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基于DUGKS的槽道湍流大涡模拟研究

LARGE EDDY SIMULATION OF TURBULENT CHANNEL FLOW USING DUGKS-LES

  • 摘要: 基于介观数值模拟方法的大涡模拟(large eddy simulation, LES)是研究湍流的重要手段之一. 离散统一气体动理学方法(discrete unified gas kinetic scheme, DUGKS)是一种相对较新的介观方法, 其作为湍流大涡模拟工具的研究还处于起步阶段. 文章通过耦合标准离壁Smagorinsky亚格子应力模型和Musker壁面模型, 实现了DUGKS-LES介观大涡模拟方法. 推导了在DUGKS中实现大涡模拟所需的有效总应力和修正分布函数非平衡态的关系式; 通过壁面函数逆求解壁面剪切应力时, 设计了可以保证收敛性的快速牛顿迭代法, 并利用逆问题的近似解进一步提高了迭代效率. 最后, 分别对摩擦雷诺数为180, 395和950的槽道湍流进行大涡模拟, 并与相关文献中介观大涡模拟方法的结果进行了比较. 结果表明, DUGKS-LES方法在准确性上具有优势, 以谱方法模拟结果为基准, 流向速度、雷诺应力和脉动速度等湍流统计量的均方误差均可以控制在11%以内. 在DUGKS框架下, 与文献中利用自适应亚格子应力模型相比, 文章结合Musker壁面模型的处理方法, 可以得到更精确的流向速度和雷诺切应力.

     

    Abstract: The mesoscopic-scheme-based large eddy simulation (LES) has emerged as an alternative approach to study turbulent flows. The discrete unified gas kinetic scheme (DUGKS) is a relatively newly developed mesoscopic method, and the realization of LES in DUGKS is still in its early stages. In this paper, a DUGKS-LES algorithm is proposed by coupling the standard off-wall Smagorinsky subgrid model and the Musker wall model. Firstly, the relation between the effective total stress and the non-equilibrium distribution function for LES within the DUGKS framework is derived. When solving the wall shear stress using the wall function, a rapid Newton iteration method is designed to ensure the convergence, by incorporating the approximate solution of the inverse problem. Finally, large eddy simulations of the turbulent channel flows at friction Reynolds numbers of 180, 395 and 950 are performed to validate the proposed DUGKS-LES method. Compared with the results from the spectral method, the mean square errors of turbulence statistics such as streamwise velocity, Reynolds stress and fluctuating velocity are maintained below 11%. In the DUGKS framework, when compared with the wall-adapting subgrid models used in the literature, the proposed DUGKS-LES method incorporating the Musker wall model can achieve more precise results in terms of mean streamwise velocity and Reynolds shear stress.

     

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