Computational Research On The Flow Characteristics At The Confluences Reach Of Main Stream And Tributary Stream

The confluences of main stream and tributary stream are common in natural rivers. At the confluence zone, due to the jacking of current from main stream and tributary stream, the mixing and turbulence of current is so strong and the loss of energy is so large that the balance of water and sediment is broken which could causes sediment particle and coarse grain to deposit and forms shallow shoal at river mouth or eyot. The current state, sediment characteristic and stream bed feature are complex and changeful at main stream and tributary stream and the confluence zone. The complex of flow and topographical condition in the confluence limits the development of navigation which is paid attention by communication department. Therefore, the research on flow characteristic in the confluence of main stream and tributary stream has practical meaning.Based on the present research, this thesis analyzes the hydrodynamics characteristics in the confluence of main stream and tributary stream such as confluence pattern, flat feature, flow characteristics in the confluence zone, water surface feature, sediment movement law and evolution of river bed. Because the boundary of natural river is very difficult to be fitted in Descartes coordinate, the orthogonal body-fitted coordinate is applied in numerical model. Based on the orthogonal body-fitted grid of confluence reach of main stream and tributary stream generation, a 2-D flow mathematical model is developed by using finite volume method and SIMPLER modality to solve coupled equation which put forword by Partaker and Spalding in this thesis. The model is applied to the flow calculation of the confluence of Yangtse River and Jialing River which in the upstream of Chongqing reach and channel of Taiziji and the calculation value accords well with measured value. Moreover, this thesis also discussed some relevant problems about the confluence of main stream and tributary stream mathematical model such as the roughness in the river, the influence of turbulence characteristic.