岛屿地貌单元的湍流能耗物理模型试验

岛屿地貌单元是珠江三角洲发育演变过程中的沉积核心,研究其消能机制,对理解河口动力过程及三角洲发育演变有重要意义。通过建立岛屿地貌单元的湍流能耗特性概化物理模型,基于16 MHz ADV采集高频流速数据,统计了时均及湍流特征量,并利用惯性耗散法分析了岛屿地貌单元的湍流动能耗率。结果表明,相同控制条件下岛屿地貌单元的形态阻力致使尾流中紊动强度量值为明渠的2~3倍,湍流剪切应力及湍流动能较明渠水流的大近1个数量级,湍流动能耗散率比明渠水流湍流动能耗散率大1~2个数量级。岛屿地貌单元的局部形态阻力导致尾流时均流速的空间梯度、切应力增大是湍流能耗率增大的原因。岛屿地貌单元的汇流作用增加了下游尾流区的水流掺混,并在尾流区域形成大量微尺度涡,导致区域湍流能耗作用增强,有利于岛屿沉积核心发育。研究成果有助于理解河口动力及三角洲的发育演变过程。

Physical Model Experiment on the Turbulent Kinetic Energy Dissipation Induced by the Island Topography

Island topography is the core of the evolution of the Pearl River Delta, and is the typical high energy consumption zone at Pearl River Estuary. Research on the turbulent kinetic energy dissipation induced by the island topography unit is important to the explanation of the Pearl River Estuary dynamic phenomenon and understanding of dynamic estuarine processes. The high frequency velocity was collected by SonTek 16MHz ADV. Turbulent energy dissipation induced by island topography was studied with a physical model, and high frequency velocity was collected for the analysis of the time averaged velocity and turbulent variable. Turbulent energy dissipation was calculated by inertial dissipation method for wake flow induced by the island topography. Model test conditions in the islands landform unit form drag due to wake turbulence intensity value is 2 times to 3 times than the channel flow, turbulent shear and turbulent kinetic energy should be nearly ten times than that of the open channel flow. From the local turbulent equilibrium and energy transfer theory, the higher spatial gradients of velocity, turbulent stress and more smaller scale eddies produced by the island topography is the important reasons that make the turbulent energy dissipation rate increased 1-2 order of magnitude.