Study Of Sediment Transport And Water Temperature Distribution In Daliushu Reach Of The Yellow River

The sediment concentration of the Yellow River is world famous.In the natural evolution process,the Yellow River is not only changes along the vertical direction,but also has the characteristic of horizontal swing in the plane.In this thesis,the research object is the Daliushu reach of the Yellow River.The river belongs to the bend channel with the change of water and sand.The mainstream is wander and the erosion-accretion variation is severe.The proposed Daliushu Hydro Project located at the outlet of heishan gorge on the Yellow River at the junction of the Gansu Province and Ningxia Hui Autonomous Region.The project has a very important significance in the industrial and agricultural production and economic and social development at Northwest underdeveloped areas and the minority areas.On this basis combined with riverbank erosion mechanics built three-dimensional mathematical model for the river bed evolution in the Daliushu reach.The flow movement,river bed evolution and the river bank swing were measured and calculated before Daliushu dam construction.The one-dimensional and two-dimensional water temperature numerical model are used to simulate the water temperature distribution and freezing point position in the Ningxia-Inner Mongolia and downstream of the dam after the completion of the Daliushu reservoir.The research results can provide reliable theoretical basis to reasonable run of Daliushu reservoir,reduce deposition and ice prevention of Ningxia-Inner mongolia reach of Yellow River.The three-dimensional turbulent numerical model was established based on triangular mesh.The governing equations are discreted using unstructured mesh finite volume method and solved using SIMPLE algorithm on unstructured grids.The flow movement are simulated in continuous curve of Shapotou reach of the Yellow River.The plane flow field,the longitudinal velocity distribution and transverse velocity distribution are obtained.By comparison,the measured results are well consistent with the computational results.It indicates that the model can be used to simulate the characters of bend flow in natural rivers with complex boundary.Based on the 3-D turbulent flow model,the three-dimensional mathematical model of river bed evolution was established considering the bank erosion mechanical mechanism and bank shape correction technique.The model is used to simulate the riverbed evolution of the Daliushu reach in Yellow River.The results show that the calculated values are in good Agree-ment with the measured values,indicating that the established riverbed evolution model can refl ect the evolution rules of Daliushu reach flow and the riverbed deformation.As a result of the upstream flow and sediment conditions different,the Daliushu reach erosion and associated with horizontal swing during in November 2011 to October 2012.The maximum thrust deep up to 2.5m on the reach.In the curve region,concave bank erosion was more serious than convex bank,the deep groove moved to the concave position.It shows that the curve circulation was an important factor for the horizontal evolution of the river channel.The one-dimensional and two-dimensional water temperature mathematical model are established of the downstream in Daliushu dam.The temperature distribution and the freezing point position are simulated downstream of the dam under different weather conditions in winter.After the completion of the Daliushu reservoir,the water temperature of Ningxia reach was above 0? in winter,and the zero temperature sectional position shifts down to between Shizuishan and Dengkou,about 320km away from the Daliushu dam.The ice jam problem will be fundamental alleviated in Shizuishan to Wuhai reach.Shizuishan to Bayangaole reach will become unstable frozen river.The below Bayangaole reach will be stable frozen reach.The status of the Zhaojunfeng downstream reach will not change significantly.Thus,the use of Daliushu Reservoir has a significant role to alleviate the ice status in Ningxia-Inner mongolia reach.