Experimental Study on the Flow Around Two Tandem Cylinders with Unequal Diameters  

作　　者：GAO Yangyang ETIENNE Stephane WANG Xikun TAN Soon Keat 

机构地区：[1]Ocean College, Zhejiang University [2]State Key Laboratory of Satellite Ocean Environment Dynamics,Second Institute of Oceanography, SOA [3]Mechanical Engineering Department, Ecole Polytechnique de Montreal [4]Maritime Research Centre and School of Civil and Environmental Engineering, Nanyang Technological University

出　　处：《Journal of Ocean University of China》2014年第5期761-770,共10页中国海洋大学学报（英文版）

基　　金：supported by the Zhejiang Provincial Natural Science Foundation of China under Grant No. LY14E090009;State Key Laboratory of Satellite Ocean Environment Dynamics (Second Institute of Oceanography, SOA), State Key Laboratory of Fluid Power Transmission and Control (GZKF-201310);State Key Laboratory of Ocean Engineering, China. The National Research Foundation of Singapore (NRF-CRP5-2009-01);Maritime Research Centre and Nanyang Environment and Water Research Institute, Nanyang Technological University, Singapore, is acknowledged

摘　　要：In this paper, flow around two circular cylinders in tandem arrangement with unequal diameters has been investigated using the particle image velocimetry technique(PIV) in a water channel. The upstream to downstream diameter ratio was kept constant at d/D = 2/3, the centre-to-centre distance was varied from 1.2D to 5D and the Reynolds number was varied from 1200 to 4800. The flow characteristics were analyzed through ensemble-averaged patterns of velocity, vorticity, normalized Reynolds stress contours and streamlines. Based on ensemble-averaged and instantaneous flow fields, different flow patterns, including single-wakeshedding at small spacing ratio, bi-stable flow behavior(alternating behavior of reattachment and vortex shedding) at intermediate spacing ratio and co-shedding pattern at large spacing ratio were observed. The effects of Reynolds number and the centre-to-centre spacing ratio on flow patterns and turbulent characteristics were also investigated. It was found that the diameter ratio appears to have a certain effect on the flow patterns at intermediate spacing ratios, where the reattachment of shear layer depends on the lateral width of the wake flow in the lee of the upstream cylinder. Extensive discussion on the distributions of Reynolds stress and turbulent kinetic energy was presented.In this paper, flow around two circular cylinders in tandem arrangement with unequal diameters has been investigated using the particle image velocimetry technique（PIV） in a water channel. The upstream to downstream diameter ratio was kept constant at d/D = 2/3, the centre-to-centre distance was varied from 1.2D to 5D and the Reynolds number was varied from 1200 to 4800. The flow characteristics were analyzed through ensemble-averaged patterns of velocity, vorticity, normalized Reynolds stress contours and streamlines. Based on ensemble-averaged and instantaneous flow fields, different flow patterns, including single-wakeshedding at small spacing ratio, bi-stable flow behavior（alternating behavior of reattachment and vortex shedding） at intermediate spacing ratio and co-shedding pattern at large spacing ratio were observed. The effects of Reynolds number and the centre-to-centre spacing ratio on flow patterns and turbulent characteristics were also investigated. It was found that the diameter ratio appears to have a certain effect on the flow patterns at intermediate spacing ratios, where the reattachment of shear layer depends on the lateral width of the wake flow in the lee of the upstream cylinder. Extensive discussion on the distributions of Reynolds stress and turbulent kinetic energy was presented.

关 键 词：tandem cylinders with unequal diameters PIV flow patterns Reynolds stress distribution 

分 类 号：P731.2[天文地球—海洋科学]