圆柱绕流流场结构的大涡模拟研究

为进一步揭示绕流现象的形成机理,本文分别对处于层流稳态区、尾流过渡区、剪切层转换区Re分别为26、200、1.4×105的三种典型流态下的单圆柱绕流进行了二维数值模拟研究。Re为26时应用层流模型直接求解N-S方程,而Re分别为200、1.4×105时使用大涡模拟的方法进行计算。数值模拟很好地再现了稳定的涡旋结构、周期性交替脱落的卡门涡街结构、不规则的涡旋结构,在此基础上分析了尾流结构的基本特征及其压强分布规律、平均的流场特性、积分参数(如升力系数、阻力系数、斯特劳哈尔等),并与有关研究成果进行了对比。研究发现,采用不同流动介质时流场特性有所差异,空气为介质时的计算结果更符合实验的成果,而水为介质时计算结果偏差较大,这主要是由尾流涡旋产生的不合理负压造成的。

Large eddy simulation of the circular cylinder flow in different regimes

The present paper focuses on the analysis of two-dimensional flow past a circular cylinder in different regimes: laminar steady regime,wake-transition regime and shear-Layer transition regime with Reynolds number 26,200 and 1.4×10 5 respectively.When Re is 26,the laminar model is used to solve the N-S equation directly,and the large eddy simulation is applied to compute for Re=200 and Re=1.4×10 5.The simulation well reveals the structure of steady vortex,Karman vortex streets with periodic vortex shedding and irregular vortices.The basic characteristics and pressure distributions in wakes are analyzed,time averaged flow field and integral parameters,such as lift and drag coefficient,Strouhal number are compared with the related experiments.It is found that there are some different features when using different mediums to carry out calculation.When air is used,the results agree better with experimental results than that when water is used,these differences are mainly caused by unreasonable negative pressure.