浅化波浪层流边界层流速分布r特性的数值分析

摘要

An improved second-order numerical model for wave bottom boundary layer is developed,which includesboth effects of wave Reynolds stress and mean horizontal pressure gradient.The simulated instantaneous velocityprofiles,oscillatory velocity amplitudes and mean velocity profiles in the laminar boundary layer beneath shoalingwaves are in good agreements with the experimental data.Effects of various dynamic processes on the mean velocitydistribution are discussed.Results reveal that the mean velocity is directed onshore and offshore in the lower andupper regions of the bottom boundary layer,respectively,and this pattern becomes increasing obvious as waveshoals over a sloping bed.The near-bed onshore mean velocity is dominated by wave Reynolds stress related to thesecond-order advective terms,while the offshore mean velocity in the upper region is mostly due to the mean horizontalpressure gradient related to the undertow current.%建立了同时考虑波致雷诺应力和时均水平压强梯度影响的二阶波浪边界层数学模型,模型计算得到的浅化波浪层流边界层内瞬时流速剖面、振荡速度幅值和时均流速剖面均与水槽实验数据吻合较好,在此基础上探讨了浅化波浪边界层流速分布特性及其影响机制.随着波浪的浅化变形,边界层内时均流速剖面"底部向岸、上部离岸"的变化特征越来越明显.这是二阶对流项引起的波致雷诺应力和离岸回流引起的时均水平压强梯度共同作用的结果,在床面附近由波致雷诺应力占主导作用并趋于引起向岸流动,在上部区域由时均水平压强梯度占主导作用并趋于引起离岸流动.