Numerical Simulation of three-dimensional flow around a circular cylinder of finite length
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摘要:
目的 为探究有限长圆柱绕流的流动机理和特性， 方法 采用大涡模拟（LES）数值模型并结合涡识别方法，对三维有限长圆柱绕流进行数值模拟，并对有限长圆柱绕流进行验证和分析。 结果 模拟结果表明，有限长圆柱回流区相对较短，自由端的下洗作用会扰乱卡门涡街，导致阻力系数损失；相对于固定壁面，自由端面对顺流向速度影响更大；自由端面"蘑菇"涡成对出现，且存在2个流动源点；有限长圆柱流场存在更明显的三维特性，阻力系数更小；圆柱自由端后存在梢涡，圆柱与固定壁面交界处存在"马蹄"涡。 结论 所得结果可对有限长圆柱的流动特性进行相对全面的描述，对于理解和研究有限长圆柱绕流机理具有一定的参考价值。 Abstract:Objectives In this paper, in order to study the flow characteristics and mechanism of three-dimensional flow around a circular cylinder of finite length, Methods a numerical simulation using a Large Eddy Simulation (LES) and vortex structural classification technology is carried out, and the accuracy of the simulation is proven. Results When analyzing the flow field, it is found that the length of the recirculation zone is smaller for a circular cylinder of finite length. In addition, the downstream from the free end can suppress the common phenomenon of Karman-Vortex-Street which leads to a loss of drag-coefficient. Compared with the fixed wall at the bottom, the free end surface has a higher influence on the onstream-wise velocity. The 'mushroom' vortex appears in pairs and two original points exist on the free end. The circular cylinder of finite length appears to be strongly three-dimensional with a lower drag-coefficient. Moreover, there is a tip vortex behind the free end and a horseshoe vortex in the cylinder-wall junction. Conclusions The results of this paper give a relatively comprehensive description of the flow characteristics of a circular cylinder of finite length, and can provide useful references for relevant research. -
图 4 有限长和无限长圆柱顺流向速度ux及压力系数Cp分布
Figure 4. Distribution of streamwise velocity ux and pressure coefficient Cp for FC and IFC
图 5 有限长和无限长圆柱的升力系数、阻力系数时域分布
Figure 5. Distribution of the time-dependent lift and drag coefficient for FC and IFC
图 7 有限和无限长圆柱顺流向速度ux沿z方向的分布
Figure 7. Distribution of streamwise velocity ux around z axis for FC and
图 8 有限长圆柱Q准则涡量等值线分布
Figure 8. Distribution of iso-contours for vorticity of FC according to Q-criterion
图 11 Q准则涡量等值面图（Q=6）
Figure 11. Vortical structures revealed by isosurface of the Q-criterion(Q=6)
表 1 数值计算结果与文献实验结果的对比
Table 1. Comparison of numerical simulation and experimental results provided by the literatures
算例 网格数 Re AR ${{\bar C}_{\rm{d}}} $ Clrms St SGS IFC0 509 800 3.9×103 - 1.078 0.124 0.21 SM IFC1 619 500 3.9×103 - 1.026 0.116 0.21 SM IFC2 619 500 3.9×103 - 1.141 0.126 0.22 DSM IFC3 800 000 3.9×103 - 1.028 0.116 0.21 SM Sim1 - 3.9×103 - 0.99 0.11 0.21 - FC0 1 000 000 3.9×103 π 0.746 0.063 0.16 SM FC1 1 822 972 3.9×103 π 0.784 0.053 0.11 SM FC2 1 822 972 3.9×103 π 0.832 0.058 0.11 DSM FC3 2 400 000 3.9×103 π 0.782 0.050 0.11 SM EXP1 - 3.2×104 2 0.78 - - - EXP2 - 4.7×104 2 0.73 - 0.122 - EXP3 - 2.9×103 π 0.77 - - - 
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