WER-13: Characteristics of wakes downstream of circular cylinders and 12-sided cylinders, as determined by Wind Tunnel tests
Snyder, Melvin H.
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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.
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.
In the public domain. Prepared for NASA - Lewis Research Center under Grant NSG-3277. General Release Date: January 1981