雖然風浪數值模式目前已被廣泛的使用，但此種模式之架構是相位平均模式，無法描述波浪折、繞射共存效應。為了要彌補模式的缺失，本文以 Hsu 等人 (2005) 提出之 WWM ( wind wave model ) 風浪模式為基礎，參考 Holthuijsen 等人 (2003) 所提出的相位非耦合模式 ( phase-decoupled model )，並從演進型緩坡方程式 ( evolution equation of mild slope Equation，EEMSE ) 中考慮海床坡度、海床曲率和浪流交互作用之影響，經由交互疊代方式在 WWM 模式中考慮波浪折、繞射共存的影響機制。本文先從波浪交互作用之緩坡方程式推導繞射修正參數，再以相位非偶合模式修正波浪傳遞方向之變化率，重新代回波浪作用力平衡方程式 ( wave action balance equation ) 計算方向波譜。本文同時以五種不同案例來進行模式驗證，並探討繞射修正參數每一個增加項對於計算結果的影響性，以便分析模式計算波浪繞射之合理性。數值計算結果顯示，理論值和觀測值呈現良好一致性。

The WWM (wind wave model) is extended to account for wave refraction–diffraction for wind waves propagating over a rapidly varying seabed in the presence of current. The wave diffraction effect is introduced into the wave action balance equation through the correction of wavenumber and propagation velocities using a diffraction-corrected parameter. The approximation is based on the mild-slope equation for wave refraction-diffraction with current effect on a rapidly varying sea bottom. The relative importance of additional terms that influence the diffraction corrected parameter in the presence of currents was first discussed. The comparison of numerical results with other numerical models and experiments show that the validity of the model for describing wave propagating over a rapidly varying bottom with current effect is satisfactory. The implementation of this phase-decoupled refraction diffraction approximation in WWM shows capability of the present model can be used in most practical engineering situations.

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