LDV measurements of Newtonian and non-Newtonian open-surface swirling flow in a hydrodynamic mixer

The aim of this paper is to study the cyclone-like flow inside a hydrodynamic mixer experimentally, with a special emphasis on the differences in the flow field in the case of Newtonian and non-Newtonian fluids. The mixer consists a cylindrical body with conical bottom, in which two, tangentially entering fluid jets drive the rotating motion of the fluid body. The two fluids are (1) water and (2) a Carbopol solution obeying power-law rheology. The circumferential and axial velocity distributions were measured with the help of LDV for several fluid levels and driving flow rates. We show that in the case of water, the velocity distributions are qualitatively similar for several flow rates if the fluid height is kept constant. In the case of the power-law fluid, the measured velocity profiles show less generality.