Baykal C, Sumer B M, Fuhrman D R, Jacobsen N G, Fredsøe J
Technical University of Denmark, Department of Mechanical Engineering, Nils Koppels Alle 403, Kongens Lyngby 2800, Denmark
Technical University of Denmark, Department of Mechanical Engineering, Nils Koppels Alle 403, Kongens Lyngby 2800, Denmark.
Philos Trans A Math Phys Eng Sci. 2015 Jan 28;373(2033). doi: 10.1098/rsta.2014.0104.
Flow and scour around a vertical cylinder exposed to current are investigated by using a three-dimensional numerical model based on incompressible Reynolds-averaged Navier-Stokes equations. The model incorporates (i) k-ω turbulence closure, (ii) vortex-shedding processes, (iii) sediment transport (both bed and suspended load), as well as (iv) bed morphology. The influence of vortex shedding and suspended load on the scour are specifically investigated. For the selected geometry and flow conditions, it is found that the equilibrium scour depth is decreased by 50% when the suspended sediment transport is not accounted for. Alternatively, the effects of vortex shedding are found to be limited to the very early stage of the scour process. Flow features such as the horseshoe vortex, as well as lee-wake vortices, including their vertical frequency variation, are discussed. Large-scale counter-rotating streamwise phase-averaged vortices in the lee wake are likewise demonstrated via numerical flow visualization. These features are linked to scour around a vertical pile in a steady current.
利用基于不可压缩雷诺平均纳维-斯托克斯方程的三维数值模型，对垂直圆柱体在水流作用下的水流和冲刷情况进行了研究。该模型包含：（i）k-ω湍流闭合；（ii）涡旋脱落过程；（iii）泥沙输运（包括床沙和悬沙），以及（iv）河床形态。特别研究了涡旋脱落和悬沙对冲刷的影响。对于选定的几何形状和水流条件，发现不考虑悬沙输运时，平衡冲刷深度会降低50%。另外，发现涡旋脱落的影响仅限于冲刷过程的非常早期阶段。讨论了马蹄涡以及背风波涡等水流特征，包括它们的垂直频率变化。通过数值流动可视化同样展示了背风波中大规模反向旋转的流向相位平均涡旋。这些特征与稳定水流中垂直桩周围的冲刷相关。
