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WER-13: Characteristics of wakes downstream of circular cylinders and 12-sided cylinders, as determined by Wind Tunnel tests
Snyder, Melvin H. Wentz, W.H.
Snyder, Melvin H.
Wentz, W.H.
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WER-13
Adobe PDF, 13.38 MB
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Issue Date
1981-01
Type
Technical report
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Keywords
Wakes,Aerodynamics
Subjects (LCSH)
Citation
Melvin H. Snyder, W.H. Wentz. Characteristics of Wakes downstream of circular cylinders and 12-sided cylinders, as determined by Wind Tunnel tests. Wind Energy Report no.13. Wichita State University. Center for Energy Studies, 1981, 101 p.
Abstract
To obtain models of the near-field wakes behind cylinders of the types used
as support structures for wind turbines, wind tunnel tests were conducted in the
Walter Beech Memorial Wind Tunnel of Wichita State University. The tests were
surveys of wakes downstream of circular cylinders and of 12-sided cylinders.
Surveys were conducted at stations ranging from 20 to 90 downstream of the
cylinder centerlines.
Among the results of the survey are the following:
The wake downstream of a cylinder has three characteristics which may affect a
wind turbine blade passing through the wake :
a. A velocity deficit compared to the freestream wind.
b. Random turbulence of wide frequency range and moderate strength,
c. low frequency (less than 100 Hz) periodic vibrations.
The velocity deficit profile for the near-field is significantly different than
published far-field profiles. Turbulence associated with the mixing has highest
values on both sides of the wake centerline, where ~ values are highest. The
magnitude of turbulence is about the same for 12-sided cylinders as for circular
cylinders. The separation point and geometry of the wake of a l2-sided cylinder
is independent of Reynolds number (unlike a circular cylinder). Rounding the
corners of a l2-sided cylinder causes some dependence on the Reynolds number and
reduces the strength of the periodic motion. Spiral strakes on a circular
cylinder can eliminate the periodic motion of the wake--at the expense of increased
velocity deficit and turbulence of the wake.
Table of Contents
Description
In the public domain. Prepared for
NASA - Lewis Research Center
under Grant NSG-3277.
General Release Date: January 1981
Publisher
Wichita State University. Center for Energy Studies
Journal
Book Title
Series
Wind Energy Report;
;V.13
;V.13