NUMERICAL SIMULATION OF OLDROYD-B VISCOELASTIC DROPLETS IMPACTING A CURVED WALL

The phenomenon of droplets impact on a curved wall widely exists in fields such as metallurgy, chemical engineering, and aerospace. In certain scenarios, droplets mixed with polymers may exhibit viscoelastic properties. Therefore, in order to further understand the influence of droplet viscoelasticity on the impact of curved walls, numerical simulation research was conducted on the process of viscoelastic droplets impacting curved walls. Based on the phase field method and lattice Boltzmann method (LBM), a three-phase viscoelastic flow field simulation method was developed to numerically simulate the impact of an Oldroyd-B viscoelastic droplet on a curved wall, in which the stress field distribution function solves the Oldroyd-B constitutive equation, and the contact Angle model of the curved wall is applied. The main focus is on the influence of viscosity ratio, Weber number, and wall contact angle on the impact process. The results indicated that the impact process consists of four main stages: the motion stage, the expansion stage, the stretching stage, and the tearing stage. As viscosity ratio β decreases, the kinetic energy decays faster in the expansion and stretching stage, the converted surface energy increases, and it enters the tearing stage earlier. After the droplet impacts the curved wall, it is easier to detach from the wall. The droplet mainly adheres or rebounds on the wall surface when the Weber number is small, and may tear and detach from the wall when the Weber number is large. As the Weber number increases, the kinetic energy of the droplet decays more rapidly during the expansion and stretching stage, and it enters the tearing stage more slowly. The hydrophilicity and hydrophobicity of the wall surface affect the final state of the droplet. The higher the hydrophobicity, the stronger the obstruction effect on the spreading stage, and the easier it is for the droplet to tear and detach.