湄洲湾潮流和污染物输运的高精度非结构网格模拟

针对湄洲湾不规整岸边界和复杂的潮流变化等特征,模型采用高精度的二维非结构网格浅水流模型对湾内潮流水动力进行模拟。基本方程离散和有限体积法思想,并利用改进的QUICK格式提高对流项计算精度,在扩散通量估算上引入具有良好数值性能的超松弛校正方法。不合理的压力波由Rhie-Chow的动量插值方法加以抑制,水位校正方程结合SIMPLEC程式导出。通过对湄洲湾小潮的水动力模拟,结果表明,潮位、流速、流向的实测值和计算值吻合良好。另外,模型还对海湾内肖厝峰尾和鲤鱼尾两处主要污水排放口的COD排放进行了计算,模拟结果较好地反应了湄洲湾内污染物输运特征,为更好地进行近海水污染控制提供有力的手段。

High Order Numerical Simulation of Tidal Flow and Pollutant Transport in Meizhou Bay Based on Unstructured Grids

According to characteristics of Meizhou Bay,such as irregular boundaries and complicated variations of tidal flow,a new high-order numerical model based on 2D unstructured grid is proposed for basic shallow hydraulic equations.The discretization is based on Finite Volume Method(FVM).In order to improve the numerical precision,a modified QUICK is adopted to calculate convective flux.Additionally,over-relaxation is used to estimate diffusion flux in view of its good numerical stability and precision.The pressure oscillation is suppressed by using Rhie-Chow's momentum interpolation method to derive water level correction equation based on SIMPLEC procedure.Spring tide and neap tide in Meizhou Bay are both simulated for the validation of the model.The observed tide level,magnitude of velocities and their corresponding directions are in good agreement with the computational results.By use of the reliable velocity fields predicted,two important pollutant discharging outfalls were considered to simulate the concentration fields of COD and its transport characteristics were better represented by the predicted results.So the model could provide an effective method to simulate tidal flow and pollutant transportation,as a good way to control pollutant discharge at the bay or shore.