Stability of Flow around Two Rectangular Cylinders in Tandem

R. Gnatowskaa, J. Sobczykb, W. Wodziakb aCzestochowa University of Technology, Department of Thermal Machinery, 42-201 Częstochowa, Poland bStrata Mechanics Research Institute, Polish Academy of Sciences, Reymonta St. 27, 30-059 Krakow, Poland

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The experimental study with the use of particle image velocimetry (PIV) has been conducted to investigate the stability of flow around two identical square cylinders in tandem arrangement at a different Reynolds numbers. The important study parameter was the displacement of the downstream cylinder with velocity in range from Vc=0.01 to 0.09 m/s. Effect of gradually increasing and decreasing the spacing between the cylinders, in the inter-cylinder spacing ratio from 2 to 9, on a stability of flow was investigated. The unstable flow is connected with two discontinuous jumps in the flow patterns and occurs when the spacing between cylinders varies in two ways. The changes in the flow modes were determined based on the time histories of velocity fluctuations analysed independently in number of points located in different regions of the measuring section. The impact of the downstream cylinder velocity and the Reynolds number on the lower and the upper spacing limits of the unstable modes was presented and discussed. The results show that the unstable flow modes are highly dependent on the combined values of free-stream Reynolds numbers ReD and the downstream cylinder displacement velocity Vc.

DOI:10.12693/APhysPolA.138.295 topics: square cylinders, tandem arrangement, PIV, fluid flow, vortex shedding