Contactless viscosity measurement by a gas film levitated droplet technique

A recently demonstrated aerodynamic levitation technique is used to perform contactless viscosity measurements. The dynamic response of a perturbed levitating droplet is presented. Classical model dealing with free oscillations and damping of droplets without gravity cannot correctly describe the correspondence between measured damping coefficient and viscosity. An energetic approach taking into account the flattened shape of the drop, the particular boundary conditions imposed by the set-up, and the velocity field of the liquid inside the drop, is introduced, leading to good agreement between experimental measurements and known viscosities of calibrated liquids. The set-up has been used to perform contactless viscosity measurement on metallic alloys in the semi-solid state (Cu-Ag, 1100 K).