局部冲刷坑发展过程的泥沙输运特性

为揭示水流作用下沙质河床结构物周围床面冲刷过程中的泥沙输运特性,采用三维紊流、考虑推移质和悬移质运动的河床变形数值模拟,研究了清水冲刷和动床冲刷条件下,墩柱型结构物局部冲刷过程中悬移质和推移质泥沙输运贡献及其与马蹄涡流特征量、床面切应力以及泥沙悬浮指数的相关性。研究发现,清水冲刷条件下,悬移质输运占比较小,推移质泥沙输运占优;动床冲刷条件下,悬移质输运的贡献随悬浮指数的减小迅速增大;冲刷过程中悬移质和推移质输沙率与床面切应力变化趋势一致,结构物周围局部切应力的大小与马蹄涡涡量呈正相关关系。

Study on the mechanism of water-sediment interaction in the scouring process around a pile

Aimed at exploration of the sediment transport behavior in local scouring process around a struc-ture,3D turbulent flow equations coupled with bedload and suspended load transport,as well as bed defor-mation were used to numerically simulate the local scour and investigate the contribution of the two kinds of sediment transportation, horse-shoe vortex, and the correlation of suspended load with the sediment sus-pension index under clear water and livebed conditions. It was found that under the clear water scour condi-tion, the transport of suspended load contributes a relatively small proportion, and the scouring process is dominated by bed load transport which contributes approximately up 95 percent. Under the live bed scour condition, suspended load transport increases rapidly with the decrease of the particle suspension index. In the scouring process, the variation of sediment transport rate for suspended load and bed load is consistent with the trend of the local shear stress around the structure. Further, the variation of the bed shear stress is positively controlled by the horseshoe vortex.