The thermal expansion coefficients, structure factors, and viscosities of twenty-five equilibrium and supercooled metallic liquids have been measured using an electrostatic levitation (ESL) facility. The structure factor was measured at the Advanced Photon Source, Argonne, using the ESL. A clear connection between liquid fragility and structural and volumetric changes at high temperatures is established; the observed changes are larger for the more fragile liquids. It is also demonstrated that the fragility of metallic liquids is determined to a large extent by the cohesive energy and is, therefore, predictable. These results are expected to provide useful guidance in the future design of metallic glasses.

The effect of fluid flow on crystal nucleation in supercooled liquids is not well understood. The variable density and temperature gradients in the liquid make it difficult to study this under terrestrial gravity conditions. Nucleation experiments were therefore made in a microgravity environment using the Electromagnetic Levitation Facility on the International Space Station on a bulk glass-forming Zr57Cu15.4Ni12.6Al10Nb5 (Vit106), as well as Cu50Zr50 and the quasicrystal-forming Ti39.5Zr39.5Ni21 liquids. The maximum supercooling temperatures for each alloy were measured as a function of controlled stirring by applying various combinations of radio-frequency positioner and heater voltages to the water-cooled copper coils. The flow patterns were simulated from the known parameters for the coil and the levitated samples. The maximum nucleation temperatures increased systematically with increased fluid flow in the liquids for Vit106, but stayed nearly unchanged for the other two. These results are consistent with the predictions from the Coupled-Flux model for nucleation.

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Unsteady aerodynamics has been difficult to measure since the beginning days of wind tunnel testing. Distributed dynamic loads have been determined by using special (dynamic) transducers that measure pressure fluctuations at a few to several hundred points on a wind tunnel model and then integrating the pressure fluctuations over a specified area. Typical data acquisition systems that capture the pressure fluctuations record at rates up to 50,000 samples/channel/second and can generate many terabytes of raw data. Processing the large amount of data generated typically cannot be accomplished during wind tunnel tests, so selected data are processed for evaluation during testing. Another area of concern over the last several decades has been weapons bay acoustics and their effect on store separation. The U.S. Air Force (USAF) needs to understand the aerodynamics of payloads separating from aircraft to support weapons system design and certification. Customers to the Air Force such as Lockheed Martin Aeronautics Company have been developing computational fluid dynamics (CFD) models of stores separation in order to reduce the amount of wind tunnel and flight testing required for the certification process on each weapon and platform. Currently CFD validation can only be performed at point locations where dynamic pressure transducers are installed. Engineers at the Arnold Engineering Development Complex (AEDC) have utilized a steady-state pressure-sensitive paint (PSP) capability in the Propulsion Wind Tunnel (PWT) 16T to acquire surface pressure data on wind tunnel models. A logical next step was to extend this capability to measure fluctuating pressures with PSP. Innovative Scientific Solutions, Inc. (ISSI) has developed a fast-responding PSP under USAF and NASA Phase II small business innovation research (SBIR) grants that can detect pressure fluctuations up to 20kHz. This was made possible by new developments in high-speed camera technology and brighter light emitting diode (LED) technology. However, the test section in 16T places the test article approximately 8-11 feet away from cameras and LEDs. Detecting the fluorescence emitted by the fast PSP with exposure times in the hundreds of micro-seconds would be a challenge. In support of the Air-Delivered Weapon Certification Cost Reduction program, ISSI was awarded a grant to demonstrate the fast PSP capability in 16T with AEDC and Lockheed as partners. ISSI would provide the technical assistance, equipment and PSP, Lockheed would perform CFD computations and provide the test article, and AEDC would develop data acquisition and image processing software and perform the wind tunnel testing in 16T. Power spectral density (PSD) comparisons are made between the fast PSP and conventional dynamic pressure transducers. In addition, the complete spatial distribution of the sound pressure level (SPL) at selected frequencies are presented to aid understanding of the data and provide additional insight. Proper Orthogonal Decomposition is applied to the data for identification o...

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