Validating ground-based aerodynamic levitation surface tension measurements through a study on Al₂O₃

The surface tension of a molten sample can be evaluated based on its resonant frequency with various levitation techniques. Under a 1-G condition, the use of levitation forces to counteract gravity will cause the levitated sample's resonant frequency to differ from that under microgravity. A mathematical relationship to correct for this deviation is not available for a sample levitated with aerodynamic levitation (ADL), which raises issues on the validity of surface tension measurements done with ADL. In this study, we compared the surface tension of molten Al₂O₃ obtained using the front tracking (FT) simulation method, the drop-bounce method with ADL, and the oscillating drop method with ADL. The drop-bounce method simulates microgravity by allowing the sample to free-fall over a period of tens of milliseconds. Based on the results of this comparison, we determined that the surface tension of molten materials measured with ground-based ADL with the oscillating drop method, calculated using the resonant frequency of the l=2 m=0 mode, only shows a small deviation from that obtained under microgravity.