Experimental research on dynamic characteristics of viscous droplets impacting rough solid surfaces at different temperatures

In view of different factors that influence dynamic behavior of a droplet impacting a solid surface, high-speed photography technology was used to capture oscillation processes and splash forms after changing seven kinds of physical properties, droplets impacting different roughness and temperature walls, and with different velocities and sizes. A physical model was established, and the theoretical value correlation of maximum spreading factor was derived to compare the theoretical analysis with experimental results. The effects of viscosity, surface tension, impact velocity, diameter of droplet, roughness, and temperature of the substrates on movement characteristics during the droplet’s impact on the wall surface were investigated. As the research indicates, the rebound and oscillatory phenomena of the fluid become more obvious with an increase in surface tension, and viscous force restricts the spreading of droplets. The higher the impact velocity, the greater the spreading factor at the same time, and the more pronounced the splashing phenomenon will be. The growth rate of maximum spreading factor (βmax) increases at first and then decreases with increasing initial diameter (d0) of the droplets. The smaller the d0, the more consistent the experimental results with the analytical solutions. The equilibrium contact angle (θe) of the droplet increases with surface roughness (Ra), whereas the surface wettability degrades. θe decreases with rising wall temperature. The increase of Ra promotes the “finger-like edge” and the splash motion of droplets; moreover, the critical velocity of splash declines with Ra. The optimum temperature (Tc) of a droplet impacting the high-temperature wall reduces with a decrease of Re. Furthermore, the greater the difference between wall temperature and Tc, the more significantly βmax changes. Droplet spreading is hindered on the low-temperature wall, and the lower Re is, the smaller the decrease in amplitude of βmax with dropping wall temperature.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author