Collision dynamics of SDS solution drops on a smooth wood substrate: Role of surface tension

Drop impact has been widely studied as it plays a key role in numerous scientific and industrial applications. Despite an extensive trove of literature, only a limited number of studies have investigated the behavior of liquid drops impinging on polished wood. Subsequently, to better ascertain how surface tension (ST) influences the drop impact behavior on smooth wood surfaces, the impingement of SDS solution drops on a polished Diospyros crassiflora substrate (R-q = 60 mu m) was investigated in this study. The results revealed a distinct absence of recoil amongst the impinging SDS solution drops (gamma = 72-40 mN/m) when the maximum wetting diameter was reached. However, a decrease in ST did correspond to the formation of more prominent finger-like projections and an increase in the extent up to which it spread on the wood surface. Interestingly, similar behavior was observed amongst impinging water/SDS solution drops when the impact velocity was increased (0.44-2.9 m/s); thus, indicating that in general, the drop impact behavior of SDS solution drops on wood was significantly dependent on its Weber number. A decrease in the ST also corresponded to an increase in the critical Weber number or a decrease in the critical impact height (H-c). An increase in the impact height (>H-c) was marked by an increase in the number of emitted droplets. The volume and propagation velocities of these droplets were dependent on the time (after impact) at which they were formed. (C) 2020 Elsevier B.V. All rights reserved.