桥墩概化方法对水动力数学模型计算结果的影响研究

The Influence of Pier Generalization Methods on the Simulation Results of Hydrodynamic Numerical Model

为分析平面二维数学模型中不同桥墩概化方法对防洪评价结果的影响,借助于MIKE 21水动力模型,以长江宜昌江段某桥梁工程为例,分三种不同的桥墩概化方法计算了桥墩对百年一遇洪水位、行洪流速的影响。结果表明:三种概化方法反映出来的影响规律基本一致,桥墩上游水位增加、流速减小;桥墩所在断面水位增加,流速增加;桥墩挡水面以下河段流速减小,挡水面以外河道两侧行洪流量增加,流速增加。但采用网格地形高程修正法得出的计算结果更为合理,考虑到数学模型计算稳定性需要,推荐使用网格地形修正和糙率修正相结合的方法。

In order to identify the effects of different pier generalization methods used in two-dimensional math-ematical model for flood control evaluation, three simplified methods of pier have been studied with the help of the MIKE 21 software and for the Yichang Yangtze River Bridge project under the hydrological conditions of 100-year flood. The simulation results showed nearly the same influence laws for the different pier methods. The water level increased while the velocity declined on the upstream. In contrast, both the water level and velocity at pier section increased simultaneously. The flow velocity decreased at the water blocking part downstream, while the flow velocity and the flow rate increased at unblocking parts on both sides of the river downstream. Neverthe-less, the simulation results of mesh elevation correction method seems more reasonable, and taking into account of the model computational stability, the combination of mesh elevation correction and roughness correction is recommended in practice.