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Water-tunnel study of transition flow around circular cylindersThe recently reported phenomenon of asymmetric flow separation from a circular cylinder in the critical Reynolds number regime has been confirmed in a water-tunnel experiment. For the first time, an attempt was made to visualize the wake of the cylinder during the transition from subcritical to critical flow and to correlate the visualizations with lift and drag measurements. The occurrence of a dominant asymmetric-flow state was quite repeatable, both when increasing and decreasing the Reynolds number, resulting in a mean lift coefficient of C sub L approx 1.2 and a shift in the angle of the wake by about 12 deg. A distinctive step change in the drag and shedding frequency was also found to occur. A hysteresis was confirmed to exist in this region as the Reynolds number was cycled over the transition range. Both boundaries of the asymmetry appear to be supercritical bifurcations in the flow. The asymmetry was normally steady in the mean; however, there were instances when the direction of the asymmetry reversed and remained so for the duration of the Reynolds number sweep through this transition region. A second asymmetry was observed at a higher Reynolds number; however, the mean lift coefficient was much lower, and the direction of the asymmetry was not observed to reverse. Introducing a small local disturbance into the boundary layer was found to prevent the critical asymmetry from developing along the entire span of the cylinder.
Document ID
19840015538
Acquisition Source
Legacy CDMS
Document Type
Technical Memorandum (TM)
Authors
Almosnino, D. (NASA Ames Research Center Moffett Field, CA, United States)
Mcalister, K. W. (NASA Ames Research Center Moffett Field, CA, United States)
Date Acquired
September 4, 2013
Publication Date
May 1, 1984
Subject Category
Aerodynamics
Report/Patent Number
A-9606
AVSCOM-TM-84-A-1
NAS 1.15:85879
NASA-TM-85879
Accession Number
84N23606
Funding Number(s)
PROJECT: RTOP 505-31-21
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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