三维PTT黏弹性液滴撞击固壁面问题的改进SPH模拟

Numerical Simulation of 3D PTT Droplet Impact Onto Solid Surface With an Improved Smoothed Particle Hydrodynamics Method

基于光滑粒子动力学(smoothed particle hydrodynamics,SPH)方法,对三维Phan-ThienTanner(PTT)黏弹性液滴撞击固壁面问题进行了数值模拟.为了有效地防止粒子穿透固壁,且缩减三维数值模拟所消耗的计算时间,提出了一种适合三维数值模拟的改进固壁边界处理方法.为了消除张力不稳定性问题,采用一种简化的人工应力技术.应用改进SPH方法对三维PTT黏弹性液滴撞击固壁面问题进行了数值模拟,精细地捕捉了液滴在不同时刻的自由面,讨论了PTT黏弹性液滴不同于Newton(牛顿)液滴的流动特征,分析了PTT拉伸参数对液滴宽度、高度和弹性收缩比等的影响.模拟结果表明,改进SPH方法能够有效而准确地描述三维PTT黏弹性液滴撞击固壁面问题的复杂流变特性和自由面变化特征.

Based on an improved smoothed particle hydrodynamics （SPH） method, the spreading deformation of 3D PTT droplets impacting onto solid surface was numerically simulated. In order to prevent the fluid particles from crossing the suface, an improved treatment technique for the surface boundary was proposed, which can drastically reduce the consumed CPU time for 3D numerical simulation. Furthermore, an artificial stress term was added to the momentum equation to remove the so-called tensile instability. The dynamic processes of 3D PTT droplets impacting onto solid surface were numerically simulated with the improved SPH method. The different flowing features between the Newtonian and PTT fluid droplets during impacting were discussed. The effects of the elongational parameter on the collision behavior were analyzed in detail. The simulation results demonstrate that the improved SPH method can effectively describe the rheological characteristics of 3D PTT droplets impacting onto solid surface.