Contactless viscosity measurement by oscillations of gas-levitated drops

A recently demonstrated aerodynamic levitation technique is used to perform contactless viscosity measurements. Classical models dealing with free oscillations of droplets without gravity cannot correctly describe the correspondence between damping coefficient and viscosity. An energetic approach taking into account the shape of the drop, and the velocity field of the liquid inside the drop, is introduced, leading to good agreement between experimental measurements and known viscosities of glycerol-water mixtures. Nonlinear effects are also investigated and experimental results are compared with the theory of anharmonic oscillations.