- 1. 哈尔滨工业大学（威海）船舶与海洋工程学院，山东威海
摘要: 研究湍流模拟方法对三维圆柱绕流数值模拟精度的影响，分别采用雷诺平均法（RANS）中的κ-ω模型、SST模型以及大涡模拟法（LES）对亚临界区内雷诺数Re=3 900时的三维圆柱绕流进行数值计算，分析了圆柱体表面的受力、圆柱后流场时均速度特性与瞬时涡量分布情况。结果表明，当流体流过圆柱表面时，圆柱表面出现的与流速方向相反的负压力差区域使流体从圆柱表面分离，引起了不稳定的周期性交替脱落的湍流涡泄，从而在圆柱表面产生周期性波动的升力，同时在圆柱后近流场区域形成回流区。研究还发现，LES法对圆柱体的受力以及流场时均速度特性的模拟效果要优于κ-ω模型与SST模型；相较于前人利用浸入边界法得到的模拟结果，LES法的模拟精度也有了较大提升；同样，通过对瞬时流场涡量等值线图的分析，并与已有的模拟结果进行对比，发现LES法不但可以从整体上表现出漩涡的周期性脱落，而且对流场中不同位置的、复杂的小尺度湍流涡泄也描述得非常细致，得到的自由分离剪切层长度与湍流涡泄的卷曲度更符合湍流涡泄的特征。所以，在亚临界区，LES法对湍流的模拟效果相对较好。
Analysis of three-dimensional numerical simulation methods for turbulent flow past circular cylinder
- 1. School of Naval Architecture and Ocean Engineering, Harbin Institute of Technology at Weihai, Weihai
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Abstract: Studying the influences of a turbulence simulation method on the accuracy of the three dimensional numerical simulation of the turbulent flow past a circular cylinder, this study is made in a subcritical region(Re=3900) by using κ-ω model, SST model, and large eddy simulation (LES), which are included in Reynolds average Navier-Stokes(RANS) . Analyses of the stress distribution on the surface of the cylinder, the time average velocity characteristics of the flow field and the instantaneous vorticity distribution of the flow field behind the cylinder have been done in the study. The analysis results show that the negative pressure difference on the surface of the cylinder, which is of opposite direction to the velocity when flow passes a circular cylinder, separates the fluid from the surface of the cylinder and causes unstable periodic turbulent vortex shedding, which resulted to the periodic fluctuation of the lift force on the cylindrical surface and a backflow zone behind the cylinder. Moreover, the simulation effect of the LES method on the stress distribution on the cylindrical surface and a time average velocity characteristics of the flow field are superior to κ-ω model and SST model. Compared with the simulation results of immersed boundary method used by DU Yuan-zheng, the simulation precision of the LES method also has greater improvement. Then based on the analysis of the iso-contour maps of the vorticity magnitude of the flow field and comparing them with the existing simulation results, the LES method can not only depict the periodic shedding vortices as a whole, but also describe the complex small scale turbulent vortex at different positions of the flow field meticulously. And the scale of the separated free-shear layers and the crimpness of the vortex are more in line with the characteristics of the turbulent vortex shedding. Finally, it came to the conclusion that the simulation effect of the LES method for the turbulent flow is relatively better than that of the κ-ω model and SST model in the subcritical region.