考虑渗流效应的冲流带泥沙起动机理研究

Study on the sediment initiation considering the seepage in the swash zone

为揭示内部渗流对海岸冲流带泥沙起动的影响,系统地开展了斜坡海床冲流特性与泥沙起动机理研究。通过室内水槽开展了孤立波在可渗透和不可渗透斜坡海床上的冲流试验,测试了冲流过程中波高、波速等变化规律;建立了渗透海床冲流数值模型并通过试验结果进行验证;深入分析了床面渗流对其波浪流场动态特征以及床面泥沙起动的影响机理。研究表明,床面渗流作用加剧波浪的不对称性,在波浪上冲过程中因床面强入渗作用而增大了床面切应力;回流过程因入渗所造成流量损失而导致床面切应力减小。床面渗流引起床面颗粒有效重度和切应力变化而导致泥沙希尔兹数大大增加,加剧了泥沙起动现象,且床面切应力改变是引起泥沙希尔兹数变化的主要因素。

In order to reveal the effects of seepage on the sediment initiation in swash zone,the experimental and numerical studies were performed in this paper.Firstly,the experiments of solitary wave run-up over permeable and impermeable slope was carried out in an indoor flume,the wave height and flow velocity were measured.Secondly,corresponding numerical simulations were performed and validated by the flume test results.Finally,the influence of seepage on the hydrodynamics in the swash zone and sediment initiation were assessed.The test results show that the asymmetry of wave becomes obvious under the effect of seepage.Strong infiltration during uprush increases the shear stress on the seabed surface,and wave downrush leads to the reduction of seabed shear stress due to the flow loss.It is also found that the seepage changes the effective weight as well as the shear stress of seabed soil particles,which leads to the variations of Shields parameter and greatly increase instability of sediment particles.The change of shear stress over permeable slope is the main reason for the Shields parameter variation of seabed particles.This study can provide guidance for the assessment and treatment of sediment transport in the swash zone.