Study on Numerical Models of Nearshore Currents Including Wave Nonlinearity or Wave Irregularity

本文的研究结论如下：（1）从数学上证明了现有的椭圆余弦波理论之间的相互关系是：Chappelear理论包括了其他理论。(2)利用斯托克斯波和椭圆余弦波的高阶解分析了海流-水深变化引起的波浪浅水和折射。(3)建立了波浪变形和近岸流的两种模型，并分别用斯托克斯波和椭圆余弦波理论估算了波浪特性。(4)在非线性长波方程特征解的基础上，建立了一维和二维波浪变形模型。这些模型也适用于不规则波的变形计算。(5)本文根据波浪作用谱密度守恒原理，建立了时变水流和水深引起的不规则波折射计算模型。数值计算表明，电流的时间依赖性会导致反向电流对方向谱的放大作用减弱。(6)建立了不规则波作用下的近岸流场模型，采用近似方法计算了绕射和反射对近岸流场的影响。该模型合理地解释了波浪变形的实验数据和与其结构形态相适应的电流斑图的形成。

The conclusions of this study are as follows ;(1) Mathematical proof is given that the interrelation among the existing cnoidal wave theories is such that the Chapppelear theory includes the other theories.(2) Wave shoaling and refraction due to current-depth variations are analyzed with use of higher order solutions of Stokes and cnoidal waves.(3) Two models of wave transformation and nearshore currents in which wave characteristics are estimated with Stokes or cnoidal wave theory are established.(4) One-dimensional and two-dimensional models of wave transformation are developed on the basis of characteristics solution for nonlinear long wave equations. These models are also applicable to the computation of transformation of irregular waves.(5) A model for refraction computation of irregular waves due to time-varying currents and water depth is established on the basis of conservation of wave action spectral density. Numerical computation shows that time-dependency of currents gives rise to reduction in the amplification effect of directional spectrum due to opposing currents.(6) A model of nearshore currents induced by irregular waves in the presence of coastal structures is completed, in which the effect of diffraction and reflection are evaluated with approximate ways. The model reasonably explains the experimental data of wave transformation and the formation of curent patterns appropriate to their configuration of structures.