摘要
在台风等极端天气状况下,强烈的波致底流速和潮流的共同作用使海底沉积泥沙冲刷严重。采用数值试验的方法,探讨了台风作用下受海底自由沉物的影响造成的沉积泥沙被加速冲刷的过程。数值计算工具采用了SWAN海浪模式和DRAMBUIE冲刷模式。结果显示:波致底流速随水深的增加而减小,但在高风速作用下,最大底流速并不发生在水深最小处;在相同水深条件下,背景风速作用下波致底流速与台风作用下的底流速之间存在数量级的差别。自由沉物周围的冲刷坑在无回填发生时,其深度随时间持续增加,增加的幅度与底流速的变化幅度一致;冲刷坑最终深度与底流速具有正相关关系。底质粒径对冲刷坑最终深度有显著影响;粗、细颗粒底质会随底流速增加而出现易冲刷性改变的现象,以某流速为界,小于该值细颗粒底质易被冲刷,大于该值则粗颗粒易被冲刷。
Under extreme weather conditions such as typhoons,sediment will be eroded very severely in the shallow shelf sea,under the coupled actions of strong near-bottom wave-induced orbit velocity and tidal current.The accelerated scouring process surrounding cylinder objects,on the effect of typhoon,has been evaluated based on numerical models.Firstly,the SWAN wave model was used to simulate the near-bottom waveinduced orbit velocity on the effect of typhoon.Then the DRAMBUIE model was used to simulate the process of the scour surrounding cylinder object under the different wave actions.The results show that near-bottom wave-induced orbit velocities are smaller,when the water depths are deeper.However,the near-bottom waveinduced orbit velocity was not the largest in the smallest water depth,because of the dissipation of energy induced by wave breaking and bottom friction in the shallow water.There is a magnitude difference of velocities between near-bottom orbit velocity on the effect of 10 m/s wind and that on the effect of typhoon.The depth of scour pit surrounding the cylinder object freely settling on seabed was continuously increasing with time when no infill happened.There was a positive correlation between the final depth of scour pit and the near-bottom current velocity.The scour depth induced by typhoon was obviously larger than that on the effect of normal wind at the same water depth.The depth of scour pit varied with the median grain size of surficial sediment in the same flow dynamic condition.
出处
《泥沙研究》
CSCD
北大核心
2014年第3期20-27,共8页
Journal of Sediment Research
基金
国家重大科学研究计划课题(2012CB956004)资助
关键词
台风
底流速
海底冲刷
自由沉物
数值模拟
typhoon
orbit velocity
seabed scour
cylinder object
numerical study
