用POD方法研究有限长正方形棱柱尾流的双稳态现象  

On the bistable phenomenon of a finite length square cylinder wake with POD method

作　　者：王汉封[1,2] 徐胜金[3] 

机构地区：[1]中南大学土木工程学院,湖南长沙410075 [2]中南大学高速铁路建造技术国家工程实验室,湖南长沙410075 [3]清华大学航空航天学院,北京100871

出　　处：《空气动力学学报》2014年第6期827-833,共7页Acta Aerodynamica Sinica

基　　金：国家自然科学基金资助项目(51108468;11472312)

摘　　要：利用PIV对高宽比为7的有限长正方形棱柱尾流和二维方柱尾流进行了测量。实验中雷诺数为9300。对流场进行了本征正交分解(POD),并分析了各阶模态对湍动能的贡献。基于瞬态流场重建中各阶模态的系数,比较了有限长棱柱尾流和二维柱体尾流的瞬态流动特性。结果表明:在二维柱体尾流中,代表着卡门涡街的1、2阶模态对湍动能的贡献占支配地位,达到了73.6%,而在有限长柱体尾流中,1、2阶模态的贡献仅为45.9%。后者的尾流中存在两种典型的流动形态:一种是1、2阶模态占主导的卡门涡街形态,类似于二维棱柱尾流;另一种是3阶或更高阶模态占主导的对称形态。The near wake of a 2D square cylinder and that of a finite length square cylinder with the as-pect ratio of 7 was measured by PIV.The Reynolds number based on free stream oncoming flow and cylinder width is 9300.Proper orthogonal decomposition （POD）was performed to analysis the contributions of each mode on turbulence kinetic energy （TKE）.Instantaneous flow properties were compared between the near wake of finite length and 2D square cylinders,utilizing the coefficients of POD modes for flow reconstruc-tion.It was found that,in 2D cylinder wake,the first 2 POD modes,which represent the Karman vortex shedding,dominated the near wake and contributed 73.6% of total TKE;while in the finite length square cylinder wake,the TKE contribution from the first two modes was only 45.9%.There were two typical in-stantaneous flow status occur in the finite length cylinder wake：one was the status of Karman vortex shed-ding dominated by the first two POD modes,similar to that in a 2D cylinder wake;the other was symmetri-cal flow status which was dominated by the third and/or other higher POD modes.

关 键 词：有限长柱体 尾流 PIV POD 双稳态现象 

分 类 号：TB126[理学—工程力学]