应用改进粒子水平集法对液滴碰撞的数值研究

为了准确捕捉自由面运动,求解液滴的碰撞过程,针对传统粒子水平集法不适用于待修正网格包含在虚拟粒子内部的情况,在充分分析以上问题的基础上提出一种新的局部距离函数定义方式.经测试问题验证,改进方法可降低由于粒子沿非界面法线方向运动对界面修正的干扰,显著提高界面捕捉精度及守恒性.应用改进粒子水平集法对二维液体碰撞过程进行数值模拟,计算结果显示:相对速度是正碰过程是否发生分离的决定因素,空气中两个直径为3mm的正碰水滴的临界韦伯数为13.79;偏心程度和相对速度共同影响偏心碰撞的液滴形态;给定相对速度时存在两个临界偏心程度,偏心程度介于临界值之间时碰撞后不发生分离.

Numerical Simulation on Droplets Collision with Improved Particle Level Set Method

The conventional particle level set method fails for the case when a mesh point to be corrected falls into an escaped particle.A novel local distance function correction approach was proposed in this study to capture the free surface movement and solve the process of droplet collision accurately.The verification by the deformation field problem confirms that the approach proposed can improve the accuracy of the interface capturing and the system mass conservation.The new approach was employed to simulate the process of 2D droplets collision.The results show that: for the normal collision,relative velocity is the key factor determining whether separation occurs after collision;the critical value of Weber number is 13.79 for two droplets with a diameter of 3 mm;the relative velocity and eccentricity both affect the separation pattern when an eccentric collision occurs;there are two critical eccentricities for a given relative velocity,and the separation will not occur when the eccentricity falls between the two critical eccentricities.