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This study builds upon prior research by exploring droplet oscillation dynamics for surface tension determination using a drop-on-demand high-temperature droplet generator. Computational fluid dynamics (CFD) simulations were conducted to analyse frequency shifts over time, comparing two different materials with consistent results. The findings suggest potential for developing correction factors for oscillations with larger initial deformations. Additionally, frequency shifts relative to evolving aspect ratios of droplets starting with higher initial deformations were compared. Corrective measures can be applied, particularly beneficial for short-term measurements based on image analysis with minimal overall frequency shift. Slight asymmetry in oscillation with increasing aspect ratio could be accredited to droplet cross-sectional geometry or energy availability for returning prolate droplets to a spherical state. Experimental results indicated minimal frequency shift within a measurement duration of up to 40 ms, affirming the adequacy of using a fitted sine function without a time-dependent frequency term for overall frequency determination. A dimensionless criterion can be used to filter out unsuitable droplets. A temperature-dependent surface tension trend for AlCu10 alloy consistent with literature findings is introduced. [ABSTRACT FROM AUTHOR]

Rayleigh's equation has been widely used to determine surface tension from oscillating droplets. In this study, the use of a drop-on-demand droplet generator is proposed to create free-falling, oscillating, molten metal droplets for this purpose. To examine the applicability of the droplet generator, extensive numerical simulations in three and two-dimensions were performed. The effect of gravity, initial velocity and initial deformation on the frequency and pattern of the droplet oscillation was investigated. The use of this generator enables the creation of thousands of droplets in the course of a single experiment and the droplets have a much shorter exposure time to possible unwanted contaminations, due to a rapid measurement principle. Furthermore, the adjustable nozzle size of the generator provides flexibility in terms of droplet size, which affects the range of validity of Rayleigh's method. To validate the method, the surface tension of molten copper in an argon atmosphere was determined over a temperature range of 1400–1620 K. The determined linear relation is expressed as σ [mN m−1] = (1307 ± 98) − (0.22 ± 0.015) (T−1356) (T in K). [ABSTRACT FROM AUTHOR]