Principal Investigator Merton Flemings
The purpose of this investigation is to use the unique attributes of microgravity to demonstrate a containerless technique for measuring the viscosity and surface tension of reactive and highly undercooled liquid metals, such as zirconium, steels, and glass forming alloys. The accurate determination of the thermophysical properties of liquid materials is important for fundamental and practical reasons, including verification of atomistic models of the liquid state, nucleation studies in phase transition, and modeling of materials processing operations.
In this experiment, a sample is positioned using electromagnetic levitation coils and melted by induced currents. The sample is then deformed by a pulsed magnetic force, creating surface oscillations. Using high-speed video recording and digital image analysis, the deformation of the sample over time can be analyzed using Fourier analysis to determine the frequency and decay of these oscillations, which allows the surface tension and viscosity of the sample to be determined.
When preparing for our experiments on the STS-83 and STS-94 shuttle missions, the main focus of the project was a combined approach of comprehensive mathematical modeling and earthbound experiments aimed at developing the methodology to run the experiments in space.
Successful experimental campaigns were conducted during the NASA space shuttle missions: STS-83 (short, only 1-week duration due to problems with the orbiter) and STS-94 (full reflight mission in July 1997). A very significant amount of experimental data was collected on viscosity and surface tension measurements of metallic and glass-forming materials. The preliminary analysis of the data demonstrates the containerless technique to perform these kinds of measurements. It is expected that the analysis of the data will also allow us to determine the critical Reynolds number for laminar transition in levitated droplets.
Current focus is to extend this technique to other materials systems with more industrial relevance. In addition, we are addressing the study of various fundamental fluid flow issues involved in electromagnetic levitated droplets, such as laminar flow transition and davitation induced nucleation.