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WER-18: Further investigations of near-field wakes of circular and 12-sided cylinders and effects of shrouds and strakes
Snyder, Melvin H.
Snyder, Melvin H.
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WER-18
Adobe PDF, 13.29 MB
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Issue Date
1983-02
Type
Technical report
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Keywords
Wakes,Aerodynamics
Subjects (LCSH)
Citation
Melvin H. Snyder. Further investigations of near-field wakes of circular and 12-sided cylinders and effects of shrouds and strakes. Wind Energy Report no.18. Wichita State University, 1983-02, 123 p.
Abstract
Near-field physical characteristics of wakes
downstream of cylinders were determined in a wind tunnel .
Cylinders included a 12 - sided cylinder , a plane circular
cylinder, circular cylinders surrounded by shrouds of 46%
porosity and of 79% porosity, and the basic circular
cylinder with plane strakes and with perforated strakes
added . Characteristics measured included velocity deficit
of the air in the wake, the dominant frequency of the
periodic component of the wake vibration, and the level of
intensity of the general turbulence of the wake.
Conclusions revealed include the following : Both
circular cylinders and 12-sided cylinders have low velocity
wakes which have strong periodic motion . The chief factor
determining the nature of the wake of a circular cylinder
is the Reynolds number; supercritic~l Reynolds numbers
produce wakes which are smaller and less turbulent .
Geometry and orientation of the 12- sided cylinder strongly
affect the character of the wake with little sensitivity to
Reynolds number. The wake is marked by lower veloci ty ,
higher turbulence and stronger periodic motion than the
wake of a round cylinder .
The periodic motion may be attenuated by the use of
porous shrouds and strakes. These devices produce,
however, broader wakes with lower velocities and with more
extensive regions of reversed flow. The shrouds are
superior to the strakes; they are not sensitive to wind
direction as are the strakes.
Table of Contents
Description
In the public domain. Prepared for NASA - Lewis Research Center
under Grant NSG327. General Release Date: May, 1985
Publisher
Wichita State University
Journal
Book Title
Series
Wind Energy Report;
;no.18
;no.18