Shallow Cavity Flow Tone Experiments: Onset of Locked-On States

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Fully turbulent inflow past a shallow cavity is investigated for the configuration of an axisymmetric cavity mounted in a pipe. Emphasis is on conditions giving rise to coherent oscillations, which can lead to locked-on states of flow tones in the pipe-cavity system. Unsteady surface pressure measurements are interpreted using three-dimensional representations of amplitude-frequency-inflow velocity; these representations are constructed for a range of cavity depth. Assessment of these data involves a variety of approaches. Evaluation of pressure gradients on plan views of the three-dimensional representations allows extraction of the frequencies of the instability (Strouhal) modes of the cavity oscillation. These frequency ... continued below

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21010 Kilobytes pages

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Rockwell, D.; Lin, J. C.; Oshkai, P.; Reiss, M. & Pollack, M. September 5, 2000.

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  • Lockheed Martin
    Publisher Info: Lockheed Martin Corporation, Schenectady, NY 12301 (United States)
    Place of Publication: Schenectady, New York

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Description

Fully turbulent inflow past a shallow cavity is investigated for the configuration of an axisymmetric cavity mounted in a pipe. Emphasis is on conditions giving rise to coherent oscillations, which can lead to locked-on states of flow tones in the pipe-cavity system. Unsteady surface pressure measurements are interpreted using three-dimensional representations of amplitude-frequency-inflow velocity; these representations are constructed for a range of cavity depth. Assessment of these data involves a variety of approaches. Evaluation of pressure gradients on plan views of the three-dimensional representations allows extraction of the frequencies of the instability (Strouhal) modes of the cavity oscillation. These frequency components are correlated with traditional models originally formulated for cavities in a free-stream. In addition, they are normalized using two length scales; inflow boundary-layer thickness and pipe diameter. These scales are consistent with those employed for the hydrodynamic instability of the separated shear layer, and are linked to the large-scale mode of the shear layer oscillation, which occurs at relatively long cavity length. In fact, a simple scaling based on pipe diameter can correlate the frequencies of the dominant peaks over a range of cavity depth. The foregoing considerations provide evidence that pronounced flow tones can be generated from a fully-turbulent inflow at very low Mach number, including the limiting case of fully-developed turbulent flow in a pipe. These tones can arise even for the extreme case of a cavity having a length over an order of magnitude longer than its depth. Suppression of tones is generally achieved if the cavity is sufficiently shallow.

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21010 Kilobytes pages

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OSTI as DE00821945

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  • Other Information: PBD: 5 Sep 2000

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  • Report No.: LM-00K072
  • Grant Number: AC12-00SN39357
  • DOI: 10.2172/821945 | External Link
  • Office of Scientific & Technical Information Report Number: 821945
  • Archival Resource Key: ark:/67531/metadc786648

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  • September 5, 2000

Added to The UNT Digital Library

  • Dec. 3, 2015, 9:30 a.m.

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  • April 28, 2016, 9:43 p.m.

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Rockwell, D.; Lin, J. C.; Oshkai, P.; Reiss, M. & Pollack, M. Shallow Cavity Flow Tone Experiments: Onset of Locked-On States, report, September 5, 2000; Schenectady, New York. (digital.library.unt.edu/ark:/67531/metadc786648/: accessed October 17, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.