Droplet Viscoelastic Splash on a Soft Micropillared Surface

Liquid droplet impact on soft substrate decorated with micropillar array is simulated by finite volume method. Volume of fraction method is coupled with Navier-Stokes solver to rebuild the interfaces between two immiscible fluids. Standard linear solid (SLS) model for viscoelastic material is adopted in the modeling. Moreover, viscoelasticity is implemented on the substrate whose elasticity and viscosity are functions of the micropillar density, which are represented by the Maxwell series of the SLS model. As substrate deformation velocity is treated as Dirichlet boundary condition, the coupling between substrate motion and flow field is critical across different modeling domains. First order Euler time integration is used to obtain substrate deformation velocity. With diverse viscosity and elasticity applied, the deformation of various composite substrate is obtained. Furthermore, splashing threshold is explored by considering Weber number, ambient pressure and other factors. It turns out with Weber number and internal pressure raising, splashing magnitude are enhanced as impact time is shortened.