Vortex shedding from a rectangular prism and a circular cylinder placed vertically in a turbulent boundary layer

Abstract

Measurements of the vortex-shedding frequency behind a vertical rectangular prism and a vertical circular cylinder attached to a plane wall are correlated with the characteristics of the smooth-wall turbulent boundary layer in which they are immersed. Experimental data were collected to investigate the effects of (i) the aspect ratio of these bodies and (ii) the boundary-layer characteristics on the vortex-shedding frequency. The Strouhal number for the rectangular prism and the circular cylinder, defined by S = fcw/U0 and fcd/U0 respectively, was found to be expressed by a power function of the aspect ratio h/w (or h/d). Here fc is the vortex-shedding frequency, U0 is the free-stream velocity, h is the height, w is the width and d is the diameter. As the aspect ratio is reduced, the type of vortex shedding behind each of the two bodies was found to change from the Karman-type vortex to the arch-type vortex at the aspect ratio of 2·0 for the rectangular prism and 2·5 for the circular cylinder.

Hypersonic Viscous Flow Over Large Roughness Elements

“…Figure 12 shows a snapshot of instantaneous vorticity distribution near the hump for M=0.3 and M=0.8. Analogous vortex shedding phenomenon has been observed in low-speed experiments as well as computations involving 3D roughness elements [12,13]. On the other hand, while there exist computations of 2D separating flows without humps where spontaneous shedding has been noted in the past [14,15], we were unable to find experiments involving 2D humps wherein similar behavior has been noted.…”

“…For example, in ref. [12], it was observed and measured experimentally that flapping and strong vortex motion can originate from both the top and the side faces of the rectangular prism, resulting in sinuous or varicose modes in the wake region. In contrast, flow physics around large roughness elements immersed in supersonic or hypersonic boundary layers is relatively less understood due to limitations in instrumentations and flow visualization techniques.…”

Study of flow around model of cooling tower by means of 2D Particle Image Velocimetry measurement

“…For later research, this part could be even more interesting: according to [4], shedding of vortices changes from Kármán asymmetric type to symmetric arch type at a geometrical aspect ratio of an object (cylinder) of 2.5; as the aspect ratio of our measured object varies from 1.3 to 2.54, the narrowest area of it could be measured with respect to this fact. …”

Effect of Additional Structure on Effective Stack Height of Gas Dispersion in Atmosphere

“…However, Catro and Robins [10] and Snyder and Castro [11] suggest that the Reynolds number dependency for flows over sharp-edged obstacles such as the reactor at the BWR site is weak. On the other hand, a flow region behind two-dimensional circular cylinder strongly depends on the Reynolds number, but the wake behind finite cylinders of small aspect ratio of cylinder height L to diameter D (L/D = 1-2) like the PWR site is symmetric and the Reynolds number dependency for flows is weak [12].…”