﻿ PANS方法在双圆柱绕流数值模拟中的性能分析
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PANS方法在双圆柱绕流数值模拟中的性能分析

Property assessment of PANS method for numerical simulation of flow around tandem cylinders
DU Ruofan, YAN Chao , LUO Dahai
School of Aeronautic Science and Engineering, Beijing University of Aeronautics and Astronautics, Beijing 100191, China
Abstract:Partially averaged Navier-Stokes (PANS) method derived from the traditional Reynolds averaged Navier-Stokes (RANS) methods by introducing controlling parameter into original RANS equations to modify these equations, is one kind of hybrid methods which can effectively simulate the separated turbulent flows. Computational results of tandem cylinders using PANS method based on Menter shear stress transport (SST) turbulence model were presented in this investigation. The flow structures around tandem cylinders were analyzed and the accuracy and reliability of PANS method were also verified. Moreover, the influence of the model parameter on numerical results was investigated and the performance of different types of PANS methods was assessed. Studies show that the unresolved-to-total ratio of turbulence kinetic energy has significant effects on the numerical results, and taking this parameter as a constant value throughout the whole computational domain can hardly tackle the complex flow problem. Furthermore, the parameter is made to change along with flow physical information and the local grid scale. The variable fk PANS method agrees well with the results from SST detached-eddy simulation (DES) and the experimental measurements, suggesting strong adaptability to complex turbulence simulation.
Key words: tandem cylinders     turbulence     partially averaged Navier-Stokes (PANS)     unresolved-to-total ratio of turbulence kinetic energy     computational fluid dynamics (CFD)

1 计算方法

PANS方法以RANS方程为模板,本文采用的PANS方法基于两方程SST(Shear Stress Transport)模式,原始SST模式方程[17]

2 计算结果与分析

 图 1 双圆柱构型的xOy截面示意图 Fig. 1 Schematic diagram of xOy plane for tandem cylinders configuration

 图 2 双圆柱构型计算网格示意图 Fig. 2 Schematic diagram of computational grid for tandem cylinders configuration

 图 3 不同方法瞬时展向涡量云图 Fig. 3 Contours of instantaneous spanwise vortices from different methods

 图 4 BART PIV实验结果[13] Fig. 4 Experimental results from BART PIV[13]

 图 5 双圆柱壁面平均压力系数分布 Fig. 5 Mean pressure coefficient distribution of surfaces of both cylinders

 图 6 中心线流向平均速度分布 Fig. 6 Mean streamwise velocity distribution at centerline

 图 7 中心线二维湍动能分布 Fig. 7 2D turbulence kinetic energy distribution at centerline

 图 8 可变fk PANS方法计算中fk的分布 Fig. 8 Distribution of fk for variable fk PANS method
3 结 论

1) 对于统一fk方法,模型参数fk对计算结果有显著影响.随着fk取值增大,PANS方法模化更多的湍流尺度,展向流动受到抑制,小尺度涡减少,流动结构趋于粗糙,流动更多呈现出二维特征.与实验结果相比,fk=0.3、0.5所得结果流动分离推迟,分离区偏小,湍流脉动偏弱.而fk=0.1所得结果分离提前,分离区偏大,脉动过强,与实验同样存在明显差异.故对于双圆柱绕流,统一fk方法适应性不足,难以处理该复杂流动问题,无法给出令人满意的结果.

2) 可变fk方法将模型参数fk与当地流动信息和网格尺度信息关联起来,构造fk在计算域内的分布函数,自动调节fk在不同流动区域的取值.计算结果表明,可变fk方法具有求解小尺度湍流结构的能力,所得涡结构丰富,流场正确合理.通过流场平均量及脉动量的对比分析,可变fk方法与SST DES计算结果及实验结果均吻合较好,相较于统一fk方法体现出了较为明显的优势,是一种具有工程应用前景的新型RANS/LES混合方法.

3) 下一步研究工作中,考虑改进及构造新型的fk分布函数,以更为准确地模拟复杂湍流问题,并通过对方法更加深入地考察评估,将其进一步推向工程应用.

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#### 文章信息

DU Ruofan, YAN Chao, LUO Dahai
PANS方法在双圆柱绕流数值模拟中的性能分析
Property assessment of PANS method for numerical simulation of flow around tandem cylinders

Journal of Beijing University of Aeronautics and Astronsutics, 2015, 41(8): 1374-1380.
http://dx.doi.org/10.13700/j.bh.1001-5965.2014.0589