FLOW-VISUALIZATION OF A TWO SIDE-BY-SIDE CYLINDER WAKE

2002 ◽  
Vol 9 (2-3) ◽  
pp. 16 ◽  
Author(s):  
Zhiwen WANG ◽  
Y. Zhou ◽  
Hui Li
Keyword(s):  
Flow Visualization ◽  
Cylinder Wake

scholarly journals Rotary oscillation control of a cylinder wake

1991 ◽  
Vol 224 ◽  
pp. 77-90 ◽  
Author(s):  
P. T. Tokumaru ◽  
P. E. Dimotakis
Keyword(s):  
Flow Visualization ◽  
Free Stream ◽  
Reynolds Numbers ◽  
Uniform Flow ◽  
Circular Cylinders ◽  
Cylinder Wake ◽  
Oscillation Control ◽  
Displacement Thickness ◽  
Cylinder Drag

Exploratory experiments have been performed on circular cylinders executing forced rotary oscillations in a steady uniform flow. Flow visualization and wake profile measurements at moderate Reynolds numbers have shown that a considerable amount of control can be exerted over the structure of the wake by such means. In particular, a large increase, or decrease, in the resulting displacement thickness, estimated cylinder drag, and associated mixing with the free stream can be achieved, depending on the frequency and amplitude of oscillation.

The finite-length square cylinder near wake

2009 ◽  
Vol 638 ◽  
pp. 453-490 ◽  
Author(s):  
H. F. WANG ◽  
Y. ZHOU
Keyword(s):  
Flow Visualization ◽  
Flow Structure ◽  
Finite Length ◽  
Laser Doppler Anemometry ◽  
Three Dimensional ◽  
Width Ratio ◽  
Stream Velocity ◽  
Cylinder Wake ◽  
Square Cylinder ◽  
Near Wake

This paper reports an experimental investigation of the near wake of a finite-length square cylinder, with one end mounted on a flat plate and the other free. The cylinder aspect ratio or height-to-width ratio H/d ranges from 3 to 7. Measurements were carried out mainly in a closed-loop low-speed wind tunnel at a Reynolds number Red, based on d and the free-stream velocity of 9300 using hot-wire anemometry, laser Doppler anemometry and particle image velocimetry (PIV). The planar PIV measurements were performed in the three orthogonal planes of the three-dimensional cylinder wake, along with flow visualization conducted simultaneously in two orthogonal planes (Red = 221). Three types of vortices, i.e. the tip, base and spanwise vortices were observed and the near wake is characterized by the interactions of these vortices. Both flow visualization and two-point correlation point to an inherent connection between the three types of vortices. A model is proposed for the three-dimensional flow structure based on the present measurements, which is distinct from previously proposed models. The instantaneous flow structure around the cylinder is arch-type, regardless of H/d, consisting of two spanwise vortical ‘legs’, one on each side of the cylinder, and their connection or ‘bridge’ near the free end. Both tip and base vortices are the streamwise projections of the arch-type structure in the (y, z) plane, associated with the free-end downwash flow and upwash flow from the wall, respectively. Other issues such as the topological characteristics, spatial arrangement and interactions among the vortical structures are also addressed.

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