Dynamic behavior of metal droplet impact on dry smooth wall: SPH simulation and splash criteria

Abstract

Droplet impingement is a widespread phenomenon in nature and industrial production. Different from the problem of light drop/wall impact, which has been investigated early and sufficiently, few researches are found on the dynamic behavior and modeling of heavy drop impingement, which is widely existed in the field of plasma spray, 3D printing and ejecta mixing caused by detonation, etc. In this paper, the behavior of different metal drops impinging on dry smooth wall is studied based on Smoothed Particle Hydrodynamics (SPH) method. A newly splash threshold is proposed for heavy drop impact, and the difference of splash criteria between light drop and heavy drop is analyzed. The results show that incident kinetic energy is an important factor to determine the outcomes of heavy droplet impact. When the incident kinetic energy is relatively low, the metal droplet would spread, and the maximum spreading radius increases with the increase of kinetic energy. With higher incident kinetic energy, the droplet would splash, and the proportion of secondary droplets increases with the increase of incident kinetic energy. Higher droplet viscosity will hinder its spreading, but when splash occurs, it will promote the increase of secondary droplet. The increase of surface tension would suppress droplet spreading rate, but it has little effect on the maximum spreading radius. The splash criteria of heavy droplet impinging on dry smooth wall is proposed as K=Oh⋅Re1.5346=3341.95. The splash threshold of heavy droplet is higher than that of light droplet within the range of Re < 4000, owing to the higher surface tension of heavy droplet. When Re > 4000, the outcomes of light droplet impact show strong randomness, thus no uniform splash threshold can be found, while the metal droplet has a uniform splash threshold within the range of Re <100000.