established. Fluid velocity and temperature distribution were simulated by COMSOL Multiphysics software. The simulated results show that with ultrasonic vibration, melt flow is significantly enhanced, and large flow swirl occurs, which greatly enhance the heat and mass transfer as well as nucleation diffusion. Ultrasonic vibration considerably reduce the temperature gradient of the transition region in the axial direction of round billet, leading to easily forming equiaxed grains.