Preliminary Study On The Distribution Pattern Of Vertical Velocity And Its Influence Factors In Natural River Course

The currents in natural rivers are unsteady.In recent years,river unsteady problem increasingly prominent.Because of the unsteady flow in open channel flow itself is complicated,many characteristics of unsteady flow in open channel flow research have not been able to have a major breakthrough.Investigate the vertical flow velocity distribution type and its influencing factors of natural river course has important theoretical and engineering significance in grasp of the correct velocity vertical distribution,the bed evolution of natural river,the development of water conservancy,the port,shipping and solve actual problems such as urban flood control.In order to investigate the vertical flow velocity distribution type,this paper investigated the velocity distribution patterns respectively,and the main influencing factors were found out based on the ADV clean water experiment indoor and the measured data of Yangtze river from Pangxieqi to Huoyanqi.By using different formulas,the bedload transport rate of the river reach is calculated.By discussing the relationship between vertical velocity distribution and bed-load sediment transport rate,terrain specific discharge and flow rate,the vertical distribution types of natural river channel and their influencing factors are further clarified.The main research conclusions are as follows:(1)Through the ADV clean water experiment indoor,without the interference of external factors,the unsteady flow velocity profile of clean water is conventional that the upper flow velocity is biger and the lower flow velocity is samller,and its velocity distribution satisfies the traditional logarithmic distribution.(2)Taking the natural river course of Yangtze river from Pangxieqi to Huoyanqi as the research object,the abnormal velocity distribution can be summed up as 7 types: "3","C"," anti C","1","S","7",and " anti S" based on a large amount of measured velocity data.(3)Preliminary analysis shows that the "7" vertical velocity of flow appears mostly at where the topography rise suddenly.The "1" vertical velocity of flow appears mostly at the center of the riverbed depression.The "C" type of vertical velocity often appeared in the river is constricted along the direction of the stream,where the flood peak rising steeply,the exit of chamfer and harbor basin.The " anti C" type of vertical velocity often appeared in the the backwater end of the reservoir,the river is broadening along the direction of the stream,where the flood peak fell steeply,the entrance of chamfer and harbor basin.The "S" type and "anti S" type vertical flow velocity appear mostly in the vegetated area of the channel near shore.(4)The distribution of vertical velocity distribution in the researched river is mostly "3" shape.This velocity distribution pattern mostly appears in the main channel area of the river where terrain is flat.The preliminary analysis shows that the turbulent flow of natural river channel is the main reason for the formation of this distribution pattern.(5)In the vertical average,maximum velocity and bed-load sediment transport rate relationship analysis,the research of the vertical average,maximum velocity and bed-load rate changes has good consistency,the two into a strict linear relationship.(6)In the vertical average,maximum velocity and vertical and horizontal topographic of riverbed relationship analysis,the vertical average,maximum velocity of the researched river and the change of vertical and horizontal gradient of the riverbed are in good agreement.The vertical average velocity is strictly related to the vertical gradient of riverbed,and has a poor correlation with the cross gradient of riverbed.(7)By comparing and analyzing the vertical average velocity and the maximum velocity of the flow at different flow rates,the vertical average velocity and the maximum velocity of the vertical are increased with the increase of the flow rate.The amplification of average velocity and maximum velocity of each section are different,.Preliminary analysis shows that this is due to the different shapes of the cross sections and the changes of the topography of the upper and lower reaches of each section.