Study On Characteristics Of Flow And Sediment Movement In Excavated Basin Of Mountainous River

In our country,China,excavated harbor basins are mostly applied to plain rivers and few are applied to mountain rivers.Due to the limitation of topography,industry on both sides and town layout,available shoreline resources are limited.The flat terrain on both sides of Qujiang River is conducive to the formation of harbor ponds by excavation,but it is also a mountainous river: the composition of riverbed is coarse,the flow varies greatly in flood season,and the water and sediment conditions are complicated.Therefore,this paper will study the feasibility of using the digged-in harbor basin layout in mountain rivers for future research and application.As a typical cecal channel,the dig-in harbor basin has backflow both in the harbor basin and in the mouth area,and the backflow varies with the main flow and the layout of the harbor basin itself.And because of the presence of the backflow of sediment into the harbor basin,will cause siltation.So the problem of sedimentation is a problem that needs to be considered in all excavated harbor basins.This paper designs mathematical models for multiple layout schemes and working conditions to fully reflect the movement characteristics of the three-dimensional water flow structure of the mountain river excavated harbor basin,and to study the pros and cons of different layout schemes.At the same time,the two-phase flow model is used to study the different layout schemes.The status and mechanism of sedimentation.get conclusion:(1)The reflux structure of the harbor basin presents a typical three-dimensional movement,and the reflux center position changes with the elevation,which indicates that the reflux of the harbor basin does not have a real vertical axis of reflux,and because of the circumferential flow passing through the reflux plane,the reflux of the excavated harbor basin is a spiral flow "inclined" up and down from a macro point of view.(2)The layout elements of the excavated harbor basin have influence on the reflux movement characteristics.With the increase of the Angle between the axis of the harbour basin and the main flow direction,the number and range of backflow in the harbour basin decrease,but the intensity of backflow increases obviously.With the increase of the width of the harbor basin,the number and intensity of backflow do not change significantly,but the expansion of the backflow area is obvious.The shape of the basin orifice has only a slight effect on the range of reflux.Moreover,the reflux intensity of the harbor basin under the large flow rate is obviously enhanced.(3)The siltation of dig-in harbor basins mainly comes from suspended sand falling and siltation,and as the angle between the axis of the harbor basin and the main flow direction and the width of the harbor basin increase,the amount of siltation also increases.The difference between the backflow intensity inside and outside the harbor basin is positively correlated with the amount of siltation inside the harbor basin.