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Technical Brief

Introducing Perturbations into Turbulent Wall-Bounded Flow With Arrays of Long TiO2 Nanowires

[+] Author and Article Information
Henry A. Sodano

Materials Science and Engineering, and Mechanical
and Aerospace Engineering,
University of Florida,
Gainesville, FL 32611

Aneesh Koka

Mechanical and Aerospace Engineering,
University of Florida,
Gainesville, FL 32611

Christopher R. Guskey, T. Michael Seigler

Department of Mechanical Engineering,
University of Kentucky,
Lexington, KY 40506

Sean C. C. Bailey

Department of Mechanical Engineering,
University of Kentucky,
Lexington, KY 40506
e-mail: sean.bailey@uky.edu

1Corresponding author.

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received January 30, 2014; final manuscript received April 7, 2014; published online September 10, 2014. Assoc. Editor: Prashanta Dutta.

J. Fluids Eng 137(2), 024501 (Sep 10, 2014) (4 pages) Paper No: FE-14-1050; doi: 10.1115/1.4027432 History: Received January 30, 2014; Revised April 07, 2014

A currently unexplored mechanical application of nanowires is near-wall active flow manipulation, with potential uses mixing and filtering chemicals, enhancing convective heat transfer, and reducing drag. Here, we present experimental evidence that it is possible to introduce persistent perturbations into turbulent flow with active nanowires. A TiO2 nanowire array was fabricated and installed in the bounding wall of a turbulent channel flow, and the array was oscillated by external actuation. Measurements indicated that the array increased turbulent kinetic energy throughout the entire wall layer. These findings suggest that dynamically actuated nanowires can potentially be used to implement near-wall flow control.

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Figures

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Fig. 1

Characterization of TiO2 nanowire arrays. (a), (b) Scanning electron microscope image of the hydrothermally grown ultralong sodium titanate nanowires used for the flow interaction experiments. (c) XRD pattern from the as-synthesized TiO2 nanowires showing rutile phase following the ion exchange and calcination process. R denotes rutile TiO2 peaks (JCPDS #65-0191) Ti denotes titanium peaks (JCPDS #65-3362). (d) HRTEM image of the TiO2 nanowire with the inset showing the single crystal diffraction pattern.

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Fig. 2

Schematic of experimental setup. Geometry of the experiment showing placement of nanowire surfaced, coordinate system and position of measuring probe and active surface installation relative to the oncoming flow in the wind tunnel.

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Fig. 3

Frequency spectra and kinetic energy. (a) Measured frequency spectra at y+ = 15 with spectra shifted vertically by four orders of magnitude for each consecutive Reτ to increase figure clarity. Black line is actuated wafer, gray line is un-actuated wafer. (b) Energy added to the flow by the nanowire motion.

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Fig. 4

Comparison before and after abrasion of nanowire arrays. (a) Comparison of measured frequency spectra at y+ = 15. (b) Energy added to the flow between PZT wafer with nanowires and without nanowires.

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