液滴衝突による液体粘度計測法

抄録

Viscosity of liquids is an important property determining flow characteristics such as shear stress caused by a flow, and elongation and dripping of films and drops. Conventional techniques determine liquid viscosity from shear stress acting in a capillary tube, on a vibrating plate, or on a rotating cylinder. The disadvantages of the methods are its relatively long measurement time and large amount of samples required, and more importantly, its inapplicability for coagulating liquids whose viscosity increases with time. Here we develop an original liquid viscosity measurement technique that employs a drop impact on a solid surface. The measurement principle is based on the energy budget: An impacting drop spreads on a solid surface due to kinetic energy which is on the surface converted to the viscous dissipation and the surface tension energy. We can therefore deduce the viscosity from the inertial, the surface tension force and the maximum spreading diameter. The simplicity of the present technique enables us to overcome the problems of the conventional methods. In experiments, we measured the viscosity of glycerol aqueous solution drops using a high-speed camera and a laser sensor. In conclusion, we revealed the uncertainty of the present technique is approximately 10 %, which was evaluated both by uncertainty analysis and by experimentally comparing the viscosity with the ones obtained with an Ostwald viscometer.