运用一种改进光滑粒子动力学(SPH)方法模拟了相溶和不相溶两种情况下的等直径微液滴碰撞动力学过程.为提高传统SPH方法的数值精度和稳定性,采用一种不涉及核导数计算的核梯度改进形式;为处理液滴界面张力采用修正的van der Waals表面张...运用一种改进光滑粒子动力学(SPH)方法模拟了相溶和不相溶两种情况下的等直径微液滴碰撞动力学过程.为提高传统SPH方法的数值精度和稳定性,采用一种不涉及核导数计算的核梯度改进形式;为处理液滴界面张力采用修正的van der Waals表面张力模型.通过模拟牛顿液滴碰撞聚并变形过程并与相关文献或试验结果进行对比,验证了改进SPH方法模拟微液滴碰撞过程的可靠性.随后,研究了基于van der Waals模型相溶聚合物微液滴碰撞聚并变形过程及不相溶微液滴碰撞后的反弹、分离过程,讨论了碰撞过程中碰撞速度、碰撞角度、密度比等参数对碰撞变形过程的影响,分析了流体桥、旋转角度等因素的变化情况.展开更多
The trajectory model of dispersed phase drops and the model of basic flow for drop motion between two inclined parallel plates are derived with the optimized calculation. The analytical results of direct numerical sim...The trajectory model of dispersed phase drops and the model of basic flow for drop motion between two inclined parallel plates are derived with the optimized calculation. The analytical results of direct numerical simulation indicate that the basic flow plays an important role in the drop coalescence on liquid-liquid interface. In the stratified two-phase flow field, the smaller droplets are difficult to drain the thin continuous film between the approaching droplets and bulk interfaces and eventually immerse into the trickling film to yield coalescence. They almost attain the velocity of their local surroundings. Moreover, the basic flow exerts a dominant influence on the motion of smaller droplet. The smaller droplets are easily entrained by the basic flow. On the contrary, the larger drop presents advantageous characteristics of coalescence due to its high velocity. The range of 0.3 mm < δR≤ 0.75 mm is the advantageous drop coalescence condition since the rapidly varied velocity and its first derivative theoretically cause the forces acting on a drop to become imbalanced. On the other hand, the thin layer of the continuous phase drained from the interval between the drops and trickling film should not be neglected in the calculation of shearing force since it is important for drop rotation. The drop rotation is an indispensable factor in coalescence.展开更多
文摘运用一种改进光滑粒子动力学(SPH)方法模拟了相溶和不相溶两种情况下的等直径微液滴碰撞动力学过程.为提高传统SPH方法的数值精度和稳定性,采用一种不涉及核导数计算的核梯度改进形式;为处理液滴界面张力采用修正的van der Waals表面张力模型.通过模拟牛顿液滴碰撞聚并变形过程并与相关文献或试验结果进行对比,验证了改进SPH方法模拟微液滴碰撞过程的可靠性.随后,研究了基于van der Waals模型相溶聚合物微液滴碰撞聚并变形过程及不相溶微液滴碰撞后的反弹、分离过程,讨论了碰撞过程中碰撞速度、碰撞角度、密度比等参数对碰撞变形过程的影响,分析了流体桥、旋转角度等因素的变化情况.
基金Supported by Natural Science Foundation of Tianjin (No. 09JCYBJC06400)Science and Technology Foundation of Civil Aviation Administration of China (No. MHRDZ200802)
文摘The trajectory model of dispersed phase drops and the model of basic flow for drop motion between two inclined parallel plates are derived with the optimized calculation. The analytical results of direct numerical simulation indicate that the basic flow plays an important role in the drop coalescence on liquid-liquid interface. In the stratified two-phase flow field, the smaller droplets are difficult to drain the thin continuous film between the approaching droplets and bulk interfaces and eventually immerse into the trickling film to yield coalescence. They almost attain the velocity of their local surroundings. Moreover, the basic flow exerts a dominant influence on the motion of smaller droplet. The smaller droplets are easily entrained by the basic flow. On the contrary, the larger drop presents advantageous characteristics of coalescence due to its high velocity. The range of 0.3 mm < δR≤ 0.75 mm is the advantageous drop coalescence condition since the rapidly varied velocity and its first derivative theoretically cause the forces acting on a drop to become imbalanced. On the other hand, the thin layer of the continuous phase drained from the interval between the drops and trickling film should not be neglected in the calculation of shearing force since it is important for drop rotation. The drop rotation is an indispensable factor in coalescence.
