模型以经Ｓｉｇｍａ坐标变换后具有自由表面的三维非线性Ｎａｖｉｅｒ－Ｓｔｏｋｅｓ方程为基本方程，以分裂算子法剖分动量方程，用全隐差分格式求解连续方程得到自由表面，最后计算完整的速度场．此外，采用紊流封闭模型求解垂直方向紊动粘滞系数，准确获得了摩擦影响层的潮流结构．应用本模型计算了北部湾的潮波运动，重现了Ｋ１、Ｍ２分潮潮波系统并揭示了潮流的空间结构特征 In the model, the three-dimensional nonlinear Navier-Stokes equation with free surface transformed by Sigma coordinate is taken as the basic equation, the momentum equation is split by split operator method, the free surface is obtained by solving the continuous equation by implicit difference scheme, and finally the complete velocity field . In addition, the turbulent closed model was used to solve the turbulent viscosity in the vertical direction, and the power flow structure of the friction-influencing layer was accurately obtained. Applying this model, the tidal wave motion of Beibu Gulf is calculated, and the tidal wave systems of K1 and M2 are reproduced and the spatial structure of tidal current is revealed