Prediction-Correction Solution And Modeling Technology Research For One-Dimensional River Network Hydrodynamic Model

One-dimensional river network hydrodynamic model has be widely used today.It's accuracy can meet the pactical engineering requirements such as flood forecasting,water quality monitoring,channel improvement,but the calculation efficiency still needs to be further improved in terms of reservoir real-time scheduling.Therefore,based on the idea of prediction-correction,the paper bulids a high-efficiency model without any iteration by use linearization to elimianates the nonlinear characteristics of the control equations.The model takes Jing Jiang river and Dongting lake as the study area to verify its performance.The paper also researches how to select suitable grid size in the process of hydrodynamic modeling of one-dimensional river network.The innovative work and relevant achievement of this paper are summarized as follows:(1)Aiming at the iterative problem of solving the one-dimensional river network model,the model constructed in this paper based on the idea of prediction-correction,on the one hand,uses the Euler-Lagrangian method,local linearization,and semi-implicit method to eliminates the nonlinear characteristics of control equation during the discrete process of the control equation,on the other hand,uses the idea of domain decomposition to decompose the river network system into several subsystems.These measures enable the model only needs two step of prediction and correction to solve the velocity-pressure coupling problem,without iteration.(2)The paper uses the surveyed topographic data in 2003 and the surveyed hydrological data in 2005 to construct the Jingnan river network model.Defining three accuracy indicators to compare the calculated value with the measured value.The comparison results show that the calculated value of the model is close to the measured value.In order to verify the efficient calculation of the model,the paper compares the model with the HEC-RAS model.The results show that under the same calculation conditions,the calculation accuracy of this model is equivalent of the HEC-RAS model.The calculation efficiency is about 15% higher than that of HEC-RAS under single-core operation,and the efficiency advantage of this model is more obvious if the model uses multi-core to calculate.(3)The paper uses the surveyed topographic data in 2003 and the surveyed hydrological data in 2005 to construct the Jingjiang-Dongting Lake model.It verifies the calculation accuracy of the model for the complex river-lake system.The modified Morris screening method is used to analyze the sensitivity of the model parameters.The results show that the model is not sensitive to the time step,and the model calculation is stable under large time steps.Aiming at the problem that the one-dimensional hydrodynamic model is difficult to simulate floodplain,the paper proposes a virtual section method to correct the calculation result.It effectively improves the calculation accuracy of the model.(4)Aiming at the problem that the grid size is mostly selected by manual experience in the modeling process of one-dimensional river network model,this paper analyzes the influence of grid size changes on the calculation accuracy and efficiency by constructing 5different s Jingjiang-Dongting Lake river network models in grid size.Proposing a solution to get the optimal size of the grid which is defines an overall evaluation index for model accuracy and fit the relationship curve between this index and grid size to obtain the maximum grid size that meets the accuracy requirements.It can provide suggestion for build one-dimensional river network model.