| 不同亚格子模型在亚声速槽道流大涡模拟中的应用对比 |
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| 作者姓名： | 洪正 叶正寅 |
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| 作者单位： | 西北工业大学航空学院，陕西西安 710072 |
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| 基金项目： | 国家自然科学基金11732013 |
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| 摘 要： | 湍流边界层流动是一种广泛存在于飞行器内部和外部的流动现象,是基础理论和模型验证的重要研究对象.能够捕捉大部分流动细节且计算量适中的大涡模拟(large-eddy simulation, LES)方法在湍流数值模拟中得到了越来越广泛的应用.文章基于格心有限差分方法,使用4阶紧致中心格式离散N-S方程无黏项,分别应用5种不同的亚格子(subgrid-scale, SGS)模型,即隐式, SM(Smagorinsky model), DSM(dynamic Smagorinsky model), WALE(wall-adapting local eddy-viscosity model)和CSM(coherent structures model),对Re=3 000, Ma=0.5的等温壁面槽道流动进行了大涡模拟研究.与实验值和直接数值模拟(direct numerical simulation, DNS)结果对比后发现,流场平均温度、平均密度等热力学量以及平均流向速度对亚格子模型不敏感,不适宜作为判断模型优劣的判据.亚格子模型在壁面附近的耗散越大,壁面摩擦速度以及阻力系数就越小.对于与速度相关的脉动量来说,不同模型得到的结果在壁面和脉动峰值附近误差比较大,中心线附近较小;显式模型结果在流向速度峰值处均高于参考值,而在展向和壁面法向速度脉动峰值处则均偏低.考虑显式的4种模型在壁面附近的涡黏系数分布, DSM和CSM曲线满足涡黏系数与无量纲壁面距离3次方成正比的分布规律, SM曲线斜率偏小而WALE曲线斜率偏大.
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| 关 键 词： | 槽道流 N-S方程 大涡模拟 格心有限差分法 亚格子模型 |
| 收稿时间： | 2018-12-20 |
Application of Different Subgrid-Scale Models used in Large-Eddy Simulation of Subsonic Channel Flow |
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| Authors: | HONG Zheng YE Zheng-yin |
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| Affiliation: | School of Aeronautics, Northwestern Polytechnical University, Xi'an 710072, China |
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| Abstract: | Turbulent boundary layer flow is a basic phenomenon that exists widely inside and outside the aircraft. This phenomenon is of primordial interest for fundamental research as well as for numerical modeling. Large-eddy simulation(LES) has been widely applied to simulate turbulent flow due to its ability to capture main flow details and moderate computational cost. Based on cell-centered finite difference method, the 4th-order compact center scheme was used to discretize convective Fluxes. Five different subgrid-scale(SGS) models were applied to simulate the isothermal-wall channel flow at Re = 3 000, Ma = 0.5, namely the implicit model, the Smagorinsky model(SM), the dynamic Smagorinsky model(DSM), the wall-adapting local eddy-viscosity model(WALE) and coherent structures model(CSM). Compared to experimental and direct numerical simulation(DNS) results, it's found that there is no evident discrepancy in mean temperature, mean density and mean streamwise velocity between different SGS models. These quantities, therefore, are not proper to distinguish SGS models. The greater dissipative the SGS model is, the smaller the wall friction velocity and friction coefficient are. As for fluctuating quantities associated with velocity, the error of results obtained by different models is larger near the wall and the peak, while smaller near the center line. Results from all explicit models are higher than reference value at the peak of fluctuating velocity in streamwise direction, while lower in spanwise and wall-normal directions. Considering eddy viscosity coefficient, DSM and CSM satisfy the relation that the eddy viscosity is proportional to the cube of dimensionless distance from the wall, and the slope of SM is smaller while the slope of WALE is larger. |
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| Keywords: | channel flow N-S equation large-eddy simulation cell-centered finite difference method subgrid-scale model |
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