Numerical analysis of hollow droplet impacts on a dry flat surface

Abstract

Hollow droplet impacting on a dry fat surface has obvious difference in its dynamics and heat transfer behaviors comparing with continuous dense droplet impact. In the present research, a numerical model based on coupled level set and volume of fraction (CLSVOF) method is applied to investigate dynamics and heat transfer of a hollow droplet impact on a dry flat surface. Dynamics and heat transfer of hollow droplet with high and atmospheric cavitation-bubble pressure are compared with that of continues dense droplet. Both atmospheric-cavitation-pressure (ACP) and high-cavitation-pressure (HCP) hollow droplet appear obvious spreading and central counter-jet features after impact. However, the central counter jet is not observed in a continuous dense droplet impact. Pressure difference inside hollow droplet is the main reason leading to droplet spreading and central counter jet formation. HCP hollow droplet expands before impact and the diameter increasing is found to be closely related to Re. HCP hollow droplet has a smaller spread factor and average wall heat flux, while a larger dimensionless height of counter jet than those of ACP hollow droplet. Moreover, compared with continuous dense droplet, hollow droplet has a smaller spread factor and average wall heat flux.