An Experimental Study on the Effect of Surface Roughness on the Impact of Newtonian Droplets on Spherical Surfaces

Authors

1 Mechanical Engineering, Shahrood University of Technology

2 Mechanical Engineering, Shahrood University of Technology, Shahrood, Iran

10.22044/jsfm.2026.16536.3997

Abstract

In this study, the dynamic behavior of Newtonian droplets composed of various glycerin–water mixtures impacting spherical surfaces with different roughness and curvature was experimentally investigated. The effects of fluid viscosity, impact velocity, surface roughness, local curvature, and the sphere-to-drop diameter ratio (D*) on spreading, recoiling, and splashing were evaluated. Results showed that lower viscosity fluids exhibited higher maximum spreading factor (βmax) and dynamic recoiling, whereas higher viscosity fluids experienced greater energy dissipation, resulting in limited spreading and weaker recoiling. Increasing impact velocity led to higher βmax and delayed time to maximum spread. Higher surface roughness induced secondary splashing and instability during spreading, while greater curvature facilitated spreading. The interplay between roughness and curvature revealed that curvature played a more dominant role at low roughness, whereas roughness effects prevailed at higher roughness levels. These findings underscore the simultaneous importance of fluid rheology, surface geometry, and impact conditions in describing droplet dynamics on spherical surfaces and pave the way for future studies involving superhydrophobic and superhydrophilic coatings as well as complex rheological behaviors.

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Journal of Solid and Fluid Mechanics
Volume 16, Issue 3
July and August 2026
Pages 297-313

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