A new method for simultaneous measurement of surface tension and viscosity

Abstract

A new method for the simultaneous mesurement of the surface tension and viscosity of a liquid was developed by combining the principle of the oscillating drop method with a microgravity environment. This new method can be used in an ordinary laboratory. A droplet falls for 1.5 m in approximately 0.55 s. During this short period, the surface oscillation of the droplet is recorded by two high speed line sensors equipped with a laser backlight and cylindrical lenses. The recording speed and resolution of the line sensors are 84000 line/s and 2048 pixels, respectively. The laser backlight forms a shadow of the droplet, and each of the cylindrical lenses makes the shadow into be a line, allowing the maximum diameter to be precisely measured by a line sensor. Before focusing the laser column to a line, it was split into two columns and each of them is forcused into a different line in order to determine the changes in the diameters in two right-angled directions. The measured oscillations show only a single peak for the n = 2 mode in the Fourier spectrum. This fact guarantees that the surface oscillation is almost ideal, and the simple equations for a spherical droplet can be used without any corrections.