波流作用的近岸圆柱局部床面侵蚀

波浪流对近岸浅水带床面作用强烈,该区域结构物局部床面侵蚀显著,潜存致灾威胁。用三维数值方法研究了瞬态孤立波作用下非黏性沙海床上的近岸圆柱体局部冲刷规律,分析了波浪流冲刷的3类主要影响要素,讨论了近岸地形条件影响下的波流冲刷深度。研究认为,表征浅水波流特征和柱体尺度的无量纲数Urp与KC数存在非独立关系,二者均能分别反映波流冲刷的主要规律;表示泥沙运动的力学参数Shields数在波流动床条件下仍对柱体局部冲刷有贡献;近岸地形通过床面坡度对波破碎的增强及堤岸挡墙对波浪的反射,都会影响到局部冲刷。

Solitary wave scour around a cylinder in shoaling conditions

Solitary wave attack causes substantial erosion and significant local scour around cylindrical structures in nearshore shallow water conditions. The transient wave scour around a coastal cylinder on noncohesive sediment seabed was investigated by three-dimensional numerical method. Three kinds of influential factors on wave flow scour were identified. In addition,the maximum scour depths in different coastal topography conditions were analyzed. The results show that either modified Ursell (U_rp) number or Keulegan-Carpenter (KC) number, representing the ratio of wave characteristic and cylinder scale, governs the maximum scour depth. Furthermore, the dependent relationship between these two numbers was also obtained. In live-bed conditions, the Shields parameter of sediment still contributes to the local scour of the cylinder. The offshore seabed slope and embankment wall have effects on wave breaking and wave reflection respectively,which therefore influence the scour depth.