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 引用本文: 唐聃, 戴绍仕, 谷慧群, Bassam A. Younis. 曲面边界黏性绕流的湍流模型改进方法研究. 力学学报, 2024, 56(1): 58-69.
Tang Dan, Dai Shaoshi, Gu Huiqun, Bassam A. Younis. Improvement of a turbulence model for viscous flow over curved surfaces. Chinese Journal of Theoretical and Applied Mechanics, 2024, 56(1): 58-69.
 Citation: Tang Dan, Dai Shaoshi, Gu Huiqun, Bassam A. Younis. Improvement of a turbulence model for viscous flow over curved surfaces. Chinese Journal of Theoretical and Applied Mechanics, 2024, 56(1): 58-69.

## IMPROVEMENT OF A TURBULENCE MODEL FOR VISCOUS FLOW OVER CURVED SURFACES

• 摘要: 多尺度旋涡现象广泛地存在于工程领域的湍流中. 研究湍流的重要方法是大涡模拟, 但大涡模拟中的过度耗散问题是曲面边界、多尺度旋涡模拟所面临的主要困难. 为了克服过度耗散的缺陷, 使大曲率曲面边界的多尺度涡流脉动特性预报更准确, 文章采用正则化变分多尺度模型(RVM)改进了壁面自适应涡黏模型(WALE)中的亚格子模型, 并采用C++语言在OpenFOAM开源平台实现了计算代码编译. 文章以经典圆柱黏性绕流作为曲面边界黏性绕流的代表, 讨论了改进的大涡模型(MWALE)中滤波算子对亚临界雷诺数( Re = 4.0 \times 10^4 )圆柱绕流大规模、多尺度旋涡发放预测能力的影响. 数值计算结果表明: 改进的大涡模型对滤波算子阶数(n)敏感. 四阶滤波算子(n = 2)能准确地预报圆柱壁面的平均涡量及尾流瞬时涡量分布、再循环旋涡长度和速度剖面, 而二阶滤波算子(n = 1)无法准确地预测分离区和尾流区内脉动速度剖面, 因此在强压力梯度区四阶滤波算子预测的压力分布、脉动升阻力与实验结果吻合的更好, 能更准确地捕捉到多尺度旋涡结构.

Abstract: Multiscale vortex flows are found in many engineering applications. The principal method for studying turbulence is large eddy simulation (LES). However, the over-dissipative behavior of LES poses a special difficulty in the simulation of multiscale vortex flows that occur over strongly-curved surfaces. In order to overcome the over-dissipation behavior, and make the prediction of fluctuating characteristics with multiscale vortex flow over curved surfaces more accurate, the regularized variational model (RVM) was adopted to improve the sub-grid scale model in the wall-adapting local eddy-viscosity model (WALE), leading to the development of the modified wall-adapting local eddy-viscosity model (MWALE). The modification was implemented in C++ language in the OpenFOAM software. Using the classical case of viscous flow around cylinder, the influence of filter operator on predicting performance of massive and multiscale vortex shedding at subcritical Reynolds number ( Re = 4.0 \times 10^4 ) is considered in this paper. Computational results show that the improved model is sensitive to the order (n) of the filtering operator. Fourth-order filter operator (n = 2) can accurately predict the distribution of mean vorticity on the cylinder surface, and the instantaneous vorticity in the wake. Also well predicted are the recirculation zone length and the mean-velocity profiles. However, the second-order filter operator (n = 1) cannot accurately predict the fluctuating velocity profiles in the reversed-flow and the wake region. It is found that the predicted pressure distribution in the strong pressure-gradient region, the fluctuating lift and drag forces and the multiscale vortex structures using the fourth-order filter operator are in close agreement with the experimental data.

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