Energy dissipation and maximum solidification-limited spreading of impacting drops

The debate over the mechanism continues that restricts spreading of drop impacts on cold substrates, when lamella simultaneously spreads and solidifies. Despite its importance in controlling footprint during drop deposition in spray coating and additive manufacturing, we are in a lack of model that enables precise prediction of maximum spreading diameters for freezing-induced contact line pinning for drop impacts. Here, we provide experimental investigations involving hexadecane drop impacts on cold solid substrates at temperatures below the liquid freezing point, across a range of impact velocities. We introduce an effective boundary layer thickness to estimate dissipation within the shear layer (Thiévenaz et al., 2020) to include both viscosity and phase-change. As the lamella extends over the solidified volume at the contact line region (Gielen et al., 2020; Lolla et al., 2022), we propose an additional dissipative friction at proximity to the contact line and incorporated this friction factor into our prognostic model based on an energetic approach to predict maximum solidification-limited spreading ratio in We-Ste parametric space. Non-dimensional number Di is proposed to assess relative dominance to hinder spreading between basal and lateral dissipation, suggesting dissipation at contact line may not be negligible.