Impact force and spreading characteristics of droplet impact on cylindrical surfaces

TL;DR

This study uses numerical simulations to analyze droplet impact on cylindrical surfaces, revealing force dynamics, spreading behavior, and effects of wettability and geometry, which were less explored compared to flat surfaces.

Contribution

It provides new insights into impact force characteristics and spreading behavior of droplets on cylindrical surfaces, including force peak relationships and effects of surface wettability and geometry.

Findings

Impact force exhibits single or double peaks depending on impact mode.

Impact force peak approaches a constant with increasing Weber number.

Spreading and asymmetry follow power-law relationships with Weber and Ohnesorge numbers.

Abstract

Droplet impact phenomena are ubiquitous in both nature and industry. Existing studies of droplet impact have focused on the kinematics of droplet impact on flat surfaces, whereas research on cylindrical surfaces remains relatively limited, particularly from a force-based perspective. Here, droplet impact on cylindrical surfaces is studied by numerical simulation, with particular attention to the spreading behavior and impact force acting on the wall. In the deposition mode, a single peak appears in the impact force curve, which corresponds to the rapid transfer of the droplet's initial momentum. In the rebound mode, two distinct peaks are observed, and the second peak arises from the reaction force during the retraction process. Increasing the surface wettability causes the asymmetry coefficient, the ratio of the maximum spreading lengths in the azimuthal and axial directions of the cylinder, to first decrease and then gradually approach a constant, while the effect of the surface wettability on the initial impact force is negligible. As the Weber number We increases, the first dimensionless peak of the impact force $F_{p1}^{*}$ approaches a constant, and the relationship can be expressed as $F_{p1}^{*}={\beta}_1+{{\beta}_2}{{We}^{-1}}$ (where ${\beta }_1$ and ${\beta }_2$ are constants). The dimensionless maximum spreading area, dimensionless maximum spreading length, dimensionless maximum spreading angle, and asymmetry coefficient all exhibit power-law relationships with the Weber and Ohnesorge numbers. Furthermore, an increase in the diameter ratio of the cylinder and the droplet leads to a reduction in the asymmetry coefficient and an increase in the first dimensionless peak of the impact force.