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Based on the immersed boundary concept that the border may be constructed by feedback force, a numerical simulation is carried out by modifying previous inner fluid treatment and incorporating it with non-equidistant grid. Flow around two elongated rectangles in tandem arrangement is computed in the range of Reynolds numbers from 200 to 103. Results indicate that when the Reynolds number is in the range 200–300, a vortex shedding of front rectangle is under control of two separated shear layers. The vortex between the two rectangles belongs to Karman type, which is hindered by small spacings thus symmetric vortices are formed. Shielding effects is mainly reflected by the phenomenon that mean drag coefficients of the rear rectangle is smaller than the front one. At the critical spacing ratio, a vortex sheet between the two rectangles is fully established. The mean drag coefficient also has a jump at this spacing ratio, which is still less than that of the front rectangle. In this phase, as Reynolds number increases, the vortex regime, the jump and the critical spacing all become minimized. When Re=400, the vortex shedding of front rectangle is characterized by an impinging-shear-layer, and thw drag coefficient is no longer a regular oscillation. After that as Reynolds number rises, an impinging-shear-layer is established gradually. More vortices on the surface are produced by flow separation of the front rectangle, which leads to a less magnitude of wake vortex. Shielding effect will disappear at this time. A fluctuation impact on the rear rectangle is induced by drastic vortex shedding from the front rectangle. But proper spacing between the two rectangles can make the drag coefficient of the rear rectangle jump, which is larger than that of the front rectangle.
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Keywords:
- immersed boundary concept /
- two elongated rectangular in tandem arrangement /
- shielding effects /
- critical spacing
[1] Chang J H, Liu H T, Liu M B, Su T X 2012 Acta Phys. Sin. 61 4704 (in Chinese) [常建忠, 刘汉涛, 刘谋斌, 苏铁熊 2012 物理学报 61 4704]
[2] Guo W B, Wang N C, Shi B C, Guo Z L 2003 Chin. Phys. 12 67
[3] Igarashi T 1981 Bulletin of JSME 188 323
[4] Slaouti A, Stansby P K 1992 J. of Fluids & Struct 6 641
[5] Meneghini J R, Saltara F, Siqueira C L R, Ferrari Jr. J A 2001 J. of Fluids & Struct 15 327
[6] Chen S Q, Huang Z P, Shen J H, Gu M 2001 Journal of Tong-ji University. 29 320 (in Chinese) [陈素琴, 黄自萍, 沈建华, 顾明. 2001 同济大学学报 29 320]
[7] Liu C H, Chen J M 2002 J. Wind Eng. Ind. Aerodyn. 90 1019
[8] Wen B H, Liu H Y, Zhang C Y, Wang Q 2009 Chin. Phys. B 18 4353
[9] Kang X Y, Ji Y P, Liu D H, Jin Y J 2008 Chin. Phys. B 17 1041
[10] Saiki E M, Biringen S 1996 J of Comput Phys 123 450
[11] Li C W, Wang L L 2004 Int. J. Numer. Meth. Fluids 46 85
[12] Fadlun E A, Verzicco R, Orlandi P, Mohd-Yusof 2000 J. of Comput. Phys. 161 35
[13] Gong Z X, Lu C J, Huang H X 2007 Chinese Quarterly of Mechanics 28 353 (in Chinese) [宫兆新, 鲁传敬, 黄华雄 2007 力学季刊 28 353]
[14] Zou L Y, Bai J S, Li B Y, Tan D W, Li P, Liu C L 2008 Chin. Phys. B 17 1034
[15] Nakamura Y, Ohya Y, Tsuruta H 1991 J. of Fluid Mech. 222 437
[16] Nakamura Y, Ohya Y, Ozono S, Nakayama R 1996 J. Wind Eng. Ind. Aerodyn. 65 301
[17] Ohya Y, Nakamura Y, Ozono S, Tsuruta H 1992 J. of Fluid Mech. 236 445
[18] Su Y M, Cui T, Yan D J, Zhao J X, Ju L 2012 Journal of Wuhan University of Technology 34 52 (in Chinese) [苏玉民, 崔桐, 闫岱俊, 赵金鑫, 鞠磊 2012 武汉理工大学学报 34 52]
[19] Berrone S, Garbero V, Marro M 2011 Computers & Fluids 42 92
[20] Liu S Y, Ge Y J 2013 Proceedings of the 12th Americas Conference on Wind Engineering, Seattle, USA, June 16-20, 2013 p2457
[21] Ohya Y, Okajima A, Hayashi M 1989 Encyclopedia of Fluid Mechanics 8 322
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[1] Chang J H, Liu H T, Liu M B, Su T X 2012 Acta Phys. Sin. 61 4704 (in Chinese) [常建忠, 刘汉涛, 刘谋斌, 苏铁熊 2012 物理学报 61 4704]
[2] Guo W B, Wang N C, Shi B C, Guo Z L 2003 Chin. Phys. 12 67
[3] Igarashi T 1981 Bulletin of JSME 188 323
[4] Slaouti A, Stansby P K 1992 J. of Fluids & Struct 6 641
[5] Meneghini J R, Saltara F, Siqueira C L R, Ferrari Jr. J A 2001 J. of Fluids & Struct 15 327
[6] Chen S Q, Huang Z P, Shen J H, Gu M 2001 Journal of Tong-ji University. 29 320 (in Chinese) [陈素琴, 黄自萍, 沈建华, 顾明. 2001 同济大学学报 29 320]
[7] Liu C H, Chen J M 2002 J. Wind Eng. Ind. Aerodyn. 90 1019
[8] Wen B H, Liu H Y, Zhang C Y, Wang Q 2009 Chin. Phys. B 18 4353
[9] Kang X Y, Ji Y P, Liu D H, Jin Y J 2008 Chin. Phys. B 17 1041
[10] Saiki E M, Biringen S 1996 J of Comput Phys 123 450
[11] Li C W, Wang L L 2004 Int. J. Numer. Meth. Fluids 46 85
[12] Fadlun E A, Verzicco R, Orlandi P, Mohd-Yusof 2000 J. of Comput. Phys. 161 35
[13] Gong Z X, Lu C J, Huang H X 2007 Chinese Quarterly of Mechanics 28 353 (in Chinese) [宫兆新, 鲁传敬, 黄华雄 2007 力学季刊 28 353]
[14] Zou L Y, Bai J S, Li B Y, Tan D W, Li P, Liu C L 2008 Chin. Phys. B 17 1034
[15] Nakamura Y, Ohya Y, Tsuruta H 1991 J. of Fluid Mech. 222 437
[16] Nakamura Y, Ohya Y, Ozono S, Nakayama R 1996 J. Wind Eng. Ind. Aerodyn. 65 301
[17] Ohya Y, Nakamura Y, Ozono S, Tsuruta H 1992 J. of Fluid Mech. 236 445
[18] Su Y M, Cui T, Yan D J, Zhao J X, Ju L 2012 Journal of Wuhan University of Technology 34 52 (in Chinese) [苏玉民, 崔桐, 闫岱俊, 赵金鑫, 鞠磊 2012 武汉理工大学学报 34 52]
[19] Berrone S, Garbero V, Marro M 2011 Computers & Fluids 42 92
[20] Liu S Y, Ge Y J 2013 Proceedings of the 12th Americas Conference on Wind Engineering, Seattle, USA, June 16-20, 2013 p2457
[21] Ohya Y, Okajima A, Hayashi M 1989 Encyclopedia of Fluid Mechanics 8 322
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