Micro-Scale Turbulence Measurements Using a Nano-Scale Thermal Anemometry Probe (NSTAP)

This grant will facilitate study of turbulence at small length scales in high Reynolds number flows using a novel instrument developed by the PI. Turbulence at high Reynolds numbers is characteristic of many industrial applications, including pipe flows for transporting oil and gas, aircraft, ships and submarines. These extreme regimes have historically been inaccessible due to the paucity of appropriate experimental facilities and the lack of suitable characterization techniques. However, the combination of state-of-the-art facilities with the recent development of a nanoscale thermal anemometry probe (NSTAP) at Princeton, opens up the opportunity to study these technologically important flows. The research focuses on three unresolved topics in fluid mechanics; the analysis and development of turbulence intensity similarity formulations, the analysis and development of the spectral scaling regions, and the verification of the Kolmogorov turbulence theories. The Superpipe and HRTF facilities developed at Princeton make possible the study of high Reynolds number turbulence, but the spatial resolution of currently available instrumentation is inadequate to study the full range of scales present in the flow. The ability to study turbulence on the small (1-10 micron) size scale is now made possible by the successful development of the NSTAP. The probe consists of a platinum nanowire fabricated using standard nanofabrication techniques. Continued development of the probe, pushes toward even smaller sizes, with the aim of producing and characterizing a wire (10 - 50 nm wide x 1-10 microns long). Such a sensing wire will have the unique capability of measuring fluid flow on spatial and temporal scales two orders of magnitude smaller than can currently be studied with existing instrumentation. The success of this work will have broad implications for researchers in fluid mechanics, leading to an improved understanding of turbulent flows. The approaches in developing NSTAP will also open the door to a deeper understanding of the materials science and physics underlying the formation and response of a free standing metallic nanowire. For instance, this study will generate knowledge on the mechanical and electronic properties metallic nanowires, which may be used in other applications such as on-chip interconnects. Effects such as electromigration, recrystallization, and intrinsic stress evolution that occur due to fabrication techniques and current flow in the wire are important to researchers in other areas and will be examined over the course of this study. This project will greatly benefit from close collaborations among a diverse blend of student and faculty researchers in fluid mechanics and materials science enabling both types of specialists to learn about the other's field. The implementation of the NSTAP for these studies will educate students through the practices of both nanofabrication and turbulence measurements. The research will be readily accessible for undergraduate participation through term projects and summer research experience.

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Princeton University
United States
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