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 osc illations of droplets without gravity cannot correctly describe the corresp ondence between damping coefficient and viscosity. An energetic approach ta king into account the shape of the drop, and the velocity field of the liqu id inside the drop, is introduced, leading to good agreement between experi mental measurements and known viscosities of glycerol-water mixtures. Nonli near effects are also investigated and experimental results are compared wi th the theory of anharmonic oscillations.