单液滴冲击多孔介质过程的数值模拟与试验

Process Simulation and Experiments of Single Droplet Impactingon Porous Materials

三维打印过程中,粘结剂的性能及动态行为对打印过程的质量有重要影响。本文中分析了单液滴对多孔介质的冲击、扩展、渗透动态过程,建立了液滴动态变化的数学模型。为了准确描述液滴流动的动态效果,采用VOF(Volume of fluid)模型来跟踪液滴形状,采用PISO(Pressure implicit split operator)算法计算压力速度耦合。分析了液滴特性、冲击速度和多孔介质孔隙率对液滴扩展特性的影响。试验结果表明,提出的模型可以进行良好的预测,同时发现液滴最大扩展半径随液滴初始速度的增加而增加,随粘度的增加而减小;孔隙率越小,液滴在多孔介质外部的扩展明显,扩展半径变大,渗透厚度变小。

In three-dimensional printing process, the behavior and the properties of the droplet has an great impact on the quality of the printed parts when the binder penetrate into the materials. This paper established a numerical model to study the impact process of a single droplet on the porous media, including the expansion, penetration. In order to accurately describe the dynamic effect of the droplet flow, VOF （Volume of fluid） model is used to track the droplet shape. The PISO （Pressure implicit split operator） algorithm is selected to solve the pressure-velocity combinations. the effect of the droplet characteristics, the impact velocity of the droplet and porosity of the porous media on droplet expansion characteristics was focused. The results showed that the droplet extension radius increases with the increasing of initial droplet velocity and decrease with the increasing of viscosity; the smaller the porosity of the porous media is and the bigger the expansion radius of the droplet, the smaller the penetration thickness.