近岸波生流运动三维数值模拟及验证

3D numerical modeling of nearshore wave-induced currents

  • 摘要: 开发建立了近岸波生流运动三维数值计算模式。模式中,引入了三维时均剩余动量、破波表面水滚、波浪水平与垂向紊动作为主要驱动力,同时考虑了波流共同作用的底部剪切力。推导了可综合反映底坡、能量传递率和密度影响的水滚能量传输方程;将Larson-Kraus的二维波浪水平紊动系数表达式拓展至三维。采用大量实测数据和文献资料测试验证了所建模式,表明所建模式可有效模拟波浪增减水、底部离岸流、沿岸流、裂流、堤后环流等不同维度的波生流现象。此外,研究也表明破波水滚效应可解释波生流峰值向岸推移的物理现象,从而在模拟中不能忽略;破波带内沿岸流速垂向较为均匀的现象与波浪附加垂向紊动有关。

     

    Abstract: A threedimensional (3D) numerical model for nearshore waveinduced currents is established,in which the phaseaveraged 3D residual momentum flux,surface roller and wave turbulence are introduced as driving forces,and the wavecurrent combined bottom shear stress is taken into account.An energy balance equation of the surface roller is derived,considering the bottom slope,energy transmission rate and roller density.The LarsonKraus formula for the 2D wave turbulent mixing coefficient is extended to its 3D form.A number of experimental cases are used to validate the model,including the wave setup/setdown (1D),undertow (2-DV),longshore current (Q3-D),rip current (2-DH) and the circulation behind a detached breakwater (2-DH).The validation results show that the model is able to effectively describe the waveinduced current phenomena of various dimensions,and the incorporation of the surface roller is mandatory.The uniformity of the longshore current speed profile in the surfzone is related to the vertical turbulent mixing in the effect of waves.

     

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