| Global climate change leads to the frequent occurrence of extreme weather,which leads to serious floods disaster.The hydrodynamic model can effectively simulate and predict the degree of flood disaster,and can provide scientific data support for flood risk assessment and flood disaster early warning.In this work,aiming at the problem that the treatment of the river engineering buildings is not perfect in the simulation area of two-dimensional hydrodynamic model,based on GAST(GPU Accelerated Surface Water Flow and Transport)model developed by xi'an university of technology,applying source term method based on water conservation achieves the current simulation of river engineering buildings(e.g.Weir,gate and dam-break)in two-dimensional hydrodynamic model.The implementation steps of the source term method are as follows:(1)In the simulation area,the upstream and downstream grids of the river structures are specially marked to stop the calculation of flux by the Riemann solver;(2)The head information of the upstream marked grid is used as the input condition of the corresponding flow calculation formula to calculate the discharge(the discharge through the weir is calculated by the weir flow formula,and the discharge out of the gate is calculated by the orifice flow formula,the dam break of gradually collapses adopts the DB-IWHR dam break model considering the lateral expansion and vertical scour of the breach to calculate the breach discharge);(3)Convert the calculated discharge to the change value of the grid water level,subtract the change value from the water level of upstream marked grid,and add the change value to the water level of downstream marked grid.The applicability and accuracy of the 2-D hydrodynamic model using the source term method to treat the broad crested weir and flat bottom gate are verified by an ideal example and an actual example of the overflow flow in the spillway of a reservoir.When the ideal example is used for verification,the numerical simulation results of broad crested weir and flat bottom gate are in good agreement with the calculated results of corresponding formula.When the spillway of Ganyu reservoir is used to verify the broad crested weir,the simulated curve of water level and discharge results is closer to the measured values.By coupling the breach evolution model DB-IWHR,a high-performance coupling model including the two-dimensional hydrodynamic process in the upstream reservoir area,the evolution of the breach and the two-dimensional flood propagation in the downstream inundation area is established.The model has the following advantages:(1)the source term method is simple and easy to implement,and has good grid adaptability,and does not need special treatment HLLC Riemann solver which is calculated the grid flux;(2)the calculation of the discharge of the breach considers the lateral extension and vertical erosion process;(3)the two-dimensional hydrodynamic method is used to simulate the flood evolution process of the upstream and downstream areas of the breach,and GPU acceleration technology is introduced improve simulation efficiency.The model is applied to simulate the dam break process of Tous in Spain.Compared with Mike21 FM model,in terms of simulation accuracy,the RMSE of simulation results is 0.4045 and 0.9653 respectively.The results of coupling model simulation are closer to the measured values.In terms of simulation efficiency,GPU acceleration technology is used in the coupling model and Mike21 FM model,and the hardware used is NVIDIARTX 2080 graphics card.The simulation time of the coupling model is 3722s,that of the Mike21 FM model is 63450s,and the calculation efficiency of the coupling model is 17.04 times that of the Mike21 FM model.In the process of dam break simulation of Tangjiashan barrier lake and Baige barrier lake on Jinsha River,a river restructuring method is proposed for flood propagation simulation in mountainous areas without high-precision topographic data.According to the satellite image map of the same period,the plane contour of the river channel is mapped out in DEM;secondly,the maximum normal water depth of the river channel is calculated by manning formula,and the maximum normal water depth is used as the depth of excavation to restructure the underwater topography of river channel.When the restructured channel topography is used for flood propagation simulation,the simulation results of Tangjiashan barrier lake dam break are in good agreement with the measured values.The discharge process of Baige barrier lake dam break simulation of Jinsha River is obviously delayed at yebatan.The main reason is that the accuracy of the terrain data used in the model is low,and the description of the main channel topography is very terrible compared with the actual river channel,especially underwater topography.Through comparative analysis of the influence of terrain restruction on flood propagation,the phenomenon of delay of flood arrival time and attenuation of flood peak flow is more serious in the non restructured terrain,which is mainly because the non restructured terrain fails to reflect the real terrain of the river,especially the main channel,which is wide and shallow,and deviates from the actual narrow and deep river,which leads to flood propagation in the floodplain,the contact area between the simulated flow and the terrain increases,and the simulated water depth is shallow,so the friction is large,the energy loss is increased,the discharge is reduced,and the arrival time of flood is delayed.It can be seen that the restructured terrain is closer to the actual terrain,and the impact on flood propagation is relatively small,and the simulation results are more reasonable. |
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