On the motion of Newtonian and non-Newtonian liquid drops

In the present study, the motion of Newtonian and non-Newtonian liquid drops has been investigated experimentally. In order to investigate the effect of bulk fluid on drops, we have used water and air, as two fluids with different properties, and various industrial and biological applications. Image processing is utilized to analyze the images obtained by a high speed camera. The research has been separated into two parts. The first part has been devoted to the experiments in which air is the bulk fluid, and the second is related to the experiment carried out in water. The range of Reynolds number is, approximately, 50 < Re < 500. The major concern of the present study is the size variation of drops and its effect on the drag coefficient. It is proved that the period of size variation of a drop does not vary with properties. Rheological aspects of the problem have also been considered. In air with small density and viscosity, addition of non-Newtonian characteristics to the fluid causes the behavior of the drop to undergo dramatic changes. However, in water, a denser and more viscous bulk fluid, the behavior of Newtonian and non-Newtonian drops (at least for shear thinning fluids) looks the same.