Viscous Force Retards Initial Droplet Spreading
2017
Shi, Lichun | Liu, Yang | Lü, Hongyu | Meng, Yonggang | Hu, Guoqing | Tian, Yu
A droplet could spread on a solid substrate within several milliseconds, and be divided into two stages: a fast inertial stage and a subsequent slow viscous stage. The effects of inertia and viscosity on spreading are presented with Ohnesorge number. A small Ohnesorge number corresponds to an initial inertial spreading. In this study, spreading experiments were carried out with a time resolution of 1 μs. Results disclose that the viscous force could retard droplet spreading at the beginning of liquid/solid surface contact, even with an Ohnesorge number smaller than 0.1. According to simulation results, the viscous retardation could be ascribed to the real high local shear rate along the contact line at the spreading front. These results provide a new insight on droplet spreading dynamics and proposes, where exists a third viscous-inertial stage during the initial droplets spreading process.
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