Analysis of influence of mesh partition on Mike21 calculation in flood impact assessment

Abstract

In order to study the impact of different grid mesh sizes on the calculation results of the model in the analysis of flood impact assessment, this paper takes the newly constructed bridge between the Niushou and Xiangyang sections of the Hanjiang River as an example. It simulates the influences of bridge construction on river flow under the six schemes of setting the bridge pier as a solid boundary, no internal mesh generation, and not participating in numerical calculation, and dividing the bridge pier local mesh size into 2m, 4m, 6m, 8m, and 10m. The results show that different grid sizes in the project have an effect on the river water level and the range of water level changes. The smaller the local grid size of the project relative to the building size, the greater the maximum water level change value, and the closer it is to the calculated value of the bridge pier as a solid boundary. By adding piers module of the model to generalize the project, the water level change in the model results is significantly smaller. Under the same water level change conditions, the larger the mesh size, the greater the scope of the project. For projects located in important river sections with significant water blocking effects, it is recommended that buildings be used as solid boundaries without participating in generating meshes or modifying local terrain to simulate the effects of water flow. The results are more in line with actual conditions.