Gravity impact on viscosity measurements by aerodynamic levitation

Abstract

This publication deals with the estimation of viscosity of liquid metals. It is proposed to discuss the possibility to determine this parameter during aerodynamic levitation experiments performed in ground laboratory. Once in liquid state, metallic sample is submitted to acoustic waves through the levitation gas making it oscillate and deform. A high speed camera records the radial periodic deformation during the relaxation period, meaning when incident waves stop. The evolutions of the sample radius over time are extracted from records and compared with analytical model based on the damped oscillator. The estimation of viscosity is performed by inverse method and leads to overestimated values by comparison with expected values. Then, numerical simulations (CFD) including or not levitation gas and gravity are performed to show the impact of gravity during measurements. New viscosity estimations show that the damped oscillation model (Lamb’s theory) as it is classically used is not valid in aerodynamic levitation due to the influence of both gravity and gas.