可渗透海床单桩孤立波破碎波浪力数值研究

Numerical investigation of breaking solitary wave force on vertical monopile on porous seabed

当波浪传播至近岸浅水区时易发生破碎,波浪破碎后水体直接拍击单桩结构,其波浪作用力显著增大,可能导致结构失稳破坏。首先建立包括斜坡海床的数值波浪水槽,并与已有研究进行对比验证。进而开展考虑斜坡海床可渗透性的孤立波数值模拟,分析孤立波传播与浅水化破碎特征,着重研究竖直单桩上破碎波浪力的特性,及其与单桩位置、海床渗透率的关联性。数值研究发现:对于低渗透率海床,随着单桩位置由深水向岸线位置变动,其所受波浪力先增后减,所受波浪力最大的桩体位置随海床渗透率增加而从波浪破碎点前方移动至破碎点后1D处,而在高渗透率海床上不同位置处桩体所受波浪力均较小;随海床渗透率等梯度增加,海床消波作用逐渐增强,波浪破碎进程延缓,波浪破碎点向岸线方向加速移动,单桩上破碎波浪力呈整体下降趋势,但可能因波浪破碎点的位置变动导致部分位置桩体所受波浪力异常增大。

Waves propagating to the shallow-water zone are more likely to break. When breaking waves attack monopile directly, the breaking wave force will remarkably increase and result in the instability and failure of coastal structures. Firstly, we the numerical model was set up including a submarine slope and the model was validated with existing studies. Then numerical simulations were carried out about the solitary wave, taking the slope’s permeability into account. The characteristics of the solitary wave’s propagation and breaking in the shallow-water zone were analyzed. The characteristics of the breaking wave force acting on the vertical monopile and the correlation between the breaking wave force and pile positions or seabed permeability were focused on. Numerical results show that the breaking wave force acting on the monopile increases at first and then decreases with the monopile moving from the deep-water zone to the coastal line on the low permeability seabed. The positions where the monopile suffers maximum wave force transfer from the breaking point to the position 1 D behind the breaking point. But on the high permeability seabed, the breaking wave force is always small. When the seabed permeability increases with a constant gradient, the wave damping effect is enhanced and the wave breaking process is delayed. The breaking point moves towards the coastal line more quickly. Breaking wave force also presents an overall downward trend. But there can be abnormal great breaking wave force at some positions because of the changed breaking points.