Abstract
In this study, instantaneous and time-averaged flow structures downstream of the sharp-edged single and two and three side-by-side square cylinders (SCs) immersed in a uniform open channel water flow were studied by a technique of particle image velocimetry (PIV). Experimental results of wake flow structures were presented for gap ratios (G/D) in the range of 1.0�G/D�3.0 for Reynolds number values of 1050, 2450 and 3400. Flow structures depending on the square cylinder (SC) configurations and Reynolds number were discussed. It has been found that the development of the vortex shedding as well as the flow structure were substantially altered for side-by-side SCs comparing to the single SC. Asymmetrical and biased wake structures were observed because of the jet- like flow between the SCs for two SCs cases for the gap ratio less than 2.0. Depending on the gap spacing between the SCs, the interaction results of time- averaged vorticity, velocity vector field, Reynolds stress correlations 2 U v' u' and streamline patterns in the wake region form a distinguished flow structure. Strouhal numbers for the single square cylinder for 1050�Re�3400 are found in the range of 0.12-0.13. The present results have supported the previous works by providing detailed quantitative experimental information with PIV in the wake region of the SC and might be helpful for validation of numerical studies and designers.
Highlights
The subject of single, two or multiple bluff-body flows owing to interactions of flow and solid structure has been attracted a great deal of attention, recently
The wake region accommodates velocity vectors V with very small magnitude in the downstream region of the square cylinders (SCs), which are the source of small-scale secondary vortices, as seen in the instantaneous flow patterns row in Figures 2 and 3
This study aims to provide an experimental systematic study of the flow behind single, two and side-by-side square cylinders
Summary
The subject of single, two or multiple bluff-body flows owing to interactions of flow and solid structure has been attracted a great deal of attention, recently. One of the main features of these bluff body flow configurations is a periodic force loading in streamwise and vertical directions due to the pressure variations on the cylinder surface caused by periodic vortex shedding. When more than one square cylinder (SC) are placed in a uniform flow, the flow characteristics such as surface pressure, drag coefficient and vortex-shedding frequency are completely different from the case of single SC depending on the arrangement of the gap ratio G/D of the SCs and Reynolds number. The flow structure around two or three SCs displays a very complicated flow patterns due to the
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