Dynamic characteristics of a non-Newtonian impinging droplet on a heated copper surface

Abstract

This study experimentally investigates the dynamic behavior of a non-Newtonian droplet that impinges on a heated copper surface. The influence of Weber number and surface temperature on dynamic change of contact angle and spreading diameter was studied. The xanthan gum solutions with different particle concentrations were used for generating non-Newtonian droplets and a high-speed camera was utilized for capturing digital images in measuring dynamic contact angle and spreading diameter for different surface temperatures. It was found that even if the surface temperature increased, the maximum spreading diameters was nearly the same for each Weber number. However, the retraction rates of non-Newtonian droplets increased with Weber number, whereas those of Newtonian droplets remained constant. It is because of a drastic change in liquid viscosity with the surface temperature for non-Newtonian liquid. In addition, the shear viscosity of non-Newtonian droplet in the receding regime decreased much faster than that of Newtonian droplet.