Kazemi Ehsan, Nichols Andrew, Tait Simon, Shao Songdong
Department of Civil and Structural Engineering The University of Sheffield Mappin Street Sheffield S1 3JD UK.
Int J Numer Methods Fluids. 2017 Jan 10;83(1):3-27. doi: 10.1002/fld.4248. Epub 2016 May 25.
A numerical model based on the smoothed particle hydrodynamics method is developed to simulate depth-limited turbulent open channel flows over hydraulically rough beds. The 2D Lagrangian form of the Navier-Stokes equations is solved, in which a drag-based formulation is used based on an effective roughness zone near the bed to account for the roughness effect of bed spheres and an improved sub-particle-scale model is applied to account for the effect of turbulence. The sub-particle-scale model is constructed based on the mixing-length assumption rather than the standard Smagorinsky approach to compute the eddy-viscosity. A robust in/out-flow boundary technique is also proposed to achieve stable uniform flow conditions at the inlet and outlet boundaries where the flow characteristics are unknown. The model is applied to simulate uniform open channel flows over a rough bed composed of regular spheres and validated by experimental velocity data. To investigate the influence of the bed roughness on different flow conditions, data from 12 experimental tests with different bed slopes and uniform water depths are simulated, and a good agreement has been observed between the model and experimental results of the streamwise velocity and turbulent shear stress. This shows that both the roughness effect and flow turbulence should be addressed in order to simulate the correct mechanisms of turbulent flow over a rough bed boundary and that the presented smoothed particle hydrodynamics model accomplishes this successfully.
基于光滑粒子流体动力学方法开发了一个数值模型，用于模拟水力粗糙床面上深度受限的湍流明渠水流。求解了二维拉格朗日形式的纳维-斯托克斯方程，其中基于床面附近的有效粗糙度区域采用基于阻力的公式来考虑床面球体的粗糙度影响，并应用改进的亚粒子尺度模型来考虑湍流的影响。亚粒子尺度模型基于混合长度假设构建，而非标准的斯马戈林斯基方法来计算涡粘性。还提出了一种稳健的入流/出流边界技术，以在流动特性未知的入口和出口边界处实现稳定的均匀流动条件。该模型用于模拟由规则球体组成的粗糙床面上的均匀明渠水流，并通过实验速度数据进行验证。为了研究床面粗糙度对不同流动条件的影响，模拟了12个不同床面坡度和均匀水深的实验测试数据，模型与流向速度和湍流切应力的实验结果之间观察到了良好的一致性。这表明，为了模拟粗糙床面边界上湍流的正确机制，粗糙度效应和流动湍流都应予以考虑，并且所提出的光滑粒子流体动力学模型成功地做到了这一点。
