Research On The Improvement Of Flow Properties Located On The Downstream Of Chan River And The Junction Of Chan River And Ba River

With the rapid speed of the process of urbanization along the river sides, point source and non-point source pollution has been increasing day by day, too. River ecosystem deteriorates,and the water environment pollution becomes a huge problem to be solved. Due to the small velocity of urban flow, the ability of river turbulent mixing is too weak and the quantity of air entrainment is reduced, so the self-purification ability of the river flow has weakened badly. To solve the issue of the black and stink river and the water retention, in this paper, the downstream of Chan river and the junction of Chan river and Ba river were taken as examples to analyze the factors affect the black and stink of the river by numerical simulation, aiming at researching the reason and affect factor of black and stink river, and present a solution to improve the water quantity of the study area.In this research, the DHI MIKE hydrodynamic model was applied,based on different characteristics of the domain, MIKE 11 Hydrodynamic model coupling rubb er dam collapsing model was applied to study the influence of the artificial flood on the hydraul ic characteristics in downstream Chan river, MIKE 21 and MIKE 3 Hydrodynamic model were used to study the improvement of flow and water replacement in the reasearch domain. The governing equations, numerical models and the main parameters of the model were discussed and the numerical models were validated. According to the reason why the black and stink water showing up on the downstream of Chan river and the junction of Chan river and Ba river,five dam collapsed operation schemes (collapse tme: 3h, 2h, 1h, 0.1h, 0.01h) of Chan river 12#rubber dam were proposed, aiming at raising the water dynamic in the study area by controlling the Chan river 12# rubber dam to produce artificial flood. Thus, five improved schemes were simulated and compared to analyze the improvement of flow regime and water replacement.The simulation results showed that the shorter the collapsing time, the larger the peak flood discharge, the collapse discharge is positive related to the dam water head. The downstream of the flow field in Chan river with all five schemes were analyzed, showing that the artificial flood were helpful to improve the flow regime in this area and scheme 3 (1h collapse time) has the best performance of all five schemes. The MIKE 21 two-dimensional simulation of the junction of two rivers discovered that five schemes were all helpful to the improvement of the flow regime. Considering the flow velocity, duration and the affected range,scheme 5 also showed the best performance in all schemes. To further study this situation, the MIKE 3 three-dimensional hydrodynamic model was applied in scheme 5 in the junction of two rivers, and the result showed that the water replacement has been significantly improved.