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Measurements of the Flowfield Interaction Between Tandem CylindersThis paper presents the most recent measurements from an ongoing investigation of the unsteady wake interference between a pair of circular cylinders in tandem. The purpose of this investigation is to help build an in-depth experimental database for this canonical flow configuration that embodies the effects of component interaction in landing gear noise. This new set of measurements augments the previous database at the primary Reynolds number (based on tunnel speed and cylinder diameter) of 1.66 105 in four important respects. First, better circumferential resolution of surface pressure fluctuations is obtained via cylinder "clocking". Second, higher resolution particle image velocimetry measurements of the shear layer separating from the cylinders are achieved. Third, the effects of simultaneous boundary layer trips along both the front and rear cylinders, versus front cylinder alone in the previous measurements, are studied. Lastly, on-surface and off-surface characteristics of unsteady flow near the "critical" cylinder spacing, wherein the flow switches intermittently between two states that are characteristic of lower and higher spacings, are examined. This critical spacing occurs in the middle of a relatively sudden change in the drag of either cylinder and is characterized by a loud intermittent noise and a flow behavior that randomly transitions between shear layer attachment to the rear cylinder and constant shedding and rollup in front of it. Analysis of this bistable flow state reveals much larger spanwise correlation lengths of surface pressure fluctuations than those at larger and smaller values of the cylinder spacing.
Document ID
20090020435
Acquisition Source
Langley Research Center
Document Type
Conference Paper
Authors
Neuhart, Dan H. (NASA Langley Research Center Hampton, VA, United States)
Jenkins, Luther N. (NASA Langley Research Center Hampton, VA, United States)
Choudhari, Meelan M. (NASA Langley Research Center Hampton, VA, United States)
Khorrami, Mehdi R. (NASA Langley Research Center Hampton, VA, United States)
Date Acquired
August 24, 2013
Publication Date
May 11, 2009
Subject Category
Aerodynamics
Report/Patent Number
LF99-7906
Meeting Information
Meeting: 15th AIAA/CEAS Aeroacoustics Conference
Location: Miami, FL
Country: United States
Start Date: May 11, 2009
End Date: May 13, 2009
Sponsors: National Oceanic and Atmospheric Administraion, American Inst. of Aeronautics and Astronautics
Funding Number(s)
WBS: WBS 561581.02.08.07.18.02
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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