Stokes' dream: Measurement of fluid viscosity from the attenuation of capillary waves

The determination of viscosity from the attenuation of capillary waves was first suggested by Stokes more than a century ago. At the time, it was not practical to measure the attenuation of surface waves with the requisite precision to render the method useful. We describe a noncontact method for measuring the wavelength and amplitude of single-frequency capillary waves to obtain reliable values of the surface tension and viscosity. The attenuation data for several glycerin-water mixtures are used to obtain the viscosity as a function of glycerin concentration. For a wide range of viscosity, the method yields results that are in good agreement with the most reliable published data. (C) 2010 American Association of Physics Teachers. [DOI: 10.1119/1.3467887]