ABSTRACT The Discrete Element Method (DEM) for modelling of flow over rough walls is revised in the framework of the DANS (Double Averaged Navier-Stokes) equations, with a special focus on the drag term appearing in the mean momentum equation as a key to the robustness of the model. A set of 14 Direct Numerical Simulations (DNS) of channel flows with systematically varying roughness topographies is considered to assess the performances of different drag coefficient closures. While the standard model of Taylor et al. [J. Fluids Eng. 107 (1985), 251–257] is found not to be successful in reproducing the distribution of the drag force, a new model is derived. The new model along with the model recently proposed by Kuwata et al. [Int. J. Heat Fluid Flow 77 (2019), 186–201] are employed for the solution of channel flow along with a simple mixing length model. Both models are shown to be successful in prediction of roughness function as long as a constant in the latter model is readjusted. The velocity profiles are also well recovered and in particular the roughness sublayers are accurately reproduced.

中文翻译：

---

双平均 Navier-Stokes 方程中阻力系数建模对预测粗糙度影响的重要性

摘要 用于模拟粗糙壁面流动的离散元方法 (DEM) 在 DANS（双平均纳维 - 斯托克斯）方程的框架内进行了修订，特别关注出现在平均动量方程中的阻力项，作为模型的稳健性。一组 14 个具有系统变化的粗糙度地形的通道流的直接数值模拟 (DNS) 被认为是评估不同阻力系数闭合的性能。而泰勒等人的标准模型。[J. 流体工程 107 (1985), 251–257] 被发现不能成功地再现阻力的分布，因此推导出一个新模型。新模型以及 Kuwata 等人最近提出的模型。[国际。J. 热流体流动 77 (2019)，186-201] 用于解决通道流动以及一个简单的混合长度模型。只要重新调整后一个模型中的常数，这两个模型都可以成功地预测粗糙度函数。速度剖面也得到了很好的恢复，特别是粗糙度子层被准确地再现。