The Flowing Water Scheme Optimization Research Of River Network In Jiaxing City District

In order to improve water environment,Jiaxing city is relying on the construction of sponge city,with the help of engineering measures of "water diversion and sewage dilution" to strengthen river self-purification ability and speed up governance of the black smelly channel.The use of the existing engineering facilities to improve the urban river water dynamic conditions and optimize plans of water diversion and water draining,has the vital significance for production practice.The Saint-Venant equations are used to establish unsteady flow mathematical model in this paper,using Preissmann weighted implicit scheme at four o'clock,discrete equations of space and time,with double relaxation iteration method to solve the unsteady flow.This model in the paper is verified by two computational examples.One is loop river network Sen and Garg put forward,the other is topology river network Islam put forward.In loop river network calculation,discharge hydrograph in the cross sections this paper calculated approximately agree with Sen and Garg's.The maximum relative error of the peak of discharge hydrograph in the cross sections this paper calculated and the peak provided by the literature reach to-2.67%.In the topology river network calculation,discharge hydrograph and stage hydrograph in the node 11 and node 12 this paper calculated approximately agree with Islam's.The maximum relative error of the peak of discharge hydrograph this paper calculated and the peak provided by the literature reach to 1.17%.The maximum absolute error of the peak of stage hydrograph and the peak provided by the literature reach to-0.02m.This shows that mathematical model of jiaxing city have the capacity to motion simulation of complex river network open channel flow.The observation of the water level value of the 12 typical cross sections in the river network of jiaxing city based on two water diversion and water draining schemes were obtained.The roughness of river channel in jiaxing city was calibrated by using the prototype observation data.Roughness is in line with the rate fixed for each channel morphology,revetment material,roughness.The absolute error of the water level calculatied by the calibrated model and the actual water level in typical cross sections is within±0.05m.That Shows that the established model is suitable for the selected area and has higher precision.Based on the above calibrated unsteady flow mathematical model of the Jiaxing city,A total of 57 kinds of schemes under three conditions:low water level,normal water level,high water level are numerically simulated.With average flow velocity in river network,the rate of stagnant water,flows into the south lake flow,verage flow velocity in key rivers as optimal index,The external schemes,internal and external combination schemes,plan schemes under three conditions are analyzed.And the pump station row of fresh water and their optimized schemes are respectively obtained.