Spreading and arrest of a molten liquid on cold substrates.

Abstract

Understanding the spreading and solidification of liquids on cold solid surfaces is a problem of fundamental importance and general utility. The physics of nonisothermal spreading followed by phase change is still a mystery. The present work focuses on the dynamics and thermal characteristics of liquid drop spreading and their subsequent arrest due to freezing. The spreading of liquid is recorded, and the evolution of the liquid spreading diameter and liquid-solid contact angle is measured from the recordings of a high-speed digital camera. After the initiation of solidification, the liquid drops are pinned to the substrate, showing fixed footprints and contact angles. A physical hypothesis using scaling is provided to explain the relationship between the arrested base diameter (D*) and arrested contact angle (θ*) with respect to the Stefan number (Ste). The experimental observations of solidified drops on cold substrates corroborate the derived physical theory.