基于重叠网格与结构网格的圆柱绕流数值模拟

Numerical simulation of flow around a cylinder based on overset grids and structural grids

为研究重叠网格与结构网格在圆柱绕流数值模拟中的区别,以二维圆柱为例,利用有限元分析软件ANSYS 19.2中的DM与Mesh建立模型并划分重叠网格,利用ANSYS 19.2中的ICEM建立模型并划分结构网格。采用FLUENT 19.2中laminar模型模拟分析系统中的平均升力系数、平均阻力系数、斯特劳哈尔数St等流体动力特性。通过改变流体流速得到两种不同网格下各6组雷诺数Re,这6组雷诺数在60~160之间。结果表明:结构网格与重叠网格的St都随着Re的增加而增加,但相同雷诺数下重叠网格对应的St数值更大,St的增长速度更快;重叠网格与结构网格的平均升力系数与平均阻力系数随着Re的增加趋于稳定的速度都加快,但结构网格的平均升力系数与平均阻力系数趋于稳定的速度更快,且两种网格的平均升力系数与平均阻力系数趋于稳定速度的差距逐渐缩小,当Re=160时,两种网格的平均升力系数与平均阻力系数趋于稳定的速度几乎相同;当雷诺数在60~160之间时,采用重叠网格计算出来的斯特劳哈尔数比结构网格更加接近理论值;从升力功率谱密度分布曲线中可以看出,随着雷诺数的增加,两种网格下的频率逐渐变大,并且相同雷诺数下重叠网格的频率比结构网格大。

In order to study the difference between overset grids and structural grids in numerical simulation of flow around a cylinder,a two-dimensional cylinder is taken as an example,finite element analysis software ANSYS 19.2 DM is used to establish the model and divide the overset grids,and ICEM in ANSYS 19.2 is used to establish the model and divide the structural grids.The laminar model in FLUENT19.2 is used to simulate and analyze the aerodynamic characteristics of the system,such as the average lift coefficient,the average drag coefficient,and the Strauhal number(St).By changing the air velocity,six groups of Reynolds number(Re)are obtained in two different grids,which ranged from 60 to 160.Results obtained show that:(1)The St of bothstructural and overset grids increases with the increase of Re,but the St corresponding to the overlapping grids under Reynolds number is larger and the St grows faster.(2)Both the average lift coefficient and average drag coefficient of overset and structural grids tend to be stable with the increase of Re.The average lift coefficient and average drag coefficient of structural grids tend to be stable,but the speed is faster,and with the increase of Re,the difference between the stable speed of average lift coefficient and average drag coefficient of the two grids gradually become narrow.When Re=160,the stable speed of average lift coefficient and average drag coefficient of the two grids is almost the same.(3)When the Reynolds number is between 60 and 160,the Strouhal number calculated by overset grids is closer to the theoretical value than that by structured grids.(4)From the lifting power spectral density distribution curve,it can be seen that with the increase of Reynolds number,the frequency of the two grids increases gradually,and the frequency of overset grids is larger than that of structured grids under the same Reynolds number.