Research On Coupling Model Of Hydrological And Hydraulics Based On Adaptive Grid

The flood disaster is one of the main natural disasters that endanger the economic development and population security.Affected by land features,climate and other conditions,China's flood disaster remains serious,flood control and disaster reduction has always been one of the main objectives of water conservancy work.Flood forecasting is an important reference for flood control decision making.How to accurately simulate flood inundation and propagation is an important subject for flood forecasting.Hydrological model and hydraulic model are the core components of flood forecasting system.In this study,distributed physic s-based hydrological model were carried out,making diffusion wave equation as core,to describe the water circulation movement of rainfall-infiltration and slope confluence.And based on the shallow water equation,a two-dimensional hydraulic model was carried out with numerical stability and accuracy.Based on the theory of characteristic wave propagation in the numerical calculation of hydraulic model,a new coupling method was established to realize the dynamic bidirectional coupling of hydraulic model and hydrological model.Different from the problems caused by the calculation of the two kind of models without interference and boundary fixation in the unidirectional coupling method,the dynamic bidirectional coupling method used the calculation of discharge in the coupling boundary as core target.The dynamic bidirectional coupling method follows the mass and momentum conservation theory,and can adjust the calculation model and the application area of different models according to the flow state change,so as to improve the prediction accuracy and calculation efficiency of the model.The outcome is better when flood simulation is carried out.In order to solve the problem that the computational scales of the two models may be inconsistent in the application of the coupled model,an adaptive quadtree grid generation algorithm was established,which had high computational efficiency and can be compatible with computing units of different scales to accurately describe the changes of terrain and flow field.In the process of grid generation,grid coding and grid size were used as retrieval conditions to realize global one-way retrieval and avoid repeated checking of grid.Numerical examples and physical experiments were used to verify the performance of the coupling model,and verify the stability and accuracy of the numerical scheme.By comparing the dynamic bidirectional coupling model with the unidirectional coupling model,the simulation results show ed that the dynamic bidirectional coupling method was closer to the real flow.The comparison between computation results of the coupling model based on quadtree mesh and orthogonal mesh verifi ed that the quality of adaptive mesh can guarantee the accuracy of calculation.The model was applied to the flood forecasting of Longxi river basin,and the designed rainfall flood with different frequencies were used to verify that the model can accurately simulate the evolution of rainfall flood in small river basin,providing reference for flood control work.