Effects of Longitudinal Alignments on the Time-Mean Flow Structures of Side-by-Side Circular Cylinders of Diameter Ratio Two

Abstract:

The time-averaged flow characteristics in the regions upstream and downstream of the side-by-side cylinders of diameter ratio two, arranged at different longitudinal alignments and two gap ratios, are studied via particle image velocimetry (PIV). It is found that the locations of forward stagnation point of the large and the small cylinders do change with the longitudinal alignments. Upstream of the large cylinder, the streamwise variations of U* are nearly independent of the longitudinal alignment for both T*=1.5 and 1.0. However, upstream of the small cylinder, the streamwise variations of U* indeed depend on T*. Upstream of the small cylinder, the streamwise variations of V* are strongly affected by T* and, the largest magnitude of V* occurs at CLA for both T*=1.5 and T*=1.0. Also, the locations of the largest magnitude of V* move closer to the small cylinder as the T* reduces. For different T* and L*, the flow rate (or the averaged velocity through the gap) and the gap orientation will be changed at the same Reynolds number (Re=1000). The effect of pressure difference across the gap may be overwhelmed or be counterbalanced by that of the gap orientation leading to quite different flow structures in the downstream region of the cylinder couples. The effects of longitudinal alignment are to (1) change the forward stagnation points of the large and the small cylinders; (2) modify the region of mutual interaction between two wakes. (3) As S* reduces, the gap orientation takes the dominance over the pressure difference across the gap to switch the gap flow so that the wide-wake is formed behind the small cylinder especially for T*=1.0 and TEA.

• Periodical: Defect and Diffusion Forum (Volume 370)
• Pages: 29-40
• DOI: https://doi.org/10.4028/www.scientific.net/DDF.370.29
• Online since: January 2017
• Authors: Sheng Yung Tseng, Shang Wen Hsu, Cheng Hsiung Kuo
• Keywords: Different Diameter, Gap Orientation, Longitudinal Alignment, PIV, Side-By-Side Cylinders

References

[1] M.M. Alam, M. Moriya, H. Sakamoto, Aerodynamic characteristics of two side-by-side circular cylinders and application of wavelet analysis on the switching phenomenon, J. Fluids and Structures 18 (2003) 325-346.

DOI: 10.1016/j.jfluidstructs.2003.07.005

[2] C. Brun, D. Tenchine, E.J. Hopfinger, Role of the shear layer instability in the near wake behavior of two side-by-side circular cylinders, Experiments in Fluids, 36 (2004) 334-343.

DOI: 10.1007/s00348-003-0726-6

[3] Y.Y. Gao, D.Y. Yui, S. Tan, X Wang. and Z. Hao, Experimental study on the near wake behind two side-by-side cylinders of unequal diameters, Fluid Dynamics Research, 42 (2010) 055509.

DOI: 10.1088/0169-5983/42/5/055509

[4] IDTVISION, User Manual, ProVISION-XS, software release 3. 11 (2014).

[5] R.D. Keane, R.J. Adrian, Optimization of particle image velocimeters Part I: double pulsed systems, Meas. Sci. Technol. 1(6) (1990) 1202–1215.

DOI: 10.1088/0957-0233/1/11/013

[6] H.J. Kim and P.A. Durbin, Investigation of the flow between a pair of circular cylinders in the flopping regime, J Fluid Mech. 192 (1988) 431-448.

DOI: 10.1017/s0022112088002769

[7] N.W.M. Ko, P.T.Y. Wong, R.C.K. Leung, Interaction of flow structures within bistable flow behind two circular cylinders of different diameters, Experimental Thermal and Fluid Science 12 (1996) 33-44.

DOI: 10.1016/0894-1777(95)00065-8

[8] C.H. Kuo, G.H. Yen and C. Lin, Visualization of flow structure behind two side-by-side circular cylinders, The Third Asian Symposium on Visualization, May, Chiba, Japan, (1994) 186-192.

[9] K.M. Lam, P.T.Y. Wong, N.W.M. Ko, Interaction of flows behind two circular cylinders of different diameters in side-by-side arrangement, Experimental Thermal and Fluid Science, 7 (1993) 189-201.

DOI: 10.1016/0894-1777(93)90002-z

[10] J.J. Miau, G.Y. Wang, J.H. Chou, Intermittent switching of gap flow downstream of two flat plates Arranged side by side, J. Fluids and Structures 6 (1992) 563-582.

DOI: 10.1016/0889-9746(92)90019-y

[11] A. Michalke, On spatially growing disturbances in an inviscid shear layer, J. of Fluid Mech. 23 (1965) 521-544.

DOI: 10.1017/s0022112065001520

[12] C.H.K. Williamson , Evolution of a single wake behind a pair of bluff bodies, J. Fluid Mech. 159 (1985) 1-18.

DOI: 10.1017/s002211208500307x

[13] S. Xu, Y. Zhou, R.M.C. So, Reynolds number effects on the flow structures behind two side-by-side cylinders, Phys Fluid 15 (2003) 1214-1219.

DOI: 10.1063/1.1561614

[14] M.M. Zdravkovich, Review of flow interference between two circular cylinders in various arrangements, J Fluid Engineering 99 (1977) 618-633.

DOI: 10.1115/1.3448871

[15] R. Wille, H. Fernholz, Report on the first European Mechanics Colloquium, on the Coanda effect, J. Fluid Mech. 23 (1965) 801-819.

DOI: 10.1017/s0022112065001702