磨刀门水道枯季底边界层的泥沙交换过程

河口底边界层细颗粒泥沙运动往往受边界层内多种尺度的动力过程影响而变得十分复杂。由此,基于座底支架上的ADV与OBS,于2010年枯季在珠江磨刀门水道分别进行大、中、小潮的底边界层观测,对磨刀门水道底边界层湍流动力特征与小尺度泥沙交换过程进行研究。结果表明:悬沙有效沉速、床面切应力与底床侵蚀率的变化范围随着潮差的增大而增大;底床侵蚀率与平均流速变化规律相似,当流速小于0.3 m/s时,侵蚀率基本保持在0.002 kg/m2左右,流速超过此临界值时,床面泥沙发生再悬浮。悬沙和床沙交换过程随着潮差增大而增强,且落潮时段强于涨潮时段。

Sediment Exchange Process within the Bottom Boundary Layer at Modaomen Channel

The movement of grain sediment within the bottom boundary layer is influenced by complicated, multi-scale dynamic processes. Dynamic characteristics of turbulence and small-scale sediment exchange process within the bottom boundary layer at modaomen channel are discussed based on bottom boundary layer observation data over various tide levels by using ADV and OBS in winter of 2010. The result shows that: ① The ranges of sediment settling velocity, bottom stress and bed erodibility increase with tidal range.②Bed erodibility changes are similar to mean velocity. When velocity is less than 0.3m/s, the bed erodibility remains at about 0.002 kg/m². If velocity is larger than 0.3 m/s, sediment will resuspend. ③ Suspended sediment and bed sediment exchange process is enhanced with increasing tidal range, and it is stronger during ebb tide than during flood tide.