液滴撞击液膜的射流与水花形成机理分析

建立了单液滴撞击平面液膜的物理与数学模型,采用Coupled Level Set and Volume of Fluid方法对这种现象进行了数值模拟,探讨了黏度和表面张力对冠状水花形态的影响.通过分析撞击后液体内部的压力和速度分布,揭示了液滴颈部射流的产生机理,验证了Yarin和Weiss提出的运动间断理论.研究显示,表面张力对冠状水花形态的影响远大于黏度的影响.颈部射流的产生主要是由于撞击后颈部区域局部较大压差造成的,随着撞击过程的继续,压差作用减弱;液膜内流体的径向运动对射流发展成冠状水花具有推动作用.

Analysis of liquid sheet and jet flow mechanism after droplet impinging onto liquid film

Physical and mathematical models are established to simulate the phenomenon of single droplet impinging onto flat liquid film by using the coupled level set and volume of fluid method, and influences of viscosity and surface tension on the morphology of the crown liquid sheet are discussed. Besides, the mechanism of jet flow in the neck region is revealed and the theory of kinematic discontinuity proposed by Yarin and Weiss is verified by analyzing the distributions of pressure and velocity after impingement. The research result shows that the effect of surface tension on the crown morphology is far stronger than that of viscosity. Generation of jet flow is due to the higher pressure difference, the effect of which becomes weak with impact evolution and the jet flow is developed into the crown gradually with the help of radial flow in the liquid film.